Nature 224, 1226 (20 December 1969); doi:10.1038/2241226a0

Some Effects of a Hallucinogenic Compound (Cyprenorphine Hydrochloride; M 285) on the Light Reinforced Behaviour of Rats

G. LOWE & D. I. WILLIAMS

Department of Psychology, University of Hull.

CYPRENORPHINE hydrochloride (M 285)¹ is a morphine antagonist with greater potency (about 35 times) parenterally and longer duration of action than nalorphine. It has been surveyed for psychotomimetic effects in groups of five to ten pre-operative patients in the USA. After an intramuscular dose of 0.5 mg/kg about half claimed a "crazy feeling" or "seeing things", usually with their eyes closed, and an irrational fear. These effects were more severe after 1.0 mg intramuscularly with distinct hallucinations in three of ten patients (personal communication from A. L. A. Boura).

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