What Medications Should Not Be Taken With Viagra or Sildenafil?
Sildenafil must never be combined with nitrates, and several other drugs, grapefruit and alcohol can interact too — which is why disclosing everything you take matters.
The single most important rule with Viagra is that sildenafil must never be combined with nitrate medicines, because together they can cause a sudden and dangerous drop in blood pressure. Several other drugs and substances also interact with sildenafil, which is why telling your doctor about everything you take — prescriptions, over-the-counter products and supplements — is not a formality but a safety step.
The dangerous interaction: nitrates
Nitrates are medicines used to relieve chest pain (angina) and treat some heart conditions. Common examples include nitroglycerin, isosorbide dinitrate and isosorbide mononitrate. Both nitrates and Viagra widen blood vessels and lower blood pressure; taken together the effect compounds and can drop blood pressure to a life-threatening level. This is an absolute contraindication — there is no safe gap or smaller dose that makes the combination acceptable. If you take any nitrate, you cannot take Viagra, and this also applies to recreational "poppers" (amyl nitrite).
Other medications that interact with sildenafil
Beyond nitrates, several prescription drugs should be avoided or used only under close medical supervision with Viagra:
- Riociguat (Adempas) and vericiguat — used for pulmonary hypertension and heart failure; should not be combined with sildenafil.
- Alpha-blockers — prescribed for blood pressure or an enlarged prostate; can add to sildenafil's blood-pressure-lowering effect.
- Some blood-pressure medicines — may need dose timing adjusted by a doctor.
- Mifepristone, lefamulin and voxelotor — may interact and are generally best avoided with Viagra.
- Certain antifungals and antibiotics — can raise sildenafil levels in the blood, increasing side effects.
This is not a complete list, which is exactly why a pharmacist's check is valuable. Specific situations such as Viagra with finasteride or Propecia and Xarelto with Viagra or Cialis have their own guides.
Over-the-counter products, grapefruit and alcohol
Some non-prescription items matter too. Grapefruit and grapefruit juice can increase the amount of sildenafil in your bloodstream, raising the risk of side effects. Drinking heavily alongside Viagra adds to blood-vessel dilation and can worsen dizziness or low blood pressure, as well as making an erection harder to achieve. Herbal supplements marketed for "performance" can contain undisclosed ingredients — including unlabelled sildenafil itself — so they should be treated with caution and disclosed to your doctor.
Why "no known interaction" still needs a check
It helps to understand why these warnings exist. Sildenafil widens blood vessels and is broken down in the liver by specific enzymes, so two kinds of problem can arise: other drugs that also lower blood pressure can stack with it, and drugs that slow its breakdown can leave too much sildenafil in the blood, amplifying side effects. That is why even medicines without a headline "do not combine" label can still matter — the safe dose may simply be different. A pharmacist can run your full list against sildenafil in moments, which is far quicker than guessing and removes the risk of an overlooked combination.
How to stay safe
Before starting Viagra, give your doctor or pharmacist a full list of everything you take, and never share or borrow ED medication, since you do not know what the other person has been prescribed. If you have heart disease or take blood-pressure drugs, read taking Viagra with a heart condition as well. Used within these limits, sildenafil is a well-understood and safe medicine for most men.
For the full set of safety and interaction guides, return to our erectile dysfunction and Viagra hub.