Drug interactions
Saquinavir + Sildenafil
Severity: Major
Saquinavir and Sildenafil: major interaction.
Last updated
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
Saquinavir inhibits CYP3A4 and substantially raises sildenafil concentrations. This increases the risk of hypotension, visual disturbances, syncope and prolonged erection or priapism.
What this interaction means in plain words
Saquinavir and Sildenafil 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.
Why it happens
Saquinavir inhibits CYP3A4-mediated metabolism of sildenafil, reducing its clearance.
What to do
Use a reduced starting sildenafil dose for erectile dysfunction (for example 25 mg, not repeated within 48 hours) and monitor blood pressure. For pulmonary arterial hypertension, avoid the combination or follow labeling for strong CYP3A4 inhibitors.
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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Other interactions of Sildenafil
- Amyl nitrite + Sildenafil Contraindicated
- Atazanavir + Sildenafil Contraindicated
- Cobicistat + Sildenafil Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Sildenafil Contraindicated
- Glyceryl trinitrate pr + Sildenafil Contraindicated
- Isosorbide dinitrate + Sildenafil Contraindicated
Frequently asked questions
Can I take Saquinavir with Sildenafil?
MediHelp rates the interaction as major. Saquinavir and Sildenafil 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. Saquinavir inhibits CYP3A4 and substantially raises sildenafil concentrations. This increases the risk of hypotension, visual disturbances, syncope and prolonged erection or priapism.
How serious is the interaction between Saquinavir and Sildenafil?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use a reduced starting sildenafil dose for erectile dysfunction (for example 25 mg, not repeated within 48 hours) and monitor blood pressure. For pulmonary arterial hypertension, avoid the combination or follow labeling for strong CYP3A4 inhibitors.
What other medicines interact with Sildenafil?
MediHelp also lists interactions of Sildenafil with, for example, Amyl nitrite, Atazanavir, Cobicistat. The full list is on the Sildenafil page.
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