ML23156A140

PRM-032-005 - 64FR23796 - Metabolic Solutions, Inc. Receipt of Petition for Rulemaking

ML23156A140
Person / Time
Issue date:	05/04/1999
From:	Annette Vietti-Cook NRC/SECY
To:
References
PRM-032-005, 64FR23796
Download: ML23156A140 (1)

Text

ADAMS Template: SECY-067 DOCUMENT DATE: 05/04/1999 TITLE: PRM-032-005 - 64FR23796 - METABOLIC SOLUTIONS, INC.;

RECEIPT OF PETITION FOR RULEMAKING CASE

REFERENCE:

PRM-032-005 64FR23796 KEYWORD: RULEMAKING COMMENTS Document Sensitivity: Non-sensitive - SUNSI Review Complete

Docket No.: PRM-032-005 06/14/2000 FR Cite: 64FR23796 In the Matter of Metabolic Solutions, Inc.; Receipt of Petition for Rulemaking Comment Comment Representing Docket Document Miscellaneous Accession Number Submitted By Date Date Description Number 03/15/1999 03/05/1999 Letter from M. A. Baker, Vice President, Metabolic Solutions, Inc. submitting petition for rulemaking requesting extension of regulatory distribution exemption to their product, an "Erythromicin Breath Test."

04/28/1999 04/28/1999 Federal Register Notice -

Petition for rulemaking; Notice of receipt Sam C. Augustine Self 05/20/1999 05/12/1999 2 James F. Burdick, M.D. Self 05/28/1999 05/21/1999

Docket No.: PRM-032-005 06/14/2000 FR Cite: 64FR23796 In the Matter of Metabolic Solutions, Inc.; Receipt of Petition for Rulemaking Comment Comment Representing Docket Document Miscellaneous Accession Number Submitted By Date Date Description Number 0 04/12/2000 04/05/2000 Federal Register Notice - 3674527 Denial of Petition for Rulemaking 0 06/14/2000 05/01/2000 Federal Register Notice - 0 Denial of petition for rulemaking; Correction 2

DOCKET NUMBER PETITION RULE PRM -3 ~.::- ~ I)'"'( J

. [ &1/Ff<2319") [7590-01 ! P]

Nuclear Regulatory Commission

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10 CFR Part 32 Ot

[Docket No. PRM-32--05]

AD Metabolic Solutions: Denial of Petition for Rulemaking; Correction AGENCY: Nuclear Regulatory Commission.

ACTION: Denial of petition for rulemaking; Correction.

SUMMARY

This document corrects the denial of a petition for rulemaking filed by Metabolic Solutions published in the Federal Register on April 24, 2000 (65 FR 21673). The "Addresses" section of the notice contains language that requests public comment that was inadvertently included in the notice. This action is necessary to indicate that the NRC is not soliciting public comments because the denial is the final NRC action on the petition for rulemaking.

FOR FURTHER INFORMATION CONTACT: David L. Meyer, Chief, Rules and Directives Branch, Division of Administrative Services, Office of Administration, telephone (301) 415-7162.

SUPPLEMENTARY INFORMATION: On page 21673, in the first column, the "Addresses"

• section is removed because the NRC is not soliciting public comments and the denial is the final NRC action on this petition for rulemaking .

~

Dated at Rockville, Maryland, this / clay of May 2000.

For the Nuclear Regulatory Commission.

David L. Meyer, Chief Rules and Directives Branch Division of Administrative Services Office of Administration

DOCKET NUMBER PETITION RULE PAM 3~-6'

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NUCLEAR REGULATORY COMMISSION

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[Docket No. PRM-32-05]

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Metabolic Solutions: Denial of Petition for Rulemaking AGENCY: U. S. Nuclear Regulatory Commission.

ACTION: Denial of petition for rulemaking.

SUMMARY

The U.S. Nuclear Regulatory Commission (NRC) is denying a petition for rulemaking (PRM-32-05) submitted by Metabolic Solutions. The petitioner requested that the NRC extend the regulatory distribution exemption for 1 microcurie of carbon-14 (C-14) urea to include a product being developed by its company. The product is the Erythromycin Breath Test (EBT) which uses a 111-kilobequerel (kBq) (3-microcurie) dose of C-14 erythromycin.

ADDRESSES: Submit comments to: Secretary, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001. Attention: Rulemakings and Adjudications Staff .

• Deliver comments to 11555 Rockville Pike, Rockville, Maryland, between 7:30 a.m. and 4:15 p.m. on Federal workdays.

You may also provide comments via the NRC's interactive rulemaking website (http://ruleforum.llnl.gov). This site provides the capability to upload comments as files (any format), if your web browser supports that function. For information about the interactive rulemaking website, contact Ms. Carol Gallagher (301) 415-5905 (e-mail: cag@nrc.gov).

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Copies of any comments received may be examined at the NRC Public Document Room, 2120 L Street, NW (Lower Level), Washington, DC.

FOR FURTHER INFORMATION, CONTACT: James Smith, telephone (301) 415-6459, e-mail:

jas4@nrc.gov, of the Office of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, SUPPLEMENTARY INFORMATION:

• The Petition On May 4, 1999 (64 FR 23796), NRC noticed receipt and requested comment on the PRM filed by Metabolic Solutions Inc. The comment period closed on July 20, 1999. Notice of receipt of the Metabolic Solutions PRM resulted in the NRC receiving comment letters from two medical universities in support of the petition.

The C-14 EBT measures the activity, in-vivo, of an important liver enzyme that is the most abundant drug-metabolizing enzyme in the body. This test is currently used to determine the safety of new drugs during clinical trials; as such, it is used only as a research tool. The petitioner states that the doses associated with this test are comparable to the doses for the C-14 urea test which is exempt from the requirement for licensing pursuant to 10 CFR 30.21 (a).

2

(7590-01-P]

Public Comments on the Petition The notice of receipt of the PRM invited interested persons to submit comments. The two public comments received in response to the notice, from the University of Nebraska Medical Center and Johns Hopkins Medical Institutions, were in support of the petition. The two comments generally noted the low doses associated with the test and the possible economic benefit in reducing the expense of clinical trials through elimination of the need for a byproduct materials license.

