Sildenafil Drug Interactions: What You Need to Know

Sildenafil, the active ingredient in Viagra and generic sildenafil tablets, is generally well tolerated by many men with erectile dysfunction, but sildenafil interactions can still be serious: some medicines must never be combined, including nitrates and riociguat, because they can cause a potentially dangerous drop in blood pressure, while others such as blood pressure tablets and antibiotics like clarithromycin may need extra caution because they can increase side effects or raise sildenafil levels.

For adults in the UK who use or are considering sildenafil especially if you also take other medicines, supplements or drink alcohol this guide sets out what genuinely needs to be avoided, what usually just needs a prescriber's awareness, and how to use the quick-reference table to check common combinations.

This is general information, not personal medical advice. Always tell your prescriber and pharmacist about every medicine, supplement and recreational substance you use, so they can check your specific combination. Treatment suitability depends on an individual clinical assessment.

Medicines You Must Never Combine With Sildenafil

This is the one category where the guidance is a firm avoidance, not just caution. Nitrate medicines, including glyceryl trinitrate (GTN) spray, isosorbide mononitrate and isosorbide dinitrate, used for angina and chest pain, must never be taken with sildenafil. Nicorandil, another angina medicine, and riociguat, a guanylate cyclase stimulator used for pulmonary hypertension, carry the same risk. Sildenafil should not be used with guanylate cyclase stimulators such as riociguat. This advice applies to anyone taking nitrate medicines. All of these act through the nitric oxide pathway to relax blood vessels, and combined with sildenafil this can cause a severe, dangerous drop in blood pressure.

Recreational drugs known as poppers, amyl nitrite and butyl nitrite, work the same way as prescription nitrates and carry the same danger when combined with sildenafil. Telling your prescriber about any recreational substance use is important for safe prescribing.

Blood Pressure Medicines: Caution, Not a Ban

Sildenafil itself has a mild blood pressure-lowering effect, so combining it with a blood pressure medicine can add to that effect.

This is a real consideration, but for most blood pressure medicines it means individual assessment and possibly a more cautious starting dose, not an outright ban, the exception is nitrate medicines, which should not be used with sildenafil because of the risk of a significant drop in blood pressure.

Alpha-blockers, such as tamsulosin, doxazosin, alfuzosin and terazosin, carry a more specific and better-documented risk of symptomatic low blood pressure, particularly when standing up, so these often warrant closer attention and a cautious starting approach.

Can You Take Viagra With Entresto?

This combination needs caution rather than avoidance. Entresto (sacubitril/valsartan), used for heart failure, lowers blood pressure, and studies suggest that adding sildenafil may cause a small additional reduction in blood pressure on top of Entresto's own effect.

There is no known clinically significant effect on how the two medicines are processed by the body, the effect is simply additive blood pressure lowering. This is exactly the kind of combination a prescriber needs to know about and factor into an individual assessment, particularly given that heart failure is a condition that requires careful assessment before sildenafil is prescribed.

Can I Take Sildenafil With Ramipril or Other Blood Pressure Tablets?

Ramipril, an ACE inhibitor, and similar blood pressure drugs are not specifically named as a contraindication with sildenafil, but the same general principle applies: sildenafil can add to their blood pressure-lowering effect. Calcium channel blockers such as amlodipine, commonly used to treat high blood pressure, follow the same pattern, with trial data showing an additive supine blood pressure reduction of around 8 mmHg systolic and 7 mmHg diastolic when combined with sildenafil, rather than a large change in how much sildenafil is in the bloodstream.

Beta-blockers do not have a well-established clinically significant direct interaction with sildenafil, although the underlying heart condition still needs assessment.

In all these cases, your prescriber weighs up your specific high blood pressure control and overall health before confirming sildenafil is appropriate, and while a common starting dose is 50mg, combinations affecting blood pressure may lead them to choose a lower starting dose instead.

Medicines That Can Raise Sildenafil Levels

Sildenafil citrate is broken down in the body mainly by a liver enzyme called CYP3A4. Medicines that inhibit this enzyme can increase sildenafil levels in the body, increasing the chance of adverse effects. Clarithromycin, a commonly prescribed antibiotic, is a genuine example of this.

