Drug-drug interactions in the treatment of HIV infection: focus on pharmacokinetic enhancement through CYP3A inhibition.

The aim of this review is to discuss the effect of pharmacokinetic drug-drug interactions (DDIs) in the antiretroviral treatment of HIV infection. In particular, but not exclusively, DDIs due to the cytochrome P450 3A (CYP3A) inhibitor ritonavir, which is used to increase antiretroviral drug exposure - a technique known as pharmacokinetic enhancement or 'ritonavir boosting'- will be reviewed. The emphasis here will be on the treatment of important co-morbidities common in patients with HIV, including dyslipidaemia, hypertension, tuberculosis and opiate dependence, as well as on the potentially life-threatening interaction between ritonavir and inhalational steroids, and on the effect of acid-reducing agents on some antiretroviral drugs. Finally, further developments with regard to the use of CYP3A-blocking agents to augment the efficacy of antiviral therapy will be discussed.