How Long Do ED Pills Stay in Your System? Half-Life Table

The table below puts all four FDA labels side by side. We read each label on DailyMed on 14 November 2026.

ED pill half-life table

Half-lives and peak times are quoted from the labels: Viagra, Cialis, vardenafil and Stendra, read 14 November 2026. The last column is our arithmetic, explained below. It is not a label figure.

What a half-life means

A half-life is the time it takes for the level of a drug in your blood to fall by half. After one half-life, half is left. After two, a quarter. After five, about 3% is left, since half of half of half, five times over, is one part in 32. That is our arithmetic, not a label claim, and the last column of the table uses it.

These are averages from healthy men in the label studies. Age, liver and kidney health, and other medicines can change them. The labels say so, and some drugs slow the clearing a lot, as the sections below show.

How long does Viagra stay in your system?

The Viagra label says: "Both sildenafil and the metabolite have terminal half lives of about 4 hours" (DailyMed: Viagra label, read 14 November 2026). The "metabolite" is what the body turns sildenafil into, and it works in a similar way.

The label also gives a direct number for the next day: "plasma levels of sildenafil at 24 hours post dose are approximately 2 ng/mL (compared to peak plasma levels of approximately 440 ng/mL)" (Viagra label). In plain words, a day later less than 1% of the peak level is left in a healthy man. In men over 65 or with liver or kidney problems, the label says the 24-hour level is higher.

Sildenafil half-life and peak time

Sildenafil peaks fast. The label says: "Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state" (Viagra label). A heavy, fatty meal slows that down. Generic sildenafil is the same drug, so the same numbers apply. The FDA says bioequivalence "generally means the generic drug delivers the same amount of active ingredient to a patient at the same rate and to the same extent as the brand name drug." (FDA: generic drugs questions and answers, read 14 November 2026). Generic sildenafil starts at $1.60 a dose online at Strut Health.

How long does Cialis stay in your system?

Much longer than the others. The Cialis label says: "the mean terminal half-life is 17.5 hours in healthy subjects" (DailyMed: Cialis label, read 14 November 2026). Using the five half-lives rule, that is about three and a half days before roughly 3% is left, by our arithmetic.

Tadalafil half-life and peak time

Tadalafil takes longer to peak, and food does not change it. The label says the peak level "is achieved between 30 minutes and 6 hours (median time of 2 hours)" and that "The rate and extent of absorption of tadalafil are not influenced by food" (Cialis label). The long half-life is why tadalafil is the one ED pill also sold for daily use. Generic tadalafil starts at $1.80 a dose at Rex MD. Our daily tadalafil cost guide compares daily and as-needed plans.

Vardenafil half-life

The generic vardenafil label says: "the terminal half-life of vardenafil and its primary metabolite (M1) is approximately 4-5 hours" (DailyMed: vardenafil label, read 14 November 2026). Peak levels are "usually reached between 30 minutes and 2 hours (median 60 minutes)". Some medicines stretch that a lot: the label says ritonavir, an HIV drug, "significantly prolonged the half-life of vardenafil to 26 hours". Our vardenafil vs sildenafil guide compares the two.

Avanafil (Stendra) half-life

Stendra peaks fastest of the four. Its label gives "a median T max of 30 to 45 minutes in the fasted state", where T max means the time to peak, and says "STENDRA has a terminal elimination half-life of approximately 5 hours" (DailyMed: Stendra label, read 14 November 2026). Our Stendra cost guide covers who sells it.

Why this matters: nitrates

Half-life matters most if you ever need a nitrate, a chest pain medicine. Nitrates must never be taken with an ED pill, because together they can drop blood pressure to a dangerous level. MedlinePlus explains: "Nitrates come as tablets, sublingual (under the tongue) tablets, sprays, patches, pastes, and ointments." (MedlinePlus: tadalafil, read 14 November 2026).

The labels set waiting times for an emergency. The Cialis label says "at least 48 hours should have elapsed after the last dose of CIALIS before nitrate administration is considered" (Cialis label). The Stendra label says "at least 12 hours should elapse after the last dose of STENDRA" (Stendra label). The Viagra label says "it is unknown whether nitrates can be safely co-administered" even at 24 hours (Viagra label). If you go to an emergency room with chest pain, tell the staff which ED pill you took and when.

Half-life is not how long the effect lasts

A drug can still be in your blood after its effect is gone, or the effect can fade before the drug is cleared. How long each pill helps with an erection is a separate question from how long it stays in your system. The labels measure blood levels, not erections. Our guides on how long Viagra lasts and how long Cialis lasts cover the effect.