Coadministration of tacrolimus was studied with tenofovir disoproxil fumarate and emtricitabine. Tacrolimus AUC and Cmax increased by 4% and 3%; emtricitabine AUC and Cmax decreased by 5% and 11%; tenofovir AUC and Cmax increased by 6% and 13%. No dose adjustment of tacrolimus is required.

Coadministration of tacrolimus (0.05 mg/kg twice daily) and tenofovir-DF (300 mg once daily) was studied in 21 subjects. Tenofovir Cmax increased by 13%, but AUC and Cmax were unaltered. There was no change in tacrolimus Cmax, AUC and Cmin. 

Coadministration of emtricitabine/tenofovir-DF (200/300 mg once daily) with tacrolimus (0.1 mg/kg once daily) was studied in 21 healthy volunteers. There were no significant changes in pharmacokinetic parameters for emtricitabine and tacrolimus. Emtricitabine AUC and Cmax decreased by 5% and 11%, but C24 increased by 3%. Tacrolimus AUC, Cmax and C24 increased 4%, 3% and 10%, respectively. Tenofovir AUC, Cmax and C24 increased by 6%, 13% and 11% respectively. The upper limit of the 90% CI for tenofovir Cmax was 126.5%, which was just outside the predetermined no-effect boundaries of 80-125%. However, this is unlikely to be of clinical significance given the increase in geometric mean Cmax was 13%. The study concludes that emtricitabine/tenofovir-DF can be coadministered with tacrolimus without dose adjustment in subjects with normal renal function.