Sildenafil: uses, dosing, side effects & brands

REVATIO, phosphodiesterase-5 (PDE-5) inhibitor, is the citrate salt of sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type-5 (PDE-5). Sildenafil is also marketed as VIAGRA ® for erectile dysfunction.

The FDA classifies sildenafil as a phosphodiesterase 5 inhibitor. PDE5 inhibitors block the enzyme that breaks down cGMP, a signal that relaxes blood vessels. Letting cGMP build up widens vessels and boosts blood flow, which helps erectile dysfunction and eases pressure in the lung arteries. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.

The elimination half-life of sildenafil is about 4 hours — that is how long the body takes to clear half of a dose. Sildenafil's active N-desmethyl metabolite also has a terminal half-life of about 4 hours, so it is not materially longer. In older adults and in people with significant kidney or liver impairment, the label reports reduced drug clearance and higher blood levels (AUC/Cmax) of sildenafil — the label does not state the half-life itself is longer. Half-life is not the same as how long a drug test can detect the drug, and it varies with age, kidney and liver function.

It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run sildenafil against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.

We track 5 sildenafil-containing products in the U.S.: Revatio, Viagra, Vybrique, Liqrev and Sildenafil Citrate. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.

Across the brands we track, sildenafil is currently marketed as injectable, powder, tablet, film and suspension, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.

Yes. Our catalog lists 1 generic sildenafil product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.

The FDA's Enforcement database lists 2 recall records whose product description mentions sildenafil. The most recent: SILDENAFIL CITRATE USP (Aug 3, 2026). A recall applies to specific lots, not to the drug as a whole — check the record for the affected lot numbers.

Headache, facial flushing, indigestion or heartburn, stuffy nose, back and muscle aches, and vision changes such as a color tinge to vision or light sensitivity. All of them come from the same blood-vessel relaxation that produces the effect you want, so they tend to arrive with the peak effect and fade as the drug clears — sildenafil's half-life is about 4 hours. They are also dose-related: the label's adverse-event rates climb as you go from 25 mg to 50 mg to 100 mg. One practical detail from the label — a high-fat meal delays the peak by a mean of 60 minutes and lowers it by a mean of 29%, so if it seems slow or weak, take it on a lighter stomach.

Nitrates, in any form, at any time. That means nitroglycerin tablets, spray or patches, isosorbide mononitrate or dinitrate, and recreational "poppers" (amyl or butyl nitrite). The combination can drop blood pressure to a dangerous level, and it is a flat contraindication on the label. Riociguat, a guanylate cyclase stimulator, is also contraindicated. If you get chest pain after taking sildenafil, tell the paramedics and the ER exactly what you took and when: the label states it is unknown whether nitrates can be safely given even at 24 hours after a dose, so that timing changes how they treat you. Alpha-blockers for prostate or blood pressure (tamsulosin, doxazosin) can also cause fainting — the label says be stable on the alpha-blocker first, then start sildenafil at 25 mg.

An erection that persists longer than 4 hours, whether or not it is painful — the label says seek immediate medical assistance, because untreated priapism can cause penile tissue damage and permanent loss of potency. Do not wait it out overnight. Also emergency: sudden loss or dimming of vision in one or both eyes, which can be non-arteritic anterior ischemic optic neuropathy (NAION); sudden decrease or loss of hearing, sometimes with ringing or dizziness; and chest pain, severe dizziness or fainting during or after sex. For the vision and hearing events, the label's instruction is to stop the drug and seek prompt medical attention.

That depends on whether your heart can handle sex, not on the pill itself. The label states that in patients for whom sexual activity is not recommended because of their underlying cardiovascular status, ED treatments including sildenafil generally should not be used. Talk with your doctor first if you have unstable angina, had a heart attack or stroke in the last 6 months, have uncontrolled arrhythmias, low or poorly controlled blood pressure, or severe heart failure. Also flag it if you are on multiple blood pressure medicines — sildenafil lowers blood pressure modestly on its own, and stacking effects is what causes the dizziness and fainting.