Date of report 22 Jun 2020
Reported case interaction between
Ritonavir and Quetiapine
Ritonavir and Quetiapine
Drugs suspected to be involved in the DDI-summary
Complete list of drugs taken by the patient
Lormetazepam 1mg/day, Mirtazapine 30mg/12h, Clonazepam 0.5mg 2 tablets/day, Venlafaxine retard 300mg/day, Quetiapine 300mg/day, Quetiapine 200mg/day
Clinical case description
HIV- infected patient who started treatment with quetiapine 500mg after hospital admission due to major depression and psychotic episode, while he was receiving TDF/FTC + Darunavir/ritonavir 800/100 mg QD for his HIV infection at that moment. Psychiatric treatment was adjusted several times due to decompensation, but the quetiapine dose was never changed. The patient remains stable from a psychiatric point of view, and boosted-PI has been maintained not to alter quetiapine levels. In 2016, ritonavir was changed to cobicistat without consequences. Finally, in 2019 the regimen was switched to TAF/FTC/DRV/cobi. Several ECG have been performed to monitor the QT interval, and they have always been within normal range.
Clinical Outcome
Editorial Comment
It is important to note that in the European SPC both ritonavir and cobicistat-containing regimens are contraindicated with quetiapine due to the known inhibition of CYP3A4 metabolism and therefore potential increase in quetiapine exposure. In the US prescribing information the recommendation is to dose reduce the quetiapine to 1/6th of the dose. Individualization of dosing to manage a drug interaction is an important principle of patient management. Despite this particular case, it is important to be very cautious about this interaction. Note that quetiapine can be administered over a range of doses and the greatest concern will be at higher doses when the implications of increasing the exposure is greatest.
University of Liverpool Recommendation
These drugs should not be coadministered