There was no clinically relevant drug interaction found between EFV and TAF in healthy subjects. Dose adjustments are not required when EFV is co-administered with FTC/TAF or with TAF as a stand-alone agent.
Efavirenz vs emtricitabine or tenofovir
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Study Design
In a fixed-sequence, crossover study, the concomitant use of tenofovir alafenamide fumarate (TAF; formerly known as GS-7340) and efavirenz (EFV) was evaluated in healthy subjects (n=12). Subjects received a co-formulated fixed-dose combination (FDC) of emtricitabine (FTC) /TAF 200/40 mg once daily (QD) for 12 days (Days 1-12), followed by co-administration of FTC/TAF 200/40 mg QD and efavirenz (EFV) 600 mg QD for 14 days (Days 13-26). Pharmacokinetic (PK) sampling was performed on Days 12 and 26.
Study Results
Coadministration with EFV (600 mg QD) resulted in slightly decreased PK parameters of both TAF and tenofovir (TFV\p\g however, the magnitude of these changes was not considered as clinically significant. The geometric mean ratios (GMRs; FTC/TAF + EFV / FTC/TAF) [90% CIs] of TAF were: 0.78 [0.58,1.05] for Cmax and 0.86 [0.72,1.02] for AUC GMRs (FTC/TAF + EFV / FTC/TAF) [90% CIs] of TFV were: 0.76 [0.67,0.86] for Cmax, 0.80 [0.73,0.87] for AUC, and 0.82 [0.75, 0.89] for CminWhen compared to historical data, the investigators concluded that FTC/TAF did not significantly affect PK of EFV; however, no specific values were indicated.
References
S Ramanathan, H Wang, J Custodio, M Hepner-Harris, A Cheng, BP Kearney. Lack of clinically relevant drug interactions between gs-7340 and efavirenz. abstract p_09. 13th International Workshop On Clinical Pharmacology Of Hiv Therapy. Barcelona, Spain. ; 2012.
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