Approximately 10% of patients taking the antiretroviral drug raltegravir (Isentress), an Integrase Inhibitor,  develop central nervous system (CNS) side-effects. The development of CNS side-effects was associated with the co-administration of tenofovir (Viread, also found in the co-formulations TruvadaAtripla and Eviplera) and of proton pump inhibitors (drugs used to reduce gastric acid). The investigators believe these drugs interact with raltegravir, increasing its plasma concentrations, and so potentially leading to CNS symptoms.

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