Propranolol effects on acute marihuana intoxication in man.

To investigate the possible interaction of a beta adrenergic blocking agent and marihuana, six healthy experienced marihuana smokers received the two drugs separately and in combination. Propranolol (120 mg per os) reduced resting HR and BP; there were no changes in performance on tasks designed to test psychomotor speed, attention, memory and learning. Marihuana (10 mg delta9-THC), administered in smoke, induced the typical subjective state ("high") with marked increases in HR, BP and conjunctival injection; it impaired performance on a learning test without significantly affecting attention. Pre-treatment with propranolol blocked effectively the cardiovascular effects of marihuana; it prevented the learning impairment and, to a lesser degree, the characteristic subjective experience.