Nalorphine clinical potency

The disclosure that the antagonist nalorphine was a potent analgetic led to the synthesis of a number of 6,7-benzmorphans that were clinically evaluated as to analgesia, psychotomimetic effects, and the existence of other opioid effects. Phenazocine, which demonstrated high potency but no antagonism, was already mentioned. Cyclazocine, with... 

From the pharmacological and clinical side, little progress had been made, except that it was much easier to determine clinical activity and physical dependence liability. However, in 1954, Beecher and Lasagna made the remarkable discovery, confirmed by Keats and Telford in 1956, that nalorphine, a narcotic antagonist, was an analgesic in man comparable in potency to morphine. This observation took an added significance when it was recalled that nalorphine was ineffective in the hot-plate and tail flick tests. 

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