Evaluating of the clinical significance of drug interactions is one of the domains of clinical pharmacist expertise. Drug interactions are discussed when two or more drugs co-administer and the effect of one of them changes. Drug interactions can be a serious cause of toxicity and side effects. They can also lead to the failure of the treatment. On the other hand, they can also play a positive role, e. g. in the treatment of people living with HIV. The combination of some antiretrovirals with boosters is based on the principle of drug interaction. The article presents pharmacokinetic drug interactions of antiretrovirals. Their occurrence is not unique in the clinical practice. The pharmacokinetic profiles of the individual antiretrovirals, whose knowledge is essential for the correct assessment of the clinical significance of drug interactions, are reviewed.