Relative cataleptic potency of narcotic analgesics, including 3,6-dibutanoylmorphine and 6-monoacetylmorphine.

Dose-response curves were constructed for duration of significant catalepsy in male Sprague-Dawley rats following i.p. administration of four established and two novel narcotic analgesics. The relative potency of the six drugs was levorphanol greater than monacetylmorphine greater than diacetylmorphine greater than dibutanoylmorphine greater than morphine greater than meperidine. Cataleptic potency correlated with analgesic potency for morphine, diacetylmorphine, and dibutanoylmorphine but not for monoacetylmorphine.