Reasons for Denial A denial is consistent with the Commission's previous decision on the C-14 urea tests to require that research be performed under a specific license (62 FR 63634], since this product is to be used only in research use. The doses are not the limiting factor for extending the distribution exemption to this test. The previous decision was based upon restrictions of such use under the common rule entitled "Federal Policy for the Protection of Human Subjects; Notices and Rules" (56 FR 28002). Although the NRC did not adopt the common rule, our intention is to follow the essential requirements of the rule, which have been adopted into 10 CFR 35.6, "Provisions for Research Involving Human Subjects." Specifically, 10 CFR 35.6 requires a licensee that conducts research involving human research subjects to obtain informed consent and obtain approval by an Institutional Review Board. Because the common rule did not allow for exemptions for research involving minimal risk, the Commission 3

determined that such research use should not be exempt from 10 CFR 35.6.

Dated at Rockville, Maryland, this 5th day of April , 2000.

Fol the U.S. Nuclear Regulatory Commission.

\...,.1,SJ,w. _

William D.Traver ,

Executive Director for Operations 4

~~

~ -I Johns Hopkins f.'Ct~

Medical Institutions 600 North Wolfe Street/ Harvey 611 / Baltimore, MD 21287-8611 (410) 955-6875 /.FAX: (410) 614-2079 E-Mail: jburdic@welchlink.welch.jhu.edu *99 MAY 28 A11 :59 Department of Surgery Division of Transplantation and Vascular Surgery James F. Burdick, M.D.

Professor r May 21, 1999 DOCKET NUMBER PETITION RULE PRM 3o'Z

• S Secretary ( ~'IFR:237f~)

U.S. NUCLEAR REGULATORY COMMISSION Washington DC 20555 ATTN: Rulemakings and Adjudications Staff

Dear Secretary:

This is to provide my support for the petition by Metabolic Solutions, Inc. ( 10 CFR Part3 2, Docket No. PRM-32-5).

The C 14 erythromycin breath test has a great deal of potential, in view of the central role the cytochrome P450 process plays in the body and in pharmacology. My particular interest as a transplant surgeon involves metabolism particularly of the key drugs FK506 and cyclosporine, along with other related drugs that impact on these .

• Although not technically able to comment on the dosimetry and risks per se, it does seem that this tracer level process, which would not be likely to be used in extraordinary numbers of patients in the near future, less than 106 total tests, spread around the country, would be unlikely to produce an increase in these levels of any significant degree. Given that, I would emphasize that the potential importance of this test would seem to me warrants the agency agreeing to the petition.

Thank you for your attention to this.

Sincerely,

't1!di~

Professor of Surgery cc: Martin A Baker, Metabolic Solutions, Inc.

~owledged by card _JU_ 19 .,.,.

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ClEAR REGULATORY COMMISSIO

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n::~~0:ltlEf:ERETARY OF

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University OOCKEfE D College of Pharmacy of Nebraska 11S!~RL Department of Pharmacy Practice 986045 Nebraska Medical Center Medical Center Omaha, NE 68198-6045 (402) 559-5366 Nebraska's Health Science Center *99 MAY 20 P2 :43 A Partner with Nebraska Health System May 12, 1999 D CKi:T NUMBER Secretary PETITION RULE PRM J:?.- 5" U.S. Nuclear Regulatory Commission ( l,</F/<6131'11,)

Washington, DC 20555 Attention: Rulemaking and Adjudications Staff Regarding: Docket No. PRM-32-5 Metabolic Solutions, Inc.; Receipt of Petition for Rulemaking To Whom It May Concern:

I am writing to support the regulatory distribution exemption to the petitioner's product an "Erythromycin Breath Test"(ERMBT). I am a nuclear pharmacist and I have also been involved in clinical research trials as the Radiation Safety Officer for a contract research organization. I have supervised the use of the ERMBT in a number of new drug trials. In my experiences with the product I have not witnessed any health or safety issues with its application, nor were any reported to me. The product is unique in pharmaceutical research because of its indirect measure of cytochrome P450 3A4 activity. Sponsor organizations can determine a test drug's promotion or inhibition characteristics of this liver enzyme system with relative ease. Because the test is applied in the controlled setting of clinical trials, its use will be limited to small groups ofresearch subjects under well supervised conditions. Exposure to a large patient population is unlikely.

Exempting the ERMBT would reduce its expense as well as expedite research protocols which require its application. An added safety measure, in this instance, is the fact that Investigational Review Board approval is required in order to apply this test in clinical trials. I appreciate the opportunity to comment on this petition and urge that this product be exempted from licensing.

Sincerely,

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am C. Au~ e , RP. , Pharm.D., BCNP, FAPhA Associate Professor, Pharmacy Practice MAY Z5 1ggg l\cknowfedged by card *ee-.n,,,.. .... eeee...:;:::..

University of Nebraska-Lincoln University of Nebraska Medical Center University of Nebraska at Omaha University of Nebraska at Kearney

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DOCKET NUMBER PETITION RULE PAM 3~-S- OOCKElED

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[7590-01-P]

NUCLEAR REGULATORY COMMISSION *99 APR 28 P5 :49 10 CFR Part 32 OF ,

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[Docket No. PRM-32-5] AO,JI F Metabolic Solutions, Inc.;

Receipt of Petition for Rulemaking AGENCY: Nuclear Regulatory Commission.

ACTION: Petition for rulemaking; Notice of receipt.

SUMMARY

The Nuclear Regulatory Commission (NRG) has received and requests public comment on a petition for rulemaking dated March 5, 1999, filed by Metabolic Solutions, Inc. (petitioner). The petition has been docketed by the Commission and has been assigned Docket No. PRM-32-5. The petitioner is requesting that the NRG regulations be amended to extend a regulatory distribution exemption to the petitioner's product, an "Erythromycin Breath Test." That test uses a three-microcurie dose of carbon-14 (C14)-erythromycin to measure the rate of drug metabolism in the human liver. Current NRG regulations permit distribution of radioactive drug capsules that contain one microcurie of C14-urea to persons exempt from licensing. Dose regulations also permit any person exempt from the requirements of a license to use the capsules for diagnostic tests in humans. The petitioner believes that exempting the C14-erythromycin from regulatory control would make the breath test more widely available and reduce the costs of clinical trials without increasing the radiation risk to the public.

2 M .:; 0 1999 DATE: Submit comments by (75 days follei.e.iing p, 1blicaUon in th& ~odor:al Register).

Comments received after this date will be considered if it is practical to do so, but assurance of consideration cannot be given except as to comments received on or before this date.

ADDRESSES: Submit comments to: Secretary, U.S. Nuclear Regulatory Commission, Washington, DC 20555. Attention: Rulemakings and Adjudications Staff .

• Deliver comments to 11555 Rockville Pike, Rockville, Maryland, between 7:30 am and 4: 15 pm on Federal workdays.

