Isentress (raltegravir), the first integrase inhibitor on the market for both treatment-naive and treatment-experienced patients, caused central nervous system (CNS) side effects in 10 percent of those taking the drug in an Italian study published in the journal AIDS. These problems included headaches, depression, anxiety, dizziness, insomnia and one case of altered dreams, among the group of 453 people studied. The culprits seemed to be tenofovir and also proton-pump inhibitors (such as Nexium or Prilosec), each of which can significantly increase blood levels of Isentress. The study’s authors recommend that before prescribing Isentress, health providers should carefully evaluate patients for psychiatric issues. Physicians should also monitor for CNS problems and take careful consideration of other drugs that may increase blood levels. In addition, they may even want to consider conducting therapeutic drug monitoring tests to check for those blood levels.