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13 FDA Veterinarian 1 (1998)

handle is hein.animal/fdavt0013 and id is 1 raw text is: 2u. 44-Lu; m Lj i I i DOUMNI I'lUUMWL January/February 1998 DOES NOT CII{U E Vol. X11, No. I FDA VETERINARL4N FDA PUBLISHES SUBSTANTIAL EVIDENCE PROPOSED RULE In the November 5, 1997, Federal Register, FDA published a proposed regulation to amend the definition of substantial evidence of effectiveness of new animal drugs. The purpose of this proposed regulation is to encour- age the submission of new animal drug applications (NADA's) and supplemen- tal NADA's for single ingredient and combination new animal drugs. The pro- posal also encourages dose range la- beling. The proposed rule implements, in part, the Animal Drug Availability Act of 1996, which amended the Fed- eral Food, Drug, and Cosmetic Act to provide for improvements in the proc- ess of approving and using animal drugs, and for other purposes. The Federal Register notice for this proposed rule is available for review or downloading on CVM's Internet Website at http://www.cvm.fda.gov/. Paper copies are available from the FDA Veterinarian. Written comments on the proposed rule must be submitted by February 3, 1998. All comments should be sent to the Dockets Management Branch (HFA-305), Food and Drug Administra- tion, 12420 Parklawn Drive, Room 1- 23, Rockville, MD 20857. Please iden- tify comments with the Docket Number 97N-0435. Questions about this rule may be directed to Herman M. Schoenemann, Center for Veterinary Medicine (HFV- 126), Food and Drug Administration, 7500 Standish Place, Rockville, MD 20855, 301-594-1638. E APPLYING PHARMACOKINETICS IN VETERINARY PHARMACEUTICALS REGULATION by Marilyn N. Martinez, Ph.D. P harmacokinetics is the study and characterization of the time course of drug concentrations within the body. These concentrations are a function of drug absorption, distribution, me- tabolism, and excretion (ADME). In turn, each of these variables is a func- tion of a drug's physico-chemical prop- erties and patient physiology. Thus, pharmacokinetics is a science that in- tegrates mathematics, biochemistry, physiology, and pharmacology. Clinical pharmacokinetics deals with the application of pharmacokinetic prin- ciples to the safe and effective thera- peutic management of patients. It ex- amines the relationship between pharmacokinetic processes and the intensity and time course of a clinical response. With the advent of clinical pharmacokinetics, practitioners have acquired a tool for individualizing dos- age regimens to accommodate interpatient variability in dose/sys- temic drug concentration/drug re- sponse. For an excellent review on this subject, readers may consult an article by Peck, et al., in Pharm. Res., 1992;9:826-833. Within the Center for Veterinary Medicine (CVM), pharmacokinetic study data have been submitted to meet a broad range of objectives. These include: * Support of applications for new chemical entities or chemical enti- ties in a new animal species: These studies tend to provide information on volume of distribution, drug clearance, extent of drug bio- availability, and estimates of the terminal elimination half life. Elimi- nation half life can be used to pre- dict the magnitude of drug accu- mulation with multiple dosing, the time needed to reach steady state, and the time needed to reduce blood concentrations to some tar- get concentration. These studies may also include information on the predictability of drug concentra- tions across a wide range of dos- ages (that is, the demonstration of linear pharmacokinetics). It may also examine the relationship be- tween dose, the drug concentra- tion/time profile, and a therapeutic (pharmacodynamic) variable. * Supplemental applications for new indications or expansion of label claims: These applications are gen- erally considered from a perspec- tive of relative bioavailability. Rela- tive bioavailability investigations are used to compare the blood concen- tration/time profiles generated by a test versus a reference treat- (Continued, next page) In This Issue Update on Drug Approvalsp in FY 97 .. .... . .......... 2 Quality Standards For Manu- facture of Animal Drugs ...... 4 Regulatory Issues in Agricul- tural Biotechnology ........... 6 FDA Programs Affecting Zoo Animal Feeds ................. 10 U.S DEPARTMENT OF HEALTH AND HUMAN SERVICES PUBLIC HEALTH SERVICE FOOD AND DRUG ADMINISTRATION CENTER FOR VETERINARY MEDICINE

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