Efavirenz + Emtricitabine = Unknown or no reaction

Effect on Concentration

Efavirenz
No change
Applies within class?
No
Emtricitabine
No change
Applies within class?
No

Pharmacologic Effects

Efavirenz
Effect
N/A
Applies within class?
No
Emtricitabine
Effect
N/A
Applies within class?
No

Interaction History

N/A

Last Updated 22-Nov-2022

Summary

There was no clinically relevant drug interaction found between EFV and FTC in healthy subjects. Dose adjustments are not required when EFV is co-administered with FTC/ TAF.

Sources

Efavirenz vs emtricitabine or tenofovir ^

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

When individuals were given FTC/ TAF (400/20 mg QD) together with EFV (600 mg QD) for 14 days, EFV had no significant effect on FTC PK parameters; 90% CIs of GMRs were within the range of "no-effect" (90% CI, 0.80 to 1.25). The geometric mean ratios (GMRs; FTC/TAF + EFV / FTC/TAF) [90% CIs] of FTC were: 0.90 [0.81, 0.99] for Cmax, 0.92 [0.87, 0.96] for AUC, and 0.92 [0.86, 0.98] for Cmin.When compared to historical data, the investigators concluded that FTC/TAF did not significantly affect PK of EFV; however, no specific values were indicated.

Study Conclusions

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.