DUPONT's MALTREXONE: PRELIMINARY FDA APPROVAL ON PHARMACOLOGICAL MECHANISM

DUPONT's MALTREXONE: PRELIMINARY FDA APPROVAL ON PHARMACOLOGICAL MECHANISM of action is being considered, FDA told its Drug Abuse Advisory Cmte. Feb. 3. FDA Neuropharmacological Div. Director Paul Leber, MD. said the agency is preparing to recommend the approval of naltrexone "for the blockade of the effects of exogenous opiates in detoxified, formerly dependent narcotic addicts as adjunct to the maintenance of the opiate free state." He emphasized that that indication is "precisely what we believe the evidence can support, no more." "You may not realize its unusual to have that kind of [pharmacologic action] indication," Leber explained. "As a rule, the agency does not approve products because of [their] pharmacological mechanism of action." For instance, Leber noted that narcotics are approved as analgesics, not because they have agonistic effects as opiate receptors, but because of efficacy rates. Leber said the most recent drug product that is analagous to naltrexone is Nicorette, the smoking deterrent approved by FDA Jan. 13. "It was not approved because it supplies nicotine at a level [approaching] that supplies by cigarettes, but because [the sponsors] could demonstrate from controlled clinical trials that it cut or changed the quit rates between placebo . . . in a particular type of setting." FDA asked the cmte. whether it concurred with the agency's proposal to approve naltrexone for the limited indication. The agency noted that approval would be conditioned upon the pending demonstration that naltrexone has a sustained ability to act as a narcotic antagonist (i.e., after six months or more of use). The cmte. unanimously supported FDA's decision. However, cmte. members indicated some concerns about approval. Cmte. member Mitchell Balter, PhD, Natl. Institute of Mental Health, said he would find it "very difficult to say I want to throw this [drug] in the marketplace for some use among some kind of addicts under some circumstances for some length of time" when "we lack safety data, particularly in the long run." He added that if naltrexone is approved the agency should make clear the uncertainty of maintaining people on naltrexone for a long time. Leber said the agency was not "as sure as we would like to be about the level of" naltrexone's safety. "We have a reduced database, one that is not documented as well as we would like and although we've seen nothing dangerous in the database . . . this database was presented in a way that makes us wonder about what the upper limit of risk actually is," Leber stated. Cmte. member Joseph Schoolar, MD/PhD, Texas Medical Center, recommended that insert material "include a statement that the liver function needs to be" cleared up. Cmte. member Reese Jones, MD, University of California at San Francisco, added that "besides liver function there's a number of subtle, almost undefinable comparable effects which should be monitored" after a certain amount of drug use.