Sildenafil with Nefazodone Interaction Details
Brand Names Associated with Sildenafil
- Revatio®
- Sildenafil
- Viagra®
Brand Names Associated with Nefazodone
- Nefazodone
- Serzone®
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 12, 2023
Interaction Effect
Increased sildenafil exposure
Interaction Summary
Sildenafil is metabolized by CYP3A4 enzymes, and nefazodone is a known inhibitor of CYP3A. Population pharmacokinetic analysis from patients in clinical trials demonstrated increased sildenafil exposure when coadministered with CYP3A inhibitors (for example, increased AUC by erythromycin (182%) and saquinavir (210%)). For erectile dysfunction, a reduced starting dose of sildenafil 25 mg should be used in patients also receiving nefazodone. Patients should also be monitored for an increase in sildenafil adverse effects. Concurrent use of CYP3A inhibitors is not recommended in patients being treated with sildenafil for pulmonary arterial hypertension .
Severity
Major
Onset
Unspecified
Evidence
Probable
How To Manage Interaction
Nefazodone may increase the bioavailability of sildenafil. The concurrent use of nefazodone and sildenafil is not recommended in patients treated for pulmonary arterial hypertension. For erectile dysfunction, use sildenafil with caution at a reduced starting dose of 25 mg in patients also receiving nefazodone .
Mechanism Of Interaction
Inhibition of CYP3A4-mediated metabolism of sildenafil
Literature Reports
A) In clinical studies, sildenafil Cmax was increased 140% and sildenafil AUC increased 210% when administered with saquinavir, a strong CYP3A4 inhibitor .
B) In clinical studies, sildenafil Cmax was increased 160% and sildenafil AUC increased 182% when administered with erythromycin, a moderate CYP3A4 inhibitor .
Sildenafil Overview
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Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Revatio) is used to improve the ability to exercise in adults and children 1 year of age and older with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the lungs, causing shortness of breath, dizziness, and tiredness). Sildenafil is in a class of medications called phosphodiesterase (PDE) inhibitors. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. This increased blood flow can cause an erection. Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily.
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If you are taking sildenafil to treat erectile dysfunction, you should know that it does not cure erectile dysfunction or increase sexual desire. Sildenafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus (HIV).
Nefazodone Overview
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Nefazodone is used to treat depression. Nefazodone is in a class of medications called serotonin modulators. It works by increasing the amounts of certain natural substances in the brain that are needed to maintain mental balance.
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Definitions
Severity Categories
Contraindicated
These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.
Major
This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.
Moderate
This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.
Minor
While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.
Onset
Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.
Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.
Evidence
Level of documentation of the interaction.
Established: The interaction is documented and substantiated in peer-reviewed medical literature.
Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.
How To Manage The Interaction
Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.
It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.
Mechanism Of Interaction
The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.
Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.
Where Does Our Information Come From?
Information for our drug interactions is compiled from several drug compendia, including:
The prescribing information for each drug, as published on DailyMED, is also used.
Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.
The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.