For a copy of the petition, write: David L. Meyer, Chief, Rules and Directives Branch, Division of Administrative Services, Office of Administration, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.

You may also provide comments via the NRC's interactive rulemaking website through the NRG home page (http://www.nrc.gov). This site provides the availability to upload comments as files (any format), if your web browser supports that function. For information about the interactive rulemaking website, contact Ms. Carol Gallagher, (301) 415-5905 (e-mail: CAG@nrc.gov).

FOR FURTHER INFORMATION CONTACT: David L. Meyer, Office of Administration, U.S. Nuclear Regulatory Commission, Washington, DC 20555. Telephone: 301-415-7162 or Toll Free: 1-800-368-5642 or E-mail: DLM1 @NRG.GOV.

3 SUPPLEMENTARY INFORMATION:

Background

On December 2, 1997 (62 FR 63634), the NRG published a final rule in the Federal Register that permitted the distribution of radioactive drug capsules that contain one microcurie of carbon-14 (C14)-urea to persons exempt from licensing. The rule added 10 CFR 30.21 entitled, "Radioactive drug: Capsules containing carbon-14 urea for "in vivo" diagnostic use for humans," and 10 CFR 32.21 entitled, "Radioactive drug:

• Manufacture, preparation, or transfer for commercial distribution of capsules containing carbon-14 urea each for "in vivo" diagnostic use for humans to persons exempt from licensing; Requirements for a license." The rule became effective on January 2, 1998.

On March 12, 1999, the Nuclear Regulatory Commission received a petition for rulemaking submitted by the petitioner, Metabolic Solutions, Inc., a biomedical firm located in Nashua, New Hampshire. The petitioner requests that the NRG extend the regulatory distribution exemption for one microcurie of C14 urea to include an "Erythromycin Breath Test" being developed by the petitioner that contains a three-

• microcurie dose of C14-erythromycin. To do this, NRG would have to amend its regulations pertaining to the manufacture, distribution, and use of radioactive drugs in 10 CFR Parts 30 and 32.

The breath test is a tool used by researchers and physicians in the clinical study phases of drug research studies. The petitioner states that the erythromycin breath test measures the in vivo activity of a liver microsomal cytochrome P450 enzyme, CYP3A4, that metabolizes about 40 to 50% of all drugs in the body. This test is currently used in clinical research studies to help determine the safety of new drugs. Specifically, the

4 test measures the effect that drugs have on the CYP3A4 enzyme system, potential interactions with other co-administered drugs on the enzyme system, and the range of safe drug tolerance within a population. The petitioner believes that dosimetry information for the exempted C14-urea will be very similar to the results for the C14-eryth romycin.

According to the petitioner, exempting the C14-erythromycin from "regulatory control" would make the breath test more widely available and lower the costs of clinical

• trials. Also, the petitioner has concluded that the exemption would not present a radiation risk to the general public any higher than the risk associated with the distribution exemption for drug capsules that contain one microcurie of C14-urea.

(Note: The Commission has not exempted the C14-urea radioactive drug from "regulatory control." NRC requires the manufacturer and distributor to have an NRC license that authorizes the manufacture or distribution of the product to "persons exempt" from licensing under 10 CFR 30.21 or an equivalent regulation of an Agreement State.) The NRC has determined that the petition meets the threshold sufficiency requirements for a petition for rulemaking under 10 CFR 2.802. The petition has been docketed as PRM-32-5. The NRC is soliciting public comment on the petition for rulemaking.

Discussion of the Petition The petitioner believes that the NRC regulations codified at 10 CFR Parts 30 and 32 extend a regulatory exemption for drug capsules that contain one microcurie of C-14 urea. According to the petitioner, this exemption should be extended to its erythromycin breath test (ERMBT). In support of this request, the petitioner contends that the

5 dosimetry information for the exempted C14-urea capsules will be very similar to that for the ERMBT. The petitioner has provided supporting documentation for its position (Exhibit A) entitled, "Dosimetry of C14-Erythromycin." Additional supporting documentation (Exhibit B), includes: information related to the trademark, chemical ingredients, pharmacology, clinical safety, contraindications, adverse reactions, dosimetry, drug storage and stability, manufacturing procedures, analysis methodology and quality assurance procedures associated with the ERMBT.

The petitioner explains that ERMBT dosimetry data has not been collected in humans because it predates FDA regulations that govern disposition and metabolism data. In the study cited by the petitioner, dosimetry calculations were based on data collected from intravenous administration of C14-erythromycin in 10 male rats. The study found that in male rats the C14-erythromycin rapidly metabolized in the liver and that the resulting metabolite was excreted in bile. The petitioner indicates that the study also found that most radioactivity resulting from administration of the C14-erythromycin in male rats was either exhaled or excreted. The study also indicated a general

• distribution of radioactivity in various tissues of male rats after C14-erythromycin administration. The highest concentrations were present in the liver, spleen, pancreas, kidney, adrenal and submaxillary glands, lungs, and intestinal tract. Lower amounts of radioactivity were found in the skin, fat, and brain.

The rat intracellular distribution studies concluded, petitioner states, that erythromycin and its metabolites were capable of entering various cellular components of the liver. The studies also indicated that the C14-erythromycin dose emits beta radiation to exposed individuals. The Oak Ridge Institute for Science and Education,

6 Radiation Dose Information Center Radiation calculated dose estimates for humans administered C14-erythromycin. These estimates are based on data gathered in rats and are described in Appendix 1 of Exhibit A attached to the petition for rulemaking.

The petitioner indicates that data was extrapolated to humans using a weight-based extrapolation method where possible.

The petitioner believes that the information presented in Appendix 2 of Exhibit A indicates that the effective dose equivalent from the ERMBT dose (i.e. 2.1 miltirem) is

• comparable to about one-fourth of a chest X-ray and is significantly lower than other nuclear medicine tests. Estimated human organ radiation exposures are presented in Appendix 3 of Exhibit A. The highest calculated organ doses to humans from a three microcurie dosage of C14-erythromycin are 2.8 millirem to the ovaries, 2.3 millirem to the gallbladder, 1.47 millirem to the small intestine, and 0.6 millirem to the urinary bladder wall.

In Exhibit B, the petitioner notes that the ERMBT dose has been administered to patients since 1988 at the University of Michigan Medical Center. Although a few individuals reported a metallic taste in their mouths immediately after ingestion, no adverse reactions have been experienced or reported.

