Summary of interactions between vivriviroc and other ARVs

A recently published review on vicriviroc contains a section summarising the metabolism of the compound (primarily metabolised by CYP3A4; not inducer or inhibitor of CYP3A4; not a substrate for P-gp) and drug-drug interactions.

Since vicriviroc is extensively metabolised the exposure is increased when given with ritonavir. In Phase II trials optimal dosing was achieved by co-administration with a ritonavir-boosted PI as part of the regimen (30 mg once daily with ritonavir based regimen). Drug-drug interactions have been investigated between vicriviroc plus ritonavir and 11 other antiretrovirals (atazanavir, darunavir, fosamprenavir, indinavir, nelfinavir, saquinavir,
tipranavir, lopinavir, zidovudine/lamivudine and tenofovir).

None of the agents evaluated required dose modification or monitoring when co-administered with vicriviroc; nor does vicriviroc require dose modification when given with any of the 11 agents. In contrast due to the inducing effect of efavirenz, co-administration of vicriviroc alone with efavirenz is not recommended.

Other interactions described are with midazolam, ketoconazole, rifabutin (increase ritonavir dose), rifampicin (not recommended), carbamazepine (increase ritonavir dose) and the oral contraceptives ethinyl estradiol and norethindrone (interaction needs careful monitoring due to the ritonavir effect).

Ref: Kummerle T et al. Vicriviroc: a CCR5 antagonist for treatment-experienced patients with HIV-1 infection. Expert Opin Investig Drugs, 2009, 18(11):1773-1785.
http://www.ncbi.nlm.nih.gov/pubmed/19888873