Purpose: The purpose of this study was to evaluate the effect of the African potato (AP) on the pharmacokinetics of efavirenz. METHODS; A single-dose, two-phase sequential study was conducted over 31 days in 10 healthy volunteers. On day 1 of the study, volunteers were administered a 600 mg efavirenz tablet, and blood samples were collected before dosing and at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 8, 12, 18, 24, 36 and 48 hours after dosing. From day 16, a traditionally prepared AP decoction was administered daily until day 30. On day 29, volunteers were administered a single 600 mg dose of efavirenz, as was done on day 1. Plasma samples were harvested immediately after blood sample collection and frozen at -80 degrees C until assayed. Plasma concentrations of efavirenz were determined by a validated high performance liquid chromatography (HPLC) method with UV detection, and pharmacokinetic parameters were calculated. Geometric mean ratios of C(max) and AUC(0-48) of efavirenz before and after co-administration of 14 successive daily doses of AP were compared.
Results: All subjects completed the study. The geometric mean ratios of C(max) and AUC(0-48) were 97.30 and 102.82 with corresponding 90% confidence intervals (CIs) of 78.81 - 120.14 and 89.04 - 118.80, respectively.
Conclusion: Pharmacokinetic data generated during this study indicated that AP did not significantly alter the pharmacokinetics of efavirenz. Hence, co-administration of AP is unlikely to affect the clinical usage of efavirenz.