An abstinence syndrome following chronic administration of delta-9-terahydrocannabinol in rhesus monkeys.

Chaired, chronically catheterized rhesus monkeys were administered IV delta-9-tetrahydrocannabinol (THC), 0.5 mg/kg every 6 h for 3 weeks. Following the first THC injection, the animals appeared heavy-lidded, immobile, and unresponsive to observation. Tolerance developed to these behaviors during the 3 weeks of THC administration, although the animals remained subdued compared to baseline. Following discontinuation of THC, animals showed an increase in gross movement, eye contact, and tooth baring of greater frequency and/or duration than observed before THC. This presumably represents a cannabis abstinence syndrome.