Date of report 09 Mar 2020
Reported case interaction between
Cobicistat and Sildenafil
Cobicistat and Sildenafil
Drugs suspected to be involved in the DDI
Complete list of drugs taken by the patient
sildenafil
Clinical case description
57-year-old male diagnosed with HIV infection in 2013. Since then on successful antiretroviral treatment (previously treated with non-nucleoside analogues and protease inhibitors). Last HIV RNA pVL 20 copies/ml (September 2019). Within the last 2-3 years he had been taking sildenafil on demand and occasionally suffered from dizziness. In November 2019 he continued taking sildenafil 20 mg QD (self-prescribed) together with his current antiretroviral treatment DRV/c/FTC/TDF. He consulted because of severe headache, dizziness and a few episodes of syncope. After evaluation, he was advised to reduce sildenafil dose to a maximum of 20 mg every 48 hours. One month later the patient did not complain on any side effect of sildenafil.
Clinical Outcome
Drug Interaction Probability Scale (DIPS)
Editorial Comment
Based on theoretical considerations darunavir/cobicistat is expected to increase sildenafil plasma concentrations (CYP3A inhibition). Concomitant use of sildenafil for the treatment of erectile dysfunction with darunavir/cobicistat should be done with caution. If concomitant use of darunavir/cobicistat with sildenafil is indicated, sildenafil at a single dose not exceeding 25 mg in 48 hours is recommended. Rezolsta Summary of Product Characteristics, Janssen-Cilag Ltd, June 2018. This interaction is of great interest not only because of the clinical importance but also because it can be unnoticed in clinical practice, although it may be present in some groups of patients, such as those who practice Chemsex.
University of Liverpool Recommendation
Potential interaction - may require close monitoring, alteration of drug dosage or timing of administration