Because the product is used as a research tool, users of the test must receive approval from lnvestigational Review Boards to administer the ERM BT dose in clinical research studies. The petitioner states that these studies have found that allergic reactions to erythromycin are very rare. The studies also found that gastrointestinal side effects due to the erythromycin, such as abdominal pain, cramping, and mild nausea are the most common adverse reactions and are erythromycin dose related.

7 According to the studies, adverse effects are relatively infrequent in erythromycin doses that contain less than one gram of erythromycin. The petitioner notes that the ERMBT dose contains less than 0.05 milligrams and that no adverse effects have occurred with this dose amount.

According to the petitioner, the ERMBT is currently used only by researchers and physicians who can access a site that has obtained an NRC license to handle radio pharmaceuticals. The petitioner states that it is often inconvenient to use a C14 product. As stated by the petitioner, many clinical drug studies occur in physicians' offices where there is either a total ban on radioactivity or the facilities do not possess a license to use radioactive substances. The petitioner contends that the market size for the ERMBT is much smaller than that of the exempted urea test. Estimates by the petitioner are that less than 10,000 patients would receive the ERMBT between two to five times in clinical studies each year (less than 100,000 tests). The petitioner states that the C14-urea test encompassed 600,000 people who could be tested two or three times including diagnosis and follow-up testing. Without a regulatory exemption, the

• petitioner believes that the market size would be too small to be economically feasible to pursue FDA approval for the use of the ERMBT.

The Petitioner's Conclusions The petitioner concludes that dosimetry information of the C14-erythromycin will be very similar to that of the exempted C14-urea. Also, the petitioner concludes that exempting the C14-erythromycin from regulatory control will make the ERM BT more widely available and reduce clinical trial expenses. Lastly, the petitioner concludes that the exemption would not present a radiation risk to the general public any higher than

8 the risk associated with the distribution exemption for drug capsules that contain one microcurie of C14-urea.

The petitioner requests that the NRC grant a regulatory distribution exemption for the ERMBT similar to the current exemption for C14-urea capsules. This would require amending the regulations pertaining to use of radioactive drugs in 10 CFR Parts 30 and 32.

Dated at Rockville, Maryland, this c:lB:fhday of April, 1999.

For the Nuclear Regulatory Commission.

{l.,, ~ L .\/4va;;;. ~~

Annette L. Vietti-Cook, Secretary of the Commission.

DOCKET NUMBER ETITION RULE PAM 3~- .5' 460 Amherst Street

( r,'/r-R~ 31'/to)

Nashua, NH 03063 (603) 598-6960 Phone (603) 598-6973 Fax

,- :2 PH lJ: 35 Internet: http://~Wfl sol.com E-mail : metso(@ ear\hl /n,f<. ne

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j**,*0 ..... , ' 1 l.'~ NRC Dr. Donald Cool Director, Division of Industrial And Medical Nuclear Safety Nuclear Regulatory Commission Mail Stop T-8F5 Washington, DC 20555 March 5, 1999

Dear Dr. Cool,

I am writing on the advice of Dr. Anthony Tse to request your consideration to extend the regulatory distribution exemption for one microcurie of 14 C-urea (10 CFR Parts 30 and 32, RIN 3 l 50-AF70) to include a product being developed by our company. The product is the Erythromycin Breath Test that uses a three-microcuric dose of 14 C-erythromycin.

The erythromycin breath test measures the activity in vivo of an important liver microsomal cytochrome P450 enzyme called CYP3A4. CYP3A4 is the most abundant drug-metabolizing enzyme in the body. About 40 to 50% of all drugs are metabolized by this enzyme. The test is currently used in clinical studies to help detem1ine the safety of new drugs. It determines the effect that drugs have on the CYP3A4 enzyme system, potential drug interactions with other co-administered drugs, and the range of safe drug tolerance within the population. This is important infom1ation that is required by the FDA as part of the drug approval process. In the future, we hope to use the information gathered in clinical drug studies to expand the use of the test to individual drug dosing for certain difficult to dose drugs such as oncology and HIV agents.

The test is currently used only by researchers/physicians who have access to a site that has a NRC license to handle radiopharmaceuticals. Since many drug clinical studies take place in physicians' offices it is often inconvenient to use a 14 C-product. In addition, some locations have a total ban on radioactivity that only a regulatory exemption could permit. Furthermore, to extend our test's utility to include drug dosing would require the test to be conducted in a doctor's office most of whom don't have a license to use radioactive drugs. Without an exempt status the market size would be so restrictive as to make it economically impractical to pursue FDA approval for this indication.

The market size for our test is much smaller than the urea test. We estimate that the total number of patients studied in clinical trials that would use the erythromycin breath test to be less than 10,000 people annually and these people would be tested between 2 and 5 times. The use of our test for dosing drugs would unlikely exceed 100,000 tests annually. The 14 C-urea test cited a 600,000-person market and in some cases these patients would be tested 2 or 3 times (diagnosis of the bacteria and then check once or twice to confirm eradication of bacteria).

Biomedical Discovery Through Isotope Technology

lJ ..:> UCLEAR REGULATORY COMMl:xilON RlJ AKINGS &ADJUDICATIONS STAFF OFFICE OFlliE SECRETARY OF THE COMMISSION Document Smtlsllics IDs

460 Amherst Street Nashua, NH 03063 (603) 598-6960 Phone (603) 598-6973 Fax Internet: http://www.metsol.com E-mail: metsol@earthlink.net I believe that the dosimetry information for the exempted 14 C- urea will be very similar to that for the 14 C-erythromycin. I have provided dosimetry information in Exhibit A attached. In addition, I have included under the heading" investigators brochure" (See exhibit B) details on the tests applications and the manufacturing of the 14 C-erythromycin doses.

Making the 14 C-erythromycin exempt from regulatory control will make the breath test more widely available and reduce the costs of clinical trials. Furthermore, it would seem that the exemption will not increase the radiation risk to the general population anymore than that of 14C-urea .

• I appreciate your consideration of our request and look forward to your response.

Sincerely,

/~'i~-----

-~_1/-,/ /-_ ,

Martin A. Baker Vice President, Metabolic Solutions, Inc .

Biomedical Discovery Through Isotope Technology

Dosimetry of 14 C Erythromycin The erythromycin breath test (ERMBT) dose contains 3 µCi of [' 4 C-N-methyl]

erythromycin. Dosimetry data in humans has not been collected because it predates FDA regulations regarding disposition and metabolism data. Dosimetry calculations have been based solely on data obtained in male rats ( 1,2).

