Pharmacokinetic interaction of ritonavir-boosted elvitegravir and maraviroc

The pharmacokinetic (PK) interaction between ritonavir-boosted elvitegravir (elvitegravir/r) and maraviroc was evaluated.

Healthy subjects were randomized to receive elvitegravir/r (150/100 mg once daily) before or after elvitegravir/r plus maraviroc (150 mg twice daily) (group 1; n = 20) or receive maraviroc before or after maraviroc plus elvitegravir/r (group 2; n = 16). All regimens were administered for 10 days and elvitegravir, ritonavir, and maraviroc PK determined. Lack of PK alteration was defined as 90% confidence intervals for ratio of geometric least squares means ratio (coadministration:alone) between 70% and 143% for elvitegravir and ritonavir Cmax (maximum concentration), Ctau (trough), and AUCtau (area under plasma concentration-time curve; 0-24 hours); for maraviroc, given a 100% increase in Cmax and AUCtau (0-12 hours); the predicted 90% confidence intervals were 162% to 247% and 136% to 295%, respectively.

Twenty-eight of 36 enrolled subjects completed the study; one discontinuation was due to an adverse event. The most common adverse event across treatments was headache. Upon coadministration, elvitegravir and ritonavir PK were unaltered, but maraviroc exposures were 2-fold to 4-fold higher presumably due to ritonavir-mediated CYP3A-/Pgp inhibition.

During elvitegravir/r plus maraviroc administration, no elvitegravir or ritonavir dose change and a reduced 150-mg dose of maraviroc are recommended.