Naltrexone, an Antagonist for the Treatment of Heroin Dependence

TLDR

Naltrexone is a highly potent, orally effective opioid antagonist, 17 times stronger than nalorphine, lacking agonistic activity and with a duration of action between naloxone and cyclazocine. In a 50 mg/day dose, naltrexone produced blockade of morphine and heroin comparable to 4 mg/day cyclazocine, indicating it is a potent, pure antagonist that could be useful for treating heroin and narcotic dependence.

Abstract

Naltrexone (EN-1639A) is approximately 17 times more potent than nalorphine as an antagonist in man. It is virtually devoid of agonistic activity, including the ability to induce nalorphine-like dysphoric effects. Its duration of action is longer than that of naloxone, but shorter than that of cyclazocine. It is effective orally. When administered in a dose level of 50 mg/day, it produces a degree of blockade of the effects of morphine and heroin that is comparable to that obtained with 4 mg of cyclazocine per day orally. Naltrexone, thus, appears to be a relatively pure potent narcotic antagonist which is effective orally and which may have utility in the treatment of heroin and narcotic dependence.