14 C Erythromycin distribution and excretion was studied in 10 rats after intravenous administration of [' 4 C-N-methyl] erythromycin ( 1). Erythromycin is rapidly metaholized in the liver by N-demethylation by the cytochrome enzyme P450 3A4. The resulting metabolite N-desmethyl-erythromycin is excreted in bile. The isotopic methyl group is eliminated in expired air as 14CO:,.

After 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> of administration of isotopic erythromycin in rats, about 37-43% of injected radioactivity was recovered in feces, 27-36% in the urine and 21-29% in expired air. The half-life of a single intravenously injected dose of [' .. C-N-methyl] erythromycin was 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

There was a general distribution of radioactivity in various tissues ofrats following isotopic erythromycin administration. Highest concentrations of radioactivity were found in liver, spleen, pancreas, kidney, adrenals, submaxillary glands and lungs in addition to urine, bile, feces and intestinal tract. Lower amounts of radioactivity were found in skin, fat and brain. Intracellular distribution studies indicated that erythromycin and its metabolites were capable of entering various cellular components of the liver.

The 14 C erythromycin dose emits beta radiation to exposed individuals. The radiation dose estimate for [' 4 C-N-methyl] erythromycin has been calculated by Dr. Richard Sparks, Oak Ridge Institute for Science and Education, Radiation Internal Dose Information Center. The estimate is based on data gathered in rats and a description of the model is found in Appendix 1. The total effective dose equivalent is 2.1 mrem for a 3

µCi dose of 14 C erythromycin (6.9E-01 rem/mCi). The estimated total effective dose contained in the ERMBT dose is comparable to about one-quarter of a chest x-ray and significantly lower than other nuclear medicine tests (Appendix 2). The estimated organ radiation exposures are shown in Appendix 3.

References I. Lee, C.C. et al. (1956) J. Pharmacol Exp. Ther. 117:265-273.

2. Kibwage 1.0. et al. (1989) European J Drug Metab. and Pharmacokinetics 14:7-14.

Appendix 1 Erythromycin Dosimetry Assumptions The calculation of the 14 C erythromycin radiation dose estimate in humans is based on data gathered in rats by Kibwage I. 0. et al. (European J. of Drug Metab. and Pharmacokinetics, 1989 Vol. 14, No. 1. pp.7-14.) and Lee C.C. et al. (J. Pharmacol. Exp.

Ther. 117, 1956, pp. 265-273.). The model incorporates a 64% absorption of administered activity from GI tract into the blood, based on data from Colburn W.A. et al.

(Journal of Clinical Pham1acology 17( 10 pt 1)592-600 Oct. 77). The transport of activity in the GI tract was modeled according to the ICRP 30 model. The dynamic bladder model with a 4.8-hour voiding interval was used. The radiation dose estimate was calculated using phantom of Cristy & Eckem,an (Report ORNL/TM-8381/Vl & V7).

Rat data from two sources were folded together to form a data set for IV administration of erythromycin. Where possible, these data were extrapolated to humans using a weight based extrapolation method. The absorption rate trans*er coefficient from the GI tract to blood that was found in the fitting process for the IV model, was very similar to the value that was taken from the literature source for humans, which was used in the oral model.

This coefficient, when used with the ICRP-30 GI tract model, resulted in 64% of the erythromycin being absorbed into the bloodstream. This matches nicely with a separate literature result of 70% absorption of erythromycin in rats receiving oral doses of erythromycin. The peak concentration in plasma found by the model was 1.1 % of the administered dose. This agrees very nicely with the peak plasma values for humans found in various literature sources which averaged about 1.3% of the administered erythromycin.

The doses in the walls of the Gl tract were calculated by adding the absorbed dose caused by the contents, to the absorbed dose from the activity within the walls. The effective dose equivalent (EDE) was corrected by multiplying the absorbed dose from the activity within the walls by the remainder weighting factor. The doses to the lachrymal and submaxillary glands were from self dose only, and these doses were ignored in the calculation of the EDE.

Appendix 2 Rada ti on Dosage of the Erythromycin Breath Test Compared to other Nuclear Tests Test EDE (mrem)

Extremities x-ray 1 Erythromycin Breath Test 2 Chest x-ray 8 Cervical spine x-ray 20 CT (head and chest) 111 Upper GI 244 Barium enema 406 EDE= Effective Dose Equivalent Table prepared by Dr. Richard Sparks, Oak Ridge Institute for Science and Education, Radiation Internal Dose Information Center.

Appendix 3 Organ Radiation Dose Estimates for N-Methyl- 1-1C-Erythromycin (3µCi Dose)

Organ mrad(mrem)

Adrenals 0.07 Brain 0.05 Breasts 0.05 Gallbladder Wall 2.28 Small Intestine 1.47 Stomach 0.12 Heart Wall 0.05 Kidneys 0.04 Liver 0.12 Lungs 0.05 Muscle 0.05 Ovaries 2.79 Pancreas 0.04 Red Marrow 0.07 Bone Surfaces 0.05 Skin 0.05 Spleen 0.04 Testes 0.05 Thymus 0.06 Thyroid 0.04 Urinary Bladder Wall 0.63 Uterus 0.05 Lachrymal Gland 0.18 Submaxillary Gland 0.05 Effective Dose Equivalent is 2.1 mrem for a 3 µCi dose.

Table prepared by Dr. Richard Sparks, Oak Ridge Institute for Science and Education, Radiation Internal Dose Information Center.

I. Name of Product 1.1 Tradename The tradename of the device will be known as the Erythromycin Breath Test Dose (ERMBT1mDose).

1.2 Trademark The trademark of the device is ERMBTTM Dose.

1.3 Chemical Name The chemical name of the ERMBT' Dose is (JR*, 4S*, 5S*, 6R*, 7R*, 9R*, l lR*, 12R*,

l 3S*, l 4R *)-4-((2,6-Dideoxy-3-C-methyl-3-O-methyl-a-L-ribo-hexopyranosylJ- l +dhyl-7, 12, 13-trihydroxy-3,5, 7 ,9, 11, 13-hexamethyl-6-( (3,4,6-trideoxy-3-( di- 14 C-methylamino )-b-D-

• xylo-hexopyranosyl)oxy)oxacyclotetradecane-2, 10-dione.

