Maraviroc dose should be decreased to 150 mg twice daily when co-administered with a PI other than tipranavir/ritonavir (coadministration with fosamprenavir/ritonavir is not recommended). Coadministration of atazanavir (400 mg once daily) and maraviroc (300 mg twice daily) increased maraviroc AUC by 3.57-fold and Cmax by 2.09-fold. Atazanavir concentrations were not measured, but no effect is expected. Coadministration of atazanavir/ritonavir (300/100 mg once daily) and maraviroc (300 mg twice daily) increased maraviroc AUC by 4.88-fold and Cmax by 2.67-fold. Atazanavir/ritonavir concentrations were not measured, but no effect is expected. When given with atazanavir/ritonavir to patients with impaired renal function (creatinine clearance <80 ml/min), maraviroc should be reduced to 150 mg every 24 h.
Celsentri Summary of Product Characteristics, ViiV Healthcare, October 2013.

The CYP3A/Pgp inhibitor atazanavir increased the Cmax and AUC of maraviroc. Coadministration of atazanavir (400 mg once daily) and maraviroc (300 mg twice daily) increased maraviroc AUC, Cmax and Cmin by 3.57-fold, 2.09-fold and 4.19-fold, respectively (n=12). Coadministration of atazanavir/ritonavir (300/100 mg once daily) and maraviroc (300 mg twice daily) to 12 subjects increased the AUC, Cmax and  Cmin of maraviroc by 4.88-, 2.67-, and 6.67-fold, respectively. The recommended dose of maraviroc when coadministered with protease inhibitors (except tipranavir/ritonavir) is 150 mg twice daily. Coadministration is not recommended in patients with creatinine clearance <30 ml/min or on haemodialysis.
Selzentry Prescribing Information, ViiV Healthcare, September 2013.

The effect of atazanavir alone (400 mg once daily) or atazanavir/ritonavir (300/100 mg once daily) on the pharmacokinetics of maraviroc (300 mg twice daily) was studied in 12 HIV- subjects. Atazanavir alone increased maraviroc AUC by 3.6-fold and Cmax by 2.1-fold; atazanavir/ritonavir further increased maraviroc AUC (4.9-fold) and Cmax (2.7-fold). There were no significant safety or toleration issues. Maraviroc dose should be decreased to 150 mg twice daily when given with atazanavir or atazanavir/ritonavir.
An investigation of the effects of atazanavir and ritonavir boosted atazanavir on the pharmacokinetics of the novel CCR5 inhibitor UK-427,857. Muirhead G, et al. 7th International Congress on Drug Therapy in HIV Infection, Glasgow, November 2004, abstract P283.

PIs + Efavirenz
Maraviroc dose should be decreased to 150 mg twice daily when co-administered with efavirenz in the PRESENCE of a PI (other than tipranavir/ritonavir where the dose should be 600 mg twice daily). Efavirenz and atazanavir/ritonavir has not been studied. Based on the extent of inhibition by atazanavir/ritonavir in the absence of efavirenz, an increased exposure is expected.
Celsentri Summary of Product Characteristics, ViiV Healthcare, October 2013.