Background and importance The protease inhibitor (PI)/enhancer combination, more than 20 years after its appearance, continues to be the antiretroviral therapy (ART) of choice in certain circumstances due to its high genetic barrier. Ritonavir (RTV) acts as an enhancer and has a higher potential for drug interactions.
Aim and objectives To analyse the profile of pharmacological interactions with RTV as an enhancer of PIs and their severity.
Material and methods A retrospective observational study was conducted where patients undergoing treatment for HIV-1 infection with PI boosted with RTV before 2018 were reviewed. Patients who had been treated with RTV as an enhancer for at least 6 months were selected. Those that presented some interaction with PI/enhancer were reviewed. Data were collected on age, sex, drug interactions and their severity, and medical action/decision. The data were obtained from the drug dispensing register of the outpatient pharmaceutical care unit and the electronic clinical record. Interactions and their severity were reviewed using www.hiv-druginteractions.org/checker.
Results 210 patients were reviewed, of whom 5 patients (2.38%) had interactions that motivated treatment modification, reflected in the clinical history, with a mean age of 52 years (SD 5).
RTV–triazolam: avoid co–administration. RTV can increase triazolam concentrations resulting in prolonged sedation or respiratory depression. Decision: ART modification.
RTV–sildenafil: potential interaction. Co–administration of darunavir/RTV (400/100 mg twice daily) and a single dose of sildenafil resulted in fourfold greater exposure. Decision: use sildenafil single dose at a maximum 25 mg every 48 hours.
RTV–quetiapine: avoid co–administration. Concomitant administration of RTV and quetiapine is contraindicated because it can increase the toxicity related to quetiapine due to its metabolism mainly by CYP3A4, which RTV inhibits. Decision: reduce quetiapine dose to one–sixth if administered jointly.
RTV–atorvastatin: very low evidence interaction. Co–administration may increase atorvastatin concentrations and increase the risk of myopathy. Decision: exchange for pravastatin.
RTV–anti–VHC (ombitasvir+paritaprevir/RTV): avoid co–administration. Co–administration with additional ritonavir is not recommended. Optional decision: modification of ART until the end of anti–HCV treatment.
Conclusion and relevance Interactions related to ART based on PI/enhancer can be easily managed to avoid causing harm to the patient. It is necessary to review the complete treatment in ART patients whenever they start a new drug.
Conflict of interest No conflict of interest
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