1.4 Common Name The common name of the ERMBTTM Dose is [ 14 C-N-methyl] erythromycin A base.

2. Radioisotope: Carbon-14

3. Active ingredients and quantity in milligrams to be administered 0.03 mg C4 C-N-methyl] erythromycin 0.40 mg (0.5 ml) ethyl alcohol, 100% USP

4. Radioactivity Administered: 3 µCi

5. Regulatory Classification The Food and Drug Administration (FDA) has determined a product jurisdiction for the erythromycin breath test (letter of March 20, 1996, RFD-96-0 I). The Center for Devices and Radiological Health (CDRH) has primary premarket review and regulation. The erythromycin breath test is subject to review under both the medical device and antibiotic drug provisions of the Federal Food, Drug, and Cosmetic Act. The ERMBTTM Dose will be used exclusively as a research tool by sponsors of clinical investigations of human drugs. The FDA will not require an investigational new dmg application (IND) for 14C erythromycin because erythromycin is regarded as a safe and effective drug (21 CFR36 l.1 ).

6. Clinical Pharmacology The ERMBTTM Dose is based on the observation that erythromycin is exclusively N-demethylated to N-des methyl erythromycin and formaldehyde by CYP3A4 as shown in liver microsomes ( 1). The carbon atom of formaldehyde appears in the breath as CO 2 (2). The ERMBT' Dose uses C4 C N-methyl] erythromycin to determine CYP3A4 activity from changes Page 1

in the rate of production of 1-1CO 2

• The radiopharrnaceutical is intravenously administered and then a single breath collection at 20 minutes is used to determine production of 14 CO 2 . The percent of drug metabolized at 20 minutes correlates with the area under the curve (AUC) of 14 CO 2 excretion over 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> (3 ). The percent of dose metabolized per hour is calculated and used to estimate CYP3A4 activity.

Several lines of evidence validate the ERMBTTM Dose as a measure of liver CYP3A4 activity.

The ERMBTTM Dose significantly correlates with the liver concentration of CYP3A4 protein in patients but not with the liver concentration of other P450 proteins (4). The ERMBT decreases with co-administration of CYP3A4 inhibitors such as troleandomycin and increases with known CYP3A4 inducers such as rifampin ( l ). The ERMBT' Dose correlates with the clearance of other CYP3A4 substrates such as cyclosporin A (5,6) and midazolam (7). During the anhepatic phase of liver transplantation, little 14 CO 2 is produced from erythromycin with the ERMBT (8),

indicating that the contribution of extra hepatic P450s to the ERMBT' Dose is minimal.

7. Clinical Safety

• The ERMBTTM Dose has been administered to patients since 1988 at the University of Michigan Medical by Dr. Paul Watkins under IND #31760. To date 1326 ERMBTTM Dose's have been administered to 591 patients. No adverse reactions have been experienced. A few patients have reported a vague "metallic" taste in their mouth immediately after the injection, but no other symptoms have been reported. There have been no IND safety reports submitted since granting the IND.

8. Indications and usage The ERMBTTM Dose contributes to a rapid, quantitative measure of in vivo cytochrome P450 3A4 (CYP 3A4) activity. The test is for professional use as an investigational tool for assessing CYP3A4 activity during pham1acological research.

There are two clinical indications for the ERMBTTM Dose. The ERMBTTM Dose is indicated for monitoring CYP3A4 activity before, during and after treatment of patients with pharmaceuticals, including new chemical entities, or other xenobiotic compounds which might alter CYP3A4 activity. The second indication for the ERMBTTM Dose is for stratifying (phenotyping) a clinical population to determine relative interpatient CYP3A4 activity during pharmacokinetic, drug metabolism and phamrncodynamic studies.

9. Contraindications The ERMBTTM Dose is contraindicated for:

• patients less than 18 years of age

• pregnant females

• nursing mothers Page 2

I 0. Precautions The ERMBTnI Dose is for investigational use only.

Users of the test are required to receive approval from Investigational Review Boards (IRBs) to administer the ERMBTTl\t Dose in clinical studies. In addition, users must either amend an Investigational New Drug (IND) application with the U. S. Food and Drug Administration (FDA) or receive approval from a Radioactive Drug Research Committee (as noted in 21 CFR 36 I. I). Users may contact Metabolic Solutions for access to the contents of a Drug Master File submitted to the FDA.

Caution: Observe Federal and State guidelines for handling radioactive material contained in this kit. Users must have a valid license to receive and use carbon-14 radioactive material and a license to administer radioactive materials to humans.

All radioactive contaminated material must be disposed by the user according to applicable

• Federal and State guidelines.

DO NOT use any sterile component of the kit that appears contaminated, leaking, tampered with or not sealed.

DO NOT use the ERMBTTI\I Dose beyond expiration date.

11. Adverse Reactions Erythromycin is a widely used antibiotic yet very few significant toxic reactions have been reported during the more than 40 years that the drug has been in use (9). Many millions of courses have been administered, but no death attributable to the medication has been recorded.

Because of this record, erythromycin is considered to be the safest antimicrobial agent available

( 10).

Gastrointestinal side effects are by far the most frequent reactions to the administration of erythromycin. Gastrointestinal side effects include abdominal pain (sometimes with cramping) flatulence, diarrhea and modest nausea with vomiting are noted most frequently. Gastrointestinal toxicity is clearly dose-related. Adverse effects are relatively infrequent with the use of <1 gram dosages. Each dose vial of ERMBTTI\I Dose contains less than 0.05 milligrams (20,000 times lower than a typical 1 gram per day erythromycin therapy). Currently, no reports of gastrointestinal side effects have occurred with this size preparation.

Allergic reactions to erythromycin are highly unusual. Hepatotoxicity of erythromycin represents a very rare event in adults. Hepatoxicity never occurs after a single dose. The most consistent abnormal laboratory finding is eosinophia, generally exceeding 500 cells/mm 3

• Serum bilirubin and alkaline phosphatase concentrations are increased in about one-half of affected individuals and transaminases are uniformly elevated. Cessation of drug administration promptly reverses signs, symptoms and laboratory aberrations. No short or long term sequelae have been detected following cessation of drug (9).

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The co-solvents used to solubilize the drug in ERMBTTM Dose are ethanol, 100% USP and Dextrose Injection, 5%, USP (added separately to vial prior to administration). Each vial contains 0.4 grams ethanol which corresponds to about 2.5% of one usual mixed drink. This amount of alcohol is trivial and would not be expected to cause any toxic reaction in patients.

The concentration of ethanol in the intravenous injection solution is about 10%, the concentration at which venous irritation can become significant. A mild venous irritation at the instillation site in some individuals may occur. The dextrose injection solution, 4.5 ml added to each vial to solubilize and dilute drug, is a trivial glucose load to the body. It is not expected to cause any toxic reaction in patients.

