Drug interactions
Phenoxybenzamine + Sildenafil
Severity: Major
Phenoxybenzamine and Sildenafil: major interaction.
Last updated Sources: US FDA label
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
Both drugs lower blood pressure, and combining them can cause symptomatic postural hypotension or syncope. The risk is greater with higher sildenafil doses.
What this interaction means in plain words
Phenoxybenzamine 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
Additive vasodilation from alpha-adrenergic blockade and PDE5 inhibition.
What to do
Use only when the patient is stable on the alpha blocker, start sildenafil at 25 mg, and separate doses by about 4 hours. Monitor blood pressure and counsel on orthostatic symptoms.
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 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 Phenoxybenzamine with Sildenafil?
MediHelp rates the interaction as major. Phenoxybenzamine 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. Both drugs lower blood pressure, and combining them can cause symptomatic postural hypotension or syncope. The risk is greater with higher sildenafil doses.
How serious is the interaction between Phenoxybenzamine 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 only when the patient is stable on the alpha blocker, start sildenafil at 25 mg, and separate doses by about 4 hours. Monitor blood pressure and counsel on orthostatic symptoms.
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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