Bioavailability study of dronabinol oral solution versus dronabinol capsules in healthy volunteers.

BACKGROUND

Dronabinol, a pharmaceutical Δ-9-tetrahydrocannabinol, was originally developed as an oral capsule. This study evaluated the bioavailability of a new formulation, dronabinol oral solution, versus a dronabinol capsule formulation.

METHODS

In an open-label, four-period, single-dose, crossover study, healthy volunteers were randomly assigned to one of two treatment sequences (T-R-T-R and R-T-R-T; T = dronabinol 4.25 mg oral solution and R = dronabinol 5 mg capsule) under fasted conditions, with a minimum 7-day washout period between doses. Analyses were performed on venous blood samples drawn 15 minutes to 48 hours postdose, and dronabinol concentrations were assayed by liquid chromatography-tandem mass spectrometry.

RESULTS

Fifty-one of 52 individuals had pharmacokinetic data for analysis. The 90% confidence interval of the geometric mean ratio (oral solution/capsule) for dronabinol was within the 80%-125% bioequivalence range for area under the plasma concentration-time curve (AUC) from time zero to last measurable concentration (AUC) and AUC from time zero to infinity (AUC). Maximum plasma concentration was also bioequivalent for the two dronabinol formulations. Intraindividual variability in AUC was >60% lower for dronabinol oral solution 4.25 mg versus dronabinol capsule 5 mg. Plasma dronabinol concentrations were detected within 15 minutes postdose in 100% of patients when receiving oral solution and in <25% of patients when receiving capsules.

CONCLUSION

Single-dose dronabinol oral solution 4.25 mg was bioequivalent to dronabinol capsule 5 mg under fasted conditions. Dronabinol oral solution formulation may provide an easy-to-swallow administration option with lower intraindividual variability as well as more rapid absorption versus dronabinol capsules.