12. Dosimetry The ERMBT' Dose contains a 3 µCi dose of [1 4 C-N-methyl] erythromycin. Dosimetry data in humans has not been collected because it predates FDA regulations regarding disposition and metabolism data. Dosimetry calculations have been based solely on data obtained in male rats (Lee et al., J. Pharmacol. Exp. Ther. 117:265-273). 14 C Erythromycin distribution and excretion

• was studied in 10 rats after intravenous administration of [ 14 C-N-methyl] erythromycin.

Erythromycin is rapidly metabolized in the liver by N-demethylation by the cytochrome enzyme P450 3A4. The resulting metabolite N-desmethyl-erythromycin is excreted in bile. The isotopic methyl group is eliminated in expired air as 14 CO 2 .

After 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> of administration of isotopic erythromycin in rats, about 37-43% of injected radioactivity was recovered in feces, 27-36% in the urine and 21-29% in expired air. The half-life of a single intravenously injected dose of[ 14 C-N-methyl] erythromycin was 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

There was a general distribution of radioactivity in various tissues of rats following isotopic erythromycin administration. Highest concentrations of radioactivity were found in liver, spleen, pancreas, kidney, adrenals, submaxillary glands and lungs in addition to urine, bile, feces and intestinal tract. Lower amounts of radioactivity were found in skin, fat and brain. Intracellular distribution studies indicated that erythromycin and its metabolites were capable of entering various cellular components of the liver.

The 14 C erythromycin dose emits beta radiation to exposed individuals. The radiation dose estimate for [ 14 C-N-methyl] erythromycin has been calculated by Dr. Richard Sparks, Oak Ridge Institute for Science and Education, Radiation Internal Dose Information Center. The estimate is base on data gathered in rats. The total effective dose equivalent is 2.1 mrem for a 3 µCi dose of 14 C erythromycin (6.9E-01 rem/mCi). The estimated total effective dose contained in the ERMBT dose is comparable to about one-quarter of a chest x-ray and significantly lower than other nuclear medicine tests.

13. Dosage and Administration The ERMBT' Dose is intended to be administered as a sterile intravenous solution into a small hand or arm vein after dilution with Dextrose Injection, USP (5% dextrose in water).

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Prepare the ERMBTTI\I Dose as follows:

• Wear disposable gloves when preparing dose.

• Inject 4.5 ml of a 5% Dextrose Injection Solution, USP into the [ 14 C N-methyl] erythromycin dose vial and periodically allow air to escape back into the syringe to prevent pressure build-up.

• Invert vial gently 2-3 times to mix contents.

• Draw 5 ml of air into a syringe. Inject into the erythromycin vial.

• Holding the vial upside down, using a series of air for solution exchanges, draw as close to 5 ml as possible of the erythromycin/dextrose solution. Be consistent in removing as much as possible from the vial for each test. Allow the needle tip to just pierce the sepmm to obtain the last drop of solution.

• Holding the syringe upside down, draw solution from needle. Fill the syringe with about 0.5 cc air. Use the solution within 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />.

The breath test is conducted using the following procedure:

• Inject the dose of ERMBTTM Dose into the vein over a period of approximately 60 seconds, along with enough of the 0.5 cc of air to flush the tubing (to ensure complete dose administration).

• Start a 20 minute countdown after all the dose is injected into the vein.

• Remove the IV butterfly.

• Collect a breath sample at 20 minutes. Breath carbon dioxide may be trapped directly into a hyamine/ethanol solution as published by Watkins and co-workers (1) or into a breath collection device as marketed by Metabolic Solutions.

The ERMBT' Dose is not to be administered more than 10 times per year to one person.

Administration of the test ten times in one year to a person results in an estimated radiation exposure comparable to, or less than commonly used medical tests.

14. Storage and Stability of Drug Store the ERMBT' Dose dose at -20°C +/- 20°C. Avoid prolonged exposure (> 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />) to higher temperatures prior to administering dose. The erythromycin dose is stable for 1 year from the date of manufacture if stored at freezing temperatures. All vials contain the expiration date.

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15 . Manufacturing Procedures for ERMBTTM Dose Synthesis of [1 4 C-N-methyl] erythromycin The ERMBTTM Dose requires the synthesis of (1 4 C-N-methyl] erythromycin. The drug is synthesized under Good Manufacturing Practices (GMPs). All reagents are analyzed and validated. Full documentation of all steps are maintained.

The materials used in the synthesis include:

Des-N-methyl erythromycin (DuPont NEN), mol. wt 719.9 Ethyl alcohol (Quantum Chemical Company)

Palladium black (Aldrich Chemical Company, cat no. 20,583-4), atomic wt 106.4 14

[ C] Formaldehyde (DuPont NEN, cat no. NEC-039H), mol. wt. 30.03 Hydrogen gas (AIRCOO Dichloromethane (Aldrich, cat no. 27,056-3)

Methyl alcohol (Aldrich, cat no. 27,047-4)

Ammonium hydroxide, 30% NH 3 in water (Aldrich, cat no. 33,881-8)

Silica gel (Aldrich, cat no. 28,863-2)

Acetone (Aldrich, cat no. 27,072-5)

Zorbax ODS preparation column (Zorbax)

Methanol HPLC solvent (J.T. Baker, cat no. 9093-03)

Triethylammonium bicarbonate pH 7.8 (DuPont NEN)

Water (Milli-Q)

Manufacturing steps for ERMBTTM Dose Des-N-methyl erythromycin (1925 mg, 2.67 mmol), ethyl alcohol (91 ml), an aqueous solution of [1 4 C] formaldehyde (total activity 139.8 mCi, specific activity 57 mCi/mmol, 2.45 mmol),

palladium black (598.5 mg, 5.6 milliatom) were placed in a 500 ml pear shaped flask containing a magnetic stir bar. The flask was cooled in an ice bath, connected to a glass vacuum line, degassed, and filled with hydrogen gas. The contents were stirred at room temperature under the hydrogen atmosphere for 5 days. The ethanolic solution was filtered through a glass microfilter and the residue was washed with ethyl alcohol. Solvent was removed under reduced pressure at 25-30 °C. The viscous liquid was dissolved in the solvent mixture (dichloromethane:ethyl alcohol:ammonium hydroxide, 8: 1:0.025, 5 ml) and charged onto a silica gel (270 ml) column.