Studies suggest it can significantly increase sildenafil levels in the blood, which is why your prescriber may recommend a lower starting dose if you need both. Erythromycin works similarly.

Some antifungal medicines can substantially increase sildenafil exposure. Antifungal drugs such as ketoconazole and itraconazole, along with the antiviral medicines ritonavir and saquinavir, typically call for a reduced sildenafil dose if combined to help lower the risk of serious side effects, especially if you also take other medications.

Grapefruit juice can increase sildenafil exposure, although the effect is generally modest. This is unlikely to be significant for most people, but it is worth being aware of if you notice stronger effects or side effects after drinking grapefruit juice.

Medicines That Can Reduce Sildenafil's Effect

Bosentan, used for pulmonary hypertension, works in the opposite direction, speeding up how quickly sildenafil is cleared from the body and potentially reducing its effect. This combination is mainly relevant to people being treated for pulmonary hypertension rather than typical erectile dysfunction use, but it is worth your prescriber knowing about if it applies to you.

Can You Take Sildenafil With Atorvastatin?

Yes. There is no well-established clinically significant direct interaction between atorvastatin and sildenafil.

Does L-Tyrosine Interact With Sildenafil or Omeprazole?

No well-established clinically significant interaction is known between L-tyrosine and sildenafil or omeprazole. Because supplement safety data can be limited, tell your prescriber or pharmacist about any supplements you take.

Sildenafil and Alcohol

Both alcohol and sildenafil can lower blood pressure, so combining them has the potential to add to that effect, and alcohol itself can also make it harder to get or keep an erection, working against what sildenafil is meant to help with. Alcohol may also increase the likelihood of side effects such as dizziness, especially with heavier drinking. There is no officially stated "safe number of units" for combining alcohol with sildenafil.

Moderate alcohol consumption has not consistently been shown to cause a clinically significant additional fall in blood pressure with sildenafil, but heavier drinking can increase dizziness and other side effects.

Can You Take Sildenafil While on Antibiotics?

It depends on which antibiotic. Most antibiotics have no significant interaction with sildenafil. The exceptions worth knowing are clarithromycin and erythromycin, which can meaningfully raise sildenafil levels, as covered above. If you are prescribed a course of antibiotics while using sildenafil, mentioning both to your pharmacist is a sensible check, particularly if the antibiotic is one of these two.

How Long Does Sildenafil Stay in Your System and How Long Does It Last?

The effects of sildenafil may last for up to around 4 hours, although the effect may gradually reduce over time as levels in the blood fall, lifestyle factors like high-fat meals may delay absorption and slow onset even though the medicine still remains active for several hours, which can affect how sildenafil works when you are taking sildenafil to support your sex life by improving blood flow to the penis.

Sildenafil has a terminal half-life of about 4 hours.

The medicine is therefore largely eliminated within roughly a day, although clearance can vary with age, liver function and other individual factors.

What Is the Maximum Recommended Dose of Sildenafil?

The maximum recommended dose and frequency will depend on individual circumstances and should always follow prescriber advice and product guidance. This is always a decision made by your prescriber based on an individual clinical assessment, not something to work out from a general article.

Factors such as your health conditions, other medicines, and how you respond to treatment all influence the appropriate dose and any interaction-related adjustments. Never adjust your own dose based on something you have read, including this guide.

Quick Reference: Sildenafil Interaction Summary

This table summarises general information and is not exhaustive. Always check your specific combination with a pharmacist or prescriber.

Medical Disclaimer

This guide is for general information only and does not constitute medical advice. It is not a substitute for a consultation with a qualified healthcare professional. Treatment suitability depends on an individual clinical assessment. Sildenafil should only be used following assessment by an appropriately qualified healthcare professional, who will determine whether sildenafil and your other medicines can be used together safely. Results vary between individuals. If you experience symptoms such as severe dizziness, fainting, chest pain or any other concerning symptoms, seek medical attention promptly or contact NHS 111.