The safety profile of naltrexone in the treatment of alcoholism. Results from a multicenter usage study. The Naltrexone Usage Study Group.

BACKGROUND: Naltrexone hydrochloride is the first medication approved in the United States for the treatment of alcohol dependence in almost 50 years. This study was designed to collect safety data in a setting that reflected the expected clinical use of naltrexone. METHODS: This was a 12-week, nonrandomized, open-label usage study conducted in 40 alcoholism treatment centers throughout the United States, including free-standing alcoholism treatment programs, university clinics, Veterans Administration hospitals, and office-based primary care practices. Eligible patients were assigned, at the investigators' discretion, to a naltrexone treatment group or to a reference group that did not receive study medication. At study entry, patients must have been abstinent from alcohol for 1 to 6 weeks and enrolled in a psychosocial treatment program for alcoholism. Patients often underrepresented in controlled clinical trials, including women and patients with comorbid medical and psychiatric illness, were eligible. Patients with polysubstance abuse or infection with the human immunodeficiency virus were not excluded. RESULTS: Of 865 patients enrolled, 570 received naltrexone and 295 were in a reference group. The most common new-onset adverse clinical events in the naltrexone group were nausea (9.8%) and headache (6.6%). Naltrexone was discontinued in 15.0% of patients because of adverse events, most frequently nausea. The results of liver function tests in the naltrexone group were similar to those in the reference group. No death occurred during the study. CONCLUSIONS: This is the largest study to date describing the safety of naltrexone in a heterogeneous population of persons with alcoholism. No new safety concerns were identified.

Simulation of Na channel inactivation by thiazine dyes.

Some dyes of the methylene blue family serve as artificial inactivators of the sodium channels when present inside squid axons at a concentration of approximately 0.1 mM. The dyes restore a semblance of inactivation after normal inactivation has been destroyed by pronase. In fibers that inactivate normally, the dyes hasten the decay of sodium current. Many dye-blocked channels conduct transiently on exit of the dye molecule after repolarization to the holding potential. In contrast, normally inactivated channels do not conduct during recovery from inactivation. Kinetic evidence shows that inactivation of a dye-blocked channel is unlikely or impossible, which suggests that dye molecules compete with inactivation "particles" for the same site. In the absence of tetrodotoxin, the dyes do not affect the ON gating current unless the interpulse interval is very short. If sufficient equilibration time is allowed during a pulse, the initial amplitude of the OFF gating current is reduced to near zero. This suggests that a dye molecule is a Na channel completely blocks that channel's gating current, even the fraction that is resistant to normal inactivation. Dyes block INa and Ig with the same time course. This provides the strongest evidence to date that virtually all of recorded "gating current" is associated with Na channels. Tetrodotoxin greatly slows dissociation of dye molecules from Na channels and reduced gating current during both opening and closing of the channels.