The silica gel column was eluted with 150 ml of the solvent mixture, capped and stored overnight. The product was purified by gravity column using the above solvent mixture and 15 ml fractions were collected. The product was rechromatographed as described above. The viscous liquid obtained after column chromatography was crystallized from acetone (12 ml).

The crystals were collected by decanting the mother liquors. The solid material was purified by preparative HPLC using a Zorbax ODS column, 10 mM triethylammonium bicarbonate pH 7.8 /

methanol gradient. The purified C4 C-N-methyl] erythromycin, (465 mg, 32 mCi, 0.63 mmol, 23% yield), is dissolved in ethyl alcohol (320 ml) to get 0.1 mCi/ml solution. Material is placed in NENSURE vials and stored at -20 °C.

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Sterilization, Filling, and Sealing of ERMBTTM Dose Finished Product The product is packaged in compliance with the current Good Manufacturing Practices as set forth in the Code of the Federal Regulations, Section 21 parts 210 and 211. Current standard operating procedures are followed during each manufacturing process .

a) Formulation 500 µCi 14 C Erythromycin in ethanol Ethyl alcohol 100%, USP b) Container, closure, and packaging Vial: 5 ml clear, 20 mm opening, USP Type 1 glass Stopper: 20 mm, 4416/50 gray butyl teflon-coated Seal : 20 111111 , white, flip-off

16. Specific techniques to analyze and quantify the radiopharmaceutical The radiochemical purity of the radiopharmaceutical was checked by TLC using a solvent system of Jichloromethane, methanol and ammonium hydroxide [75:25:0.05]. The relative purity was estimated after autoradiography by comparing the intensity of any impurities visible in the sample lane to either a) the intensity of 5% of the activity chromatogrpahed in an adjacent lane, or b) the intensity of 5% spotted on the plate above the solvent front. The identity of the product was confirmed by cochromatography with a visualized authentic standard.

Additional radiochemical purity checks were determined by high performance liquid chromatography (HPLC) using a Zorbax SB-C 18 250 x 4.6 mm column. The mobil phase was methanol/0.01 M KH 2PO 4 pH7.5 /diethylamine (75/25/0.05) and the flow rate was 1.0 ml/min .

The radiochemical detection was by Packard components using Pico-Fluor 40 as scintillant and UV detection was 214 nm. The run time was 40 minutes. 25 µl of labeled compound was injected or 5 µl of each unlabeled standard .

Mass spectral analysis of the radiopharmaceutical was used to determine the specific activity.

The mass spectral analysis of [ 14 C] erythromycin was conducted on a Kratos MS25RF mass spectrometer. Fast Atom Bombardment (F AB) was used for ionizing the compound. Xenon was used as the bombarding nuclei. Glycerol was used as the matrix in the F AB experiment.

The radioactivity of the pharmaceutical was determined by mass spectrometry and liquid scintillation counting.

A 25 µ1 aliquot (in duplicate) was withdrawn from each vial tested and placed directly into a liquid scintillation vial containing 3 ml Formula 989 universal LSC cocktail (containing 2.5% by volume solvable). All vials were counted in a Beckman model LS 6000TA beta liquid scintillation counter.

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17. Results of analysis of bulk radiopharmaceutical Radionuclidic purity = 99%

Radiochemical purity= 99%

Specific activity= 50.5 mCi/1111110!

18. Method of assaying activity of finished product A subset of prepared radiopharmaceuticals are assayed in duplicate for radiochemical purity by HPLC as described above. The radioactivity of each of these vials are assayed by beta liquid scintillation counting as described above.

19. Stability of Product The erythromycin is stored in ethanol at -20 °C. Current stability tests indicate at least a 1 year expiration date from manufacturing date.

20. Quality assurance procedures for sterility, apyrogenicity and radiochemical purity.

Final doses of the injectable radiopharmaceutical are assayed for the presence of bacterial and fungal contaminants in accordance with USP 23. Sterility testing are performed by Microbiological Associates, Inc., Bethesda, MD. Apyrogenicity is measured by a kinetic-QCL endotoxin test by Oread Laboratories, Inc., Lawrence, KS 66047. The radiochemical purity of the final sterile product is tested using HPLC analysis as described above .

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21. References

1. Watkins, PB, Murray SA, Winkelman LG, Heuman DM, Wrighton SA, Guzelian PS. (1989)

Erythromycin breath test as an assay of glucocorticoid-inducible liver cytochromes P-450:

Studies in rats and patients. J. Clin. Invest. 83:688-697.

2. Baker AL, Ko take AN, Schoeller DA. ( 1983) Clinical utility of breath tests for the assessment of hepatic function. Semin. Liver Dis . 3:318-329.

3. Turgeon DK, Leichtman AB, Blake DS, Schmouder RL, Lown K, Watkins PB (1994)

Prediction of interpatient and intrapatient variation in OG 37-325 dosing requirements by the erythromycin breath test. Transplantation 57:1736-1741.

4. Lown K, Kolars J, Turgeon DK, Merion R, Wrighton SA, Watkins PB. (1992) The erythromycin breath test selectively measures P450III in patients with sever liver disease.

0 Clin. Pharmacol. Ther. 51 :229-238 .

• 5. Watkins PB, Hamilton TA, Annesley TM, Ellis CN, Kolars JC, Voorhees JJ. (1990) The erythromycin breath test as a predictor of cyclosporine A blood levels. Clin. Pharmacol.

Ther. 48:120-129 .

6. Stein CM, Kinirons MT, Pincus T, Wilkinson GR, Wood AJ. (1990) Comparison of the dapsone recovery ratio and the erythromycin breath test as in vivo probes of CYP3A activity in patients with rheumatoid arthritis receiving cyclosporine. Clin. Pharmacol. Ther. 59:47-51.

7. Lown KS, Thummel KE, Benedict PE, et al. (1995) The erythromycin breath test predicts the clearance ofmidazolam. Clin. Pharmacol. Ther. 57:16-24.

8. Watkins PB, Turgeon DK, Saenger P, Lown KS, Kolars JC, Hamilton T, Fishman K, Guzelian PS, Voorhees JJ. (1992) Comparison of urinary 6-b-cortisol and the erythromycin breath test as measures of hepatic P450IIIA (CYP3A) activity. Clin. Pharmacol. Ther.

52:265-273 .

9. Eichenwald HF . (1986) Adverse reactions to erythromycin. Pediatric Infectious Disease 5:147-150.

10. Ginsburg CM, Eichenwald HF. (1976) Erythromycin: A review of its uses in pediatric practice. J Pediatr 89:872-74.

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