Pharmacokinetics, Safety, and Tolerability of Phentermine in Healthy Participants Receiving Taranabant, a Novel Cannabinoid-1 Receptor (CB1R) Inverse Agonist

This study assessed the potential pharmacokinetic interaction and safety/tolerability of taranabant and phentermine coadministration. This was a randomized, double-blind, 3-panel, fixed-sequence study in healthy participants. Panels A, B, and C evaluated the safety/tolerability of phentermine 15 mg coadministered with taranabant 0.5, 1, and 2 mg for 7 days (panel A) and 28 days (panels B and C). In panels A and C, phentermine 15 mg was administered both with (7 days, panel A; 28 days, panel C) and without (7 days) taranabant 0.5 mg or 2 mg to evaluate pharmacokinetics. The primary endpoint was phentermine AUC(0-24) h in panels A and C. Secondary endpoints were changes from baseline in blood pressure and heart rate for all panels. The geometric mean ratios and 90% confidence intervals for phentermine AUC(0-24) h in the presence/absence of taranabant 0.5 mg and 2 mg were 1.08 (0.99, 1.17) and 1.04 (0.98, 1.10), respectively. No significant differences in blood pressure and heart rate were observed with any treatment versus placebo. Coadministration of taranabant 0.5 mg, 1 mg, and 2 mg with phentermine was well tolerated with no pharmacokinetic interaction and did not result in meaningful changes in blood pressure or heart rate versus placebo.