Effect of delta-9-tetrahydrocannabinol on intraocular pressure in humans.

As early as 1971, it was noted that smoking marijuana lowered intraocular pressure. In this study one of the active components of marijuana, delta-9-tetrahydrocannabinol, was given intravenously to ten subjects with normal intraocular pressures. Two strengths were used--0.022 mg/kg of body weight and 0.044 mg/kg of body weight. Intraocular pressure was found to decrease as much as 51% of baseline normal with an average decrease of 37%. Heart rate increased in a range of 22% and 65% of the resting pulse. Respiratory rate was not affected. No analgesic properties were demonstrated by either cutaneous or periosteal stimulation. Anxiety levels were increased by delta-9-tetrahydrocannabinol over placebo and diazepam (Valium). The mechanism of action is still uncertain but it is believed by some workers to be similar to that of a beta-adrenergic stimulator.