Date of report 26 Nov 2019
Reported case interaction between
 Ritonavir and Solifenacin

FLS Science

Drugs suspected to be involved in the DDI

Perpetrator
Ritonavir
Daily Dose
200 (mg)
Dose adjustment performed
No
Administration Route
Oral
Start date
Jan. 1, 2010
End date
Ongoing
Victim
Solifenacin
Daily Dose
5 (mg)
Dose adjustment performed
No
Administration Route
Oral
Start date
Oct. 24, 2019
End date
Nov. 4, 2019

Complete list of drugs taken by the patient

Antiretroviral treatment
Darunavir (with Ritonavir or Cobicistat)
Ritonavir
Etravirine
Raltegravir
Complete list of all comedications taken by the patient, included that involved in the DDI

Aciclovir, atorvastatin 10mg QD, Fenofibrate 145 mg QD, ramipril/Hydrochlorothiazide 5/25 mg QD, amlodipine 5mg QD, solifenacin 5 mg QD

Clinical case description

Gender
Male
Age
69
eGFR (mL/min)
>60
Liver function impairment
No
Description

69 year-old male with HIV infection on treatment with darunavir/ritonavir + etravirine + raltegravir (multi-experienced, multi-resistant) since 2010. Prescribed with solifenacin 5 mg QD due to prostatic syndrome since 24/Oct/2019. The patient complains about dry mouth since he started taking solifenacin. On 4/Nov/2019 solifenacin was replaced by tamsulosin 0.4 mg QD, with resolution of symptoms.

Clinical Outcome

Toxicity

Drug Interaction Probability Scale (DIPS)

Score
5 - Probable

Editorial Comment

Solifenacin is metabolized by CYP3A4 and concentrations are likely to increase due to inhibition of CYP3A4 by ritonavir. It is recommended that solifenacin dosage should be limited to 5 mg once daily if coadministered with a strong CYP3A4 inhibitor such as ritonavir. Even so, close monitoring for adverse events (as in this patient) is recommended.

University of Liverpool Recommendation

Potential interaction - may require close monitoring, alteration of drug dosage or timing of administration
For more information click here