Drug interactions
Loperamide + Ritonavir
Severity: Major
Loperamide and Ritonavir: major interaction.
Last updated Sources: UK SmPC
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Ritonavir strongly inhibits CYP3A4 and P-glycoprotein, increasing loperamide exposure. This raises the risk of CNS opioid effects and QT prolongation or torsades de pointes, especially with higher loperamide doses.
What this interaction means in plain words
Loperamide and Ritonavir can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Loperamide belongs to Gastrointestinal Tract; Ritonavir belongs to Anti Virals.
Why it happens
Inhibition of CYP3A4 metabolism and P-gp efflux of loperamide.
What to do
Avoid high or prolonged loperamide dosing; if needed use the lowest dose briefly and monitor for sedation and cardiac symptoms, with ECG if risk factors exist.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Loperamide
Other interactions of Ritonavir
- Alfuzosin + Ritonavir Contraindicated
- Amiodarone + Ritonavir Contraindicated
- Avanafil + Ritonavir Contraindicated
- Colchicine + Ritonavir Contraindicated
- Dronedarone + Ritonavir Contraindicated
- Eletriptan + Ritonavir Contraindicated
Frequently asked questions
Can I take Loperamide with Ritonavir?
MediHelp rates the interaction as major. Loperamide and Ritonavir can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Ritonavir strongly inhibits CYP3A4 and P-glycoprotein, increasing loperamide exposure. This raises the risk of CNS opioid effects and QT prolongation or torsades de pointes, especially with higher loperamide doses.
How serious is the interaction between Loperamide and Ritonavir?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid high or prolonged loperamide dosing; if needed use the lowest dose briefly and monitor for sedation and cardiac symptoms, with ECG if risk factors exist.
What other medicines interact with Loperamide?
MediHelp also lists interactions of Loperamide with, for example, Amiodarone, Amisulpride, Anagrelide. The full list is on the Loperamide page.
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