Reinforcing effects of oral Δ⁹-THC in male marijuana smokers in a laboratory choice procedure

Abstract

Rationale

Oral Delta-9-tetrahydrocannabinol (Δ⁹-THC; Marinol) is medically available for the treatment of nausea associated with cancer chemotherapy and for wasting syndromes related to HIV/AIDS. Little is known about its reinforcing effects.

Objective

This study was conducted to characterize the reinforcing effects of oral Δ⁹-THC in experienced marijuana smokers under controlled laboratory conditions.

Methods

Ten healthy male marijuana users completed this 17-day residential study. On days 2, 6, 10, and 14, at 0900 h, participants received a “sample” oral dose of Δ⁹-THC (0, 10, 20 mg) and an alternative reinforcer, a $2 voucher (redeemable for cash at study’s end). Over the next 3 days, they had 11 opportunities to self-administer either the sampled dose of Δ⁹-THC or to receive a $2 voucher.

Results

Participants chose active Δ⁹-THC (10 and 20 mg) more often than placebo (<two selections vs ∼four selections, respectively). However, they chose active Δ⁹-THC on less than 50% of choice opportunities. Both active Δ⁹-THC doses produced significant increases in “positive” subjective effects, impaired psychomotor performance, and increased heart rate, relative to the placebo conditions.

Conclusion

These data indicate that oral Δ⁹-THC may have modest abuse liability in experienced marijuana smokers.