Abstract

Naloxone (Narcan - Winthrop), the N-allyl derivative of oxymorphone, is a narcotic antagonist whose most important clinical property is reversal of narcotic-induced respiratory depression. Like nalorphine (Lethidrone - Wellcome) and levallorphan (Lorfan - Roche), it also antagonises the sedative, analgesic and miotic effects of narcotic analgesics.¹ There is, however, an important difference. When not preceded by the administration of a narcotic or when given in excess, nalorphine and levallorphan themselves have narcotic effects; by contrast, naloxone has none.² It is, for all practical purposes, a pure antagonist, whereas nalorphine and levallorphan are partial agonists, with agonist as well as antagonist effects.³