Quinine and Ritonavir interaction
Quinine and Ritonavir: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Quinine (QUININE SULFATE) label · effective 2025-10-31
Therefore, the concomitant administration of ritonavir with quinine sulfate capsules should be avoided [see also DRUG INTERACTIONS ( 7.2 )] .
However, due to the significant effect of ritonavir on quinine pharmacokinetics, the concomitant administration of quinine sulfate capsules with ritonavir should be avoided [see also DRUG INTERACTIONS ( 7.1 )] .
Ritonavir In healthy subjects who received a single oral 600 mg dose of quinine sulfate with the 15 th dose of ritonavir (200 mg every 12 hours for 9 days), there were 4-fold increases in the mean quinine AUC and C max , and an increase in the mean elimination half-life (13.4 hours versus 11.2 hours), compared to when quinine was given alone.
Although a causal relationship between a specific drug and the arrhythmia was not established in this case, erythromycin is a CYP3A4 inhibitor and has been shown to increase quinine plasma levels when used concomitantly.
Antiepileptics (AEDs) (Carbamazepine, Phenobarbital, and Phenytoin) Carbamazepine, phenobarbital, and phenytoin are CYP3A4 inducers and may decrease quinine plasma concentrations if used concurrently with quinine sulfate.
From the Ritonavir (Norvir) label · effective 2026-07-23
Antiparasitic: quinine ↑ quinine A dose decrease of quinine may be needed when co-administered with ritonavir.
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.