Maraviroc

It is the second entry inhibitor. Because it is well absorbed orally, it is formulated as an oral tablet. Maraviroc blocks the CCR5 co-receptor that works together with gp41 to facilitate HIV entry through the membrane into the cell. HIV may express preference for either the CCR5 co-receptor or the CXCR4 co-receptor or both. A test to determine viral tropism is required to distinguish the virus's use of the CCR5 from the CXCR4 co-receptor as well as mixed and dual tropic virus. Only the R5 virus that uses CCR5 to gain access to the cell can be treated with maraviroc. Maraviroc is metabolized by CYP450 liver enzymes, and the dose must be reduced when given with most protease inhibitors and increased in patients receiving the NNRTIs efavirenz, and etravirine. Maraviroc is generally well tolerated.HIV-1 infection begins with attachment of an HIV envelope protein called gp120 to CD4 molecules on surfaces of helper T cells and other antigen-presenting cells such as macrophages and dendritic cells.Although resistance has occurred, there is minimal cross-resistance with other antiretroviral drugs. Maraviroc is used orally and has good tissue penetration. It is a substrate for CYP3A4, and dosage adjustments may be needed in the presence of drugs that induce or inhibit this enzyme. Adverse effects of maraviroc include cough, diarrhea, muscle and joint pain, and increases in hepatic transaminases.