Drug interactions
Primidone + Tadalafil
Severity: Moderate
Primidone and Tadalafil: moderate 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
Primidone is metabolised to phenobarbital, which induces CYP3A4 and can reduce tadalafil exposure. Loss of efficacy may occur, especially in pulmonary hypertension.
What this interaction means in plain words
Primidone and Tadalafil can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Primidone belongs to Central Nervous System; Tadalafil belongs to Genitourinary.
Why it happens
Primidone and its metabolite phenobarbital induce CYP3A4, increasing tadalafil metabolism.
What to do
Avoid the combination in pulmonary arterial hypertension. In erectile dysfunction, monitor response and adjust the tadalafil dose if needed.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Tadalafil
- Amyl nitrite + Tadalafil Contraindicated
- Isosorbide dinitrate + Tadalafil Contraindicated
- Isosorbide mononitrate + Tadalafil Contraindicated
- Nitroglycerin po + Tadalafil Contraindicated
- Nitroglycerin rectal + Tadalafil Contraindicated
- Nitroglycerin sublingual + Tadalafil Contraindicated
Other interactions of Primidone
- Lorlatinib + Primidone Contraindicated
- Lurasidone + Primidone Contraindicated
- Primidone + Ranolazine Contraindicated
- Primidone + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
- Primidone + Voriconazole Contraindicated
- Abiraterone + Primidone Major
Frequently asked questions
Can I take Primidone with Tadalafil?
MediHelp rates the interaction as moderate. Primidone and Tadalafil can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Primidone is metabolised to phenobarbital, which induces CYP3A4 and can reduce tadalafil exposure. Loss of efficacy may occur, especially in pulmonary hypertension.
How serious is the interaction between Primidone and Tadalafil?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination in pulmonary arterial hypertension. In erectile dysfunction, monitor response and adjust the tadalafil dose if needed.
What other medicines interact with Tadalafil?
MediHelp also lists interactions of Tadalafil with, for example, Amyl nitrite, Isosorbide dinitrate, Isosorbide mononitrate. The full list is on the Tadalafil page.
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