Coadministration of maraviroc (100 mg twice daily) and ritonavir (100 mg twice daily) increased maraviroc AUC by 161% and Cmin by 28%. Ritonavir increases the serum levels of maraviroc as a result of CYP3A inhibition. Maraviroc may be given with ritonavir to increase the maraviroc exposure. For further information, refer to the Summary of Product Characteristics for Celsentri.
Norvir Summary of Product Characteristics, AbbVie Ltd, September 2016.

Coadministration is expected to increase maraviroc concentrations. See the complete prescribing information for maraviroc for details on co-administration of maraviroc and ritonavir-containing protease inhibitors.
Norvir Prescribing Information, AbbVie Inc, December 2016.

The maraviroc dose should be decreased to 150 mg twice daily when co-administered with potent CYP3A inhibitors. In adult patients with a creatinine clearance of <80 mL/min, who are also receiving potent CYP3A4 inhibitors, the dose interval of maraviroc should be adjusted to 150 mg once daily. In addition, maraviroc should be used with caution in adult patients with severe renal impairment (CLcr <30 mL/min) who are receiving potent CYP3A4 inhibitors. An increased risk of postural hypotension may occur in patients with severe renal insufficiency who are treated with potent CYP3A inhibitors or boosted protease inhibitors (PIs) and maraviroc due to potential increases in maraviroc maximum concentrations when maraviroc is co-administered with potent CYP3A inhibitors or boosted PIs in these patients.
Celsentri Summary of Product Characteristics, ViiV Healthcare, September 2018.

The CYP3A/Pgp inhibitor ritonavir increased the Cmax and AUC of maraviroc. Coadministration of ritonavir (100 mg twice daily) and maraviroc (100 mg twice daily) increased maraviroc AUC, Cmax and Cmin by 2.61-fold, 1.28-fold and 4.55-fold respectively (n=8). The recommended dose of maraviroc when coadministered with protease inhibitors (except tipranavir/ritonavir) is 150 mg twice daily. No additional maraviroc dose adjustment when coadministered with potent CYP3A inhibitors is required in patients with CrCl 30-80 mL/min. Maraviroc is contraindicated in patients with severe renal impairment (<30 mL/min) or ESRD on regular hemodialysis who are receiving potent CYP3A inhibitors.
Selzentry Prescribing Information, ViiV Healthcare, July 2018.