Sildenafil has a half-life of about 4 hours, meaning half the drug is eliminated from your body every 4 hours after you take it. Most of the drug is cleared within 20 to 24 hours, though its noticeable effects typically fade well before that. The answer depends on whether you’re asking about how long the drug works, how long it’s detectable, or how long it takes to fully leave your system.
How Long the Effects Last
Sildenafil starts working about 30 minutes after you take it, with peak blood levels occurring around one hour. At that one-hour mark, a clinical study of men with erectile dysfunction found the average duration of firm erections was 26 minutes per session of arousal, compared to just 3 minutes with a placebo. But the drug doesn’t stop working after an hour or two.
That same study tested men at 8 and 12 hours after taking 100 mg. At 8 hours, 82% of men who responded at the one-hour mark were still responding. Even at 12 hours, 45% still showed a meaningful response, with self-reported erection duration averaging 16 minutes per arousal session. So while sildenafil is strongest in the first few hours, many men still feel its effects well into the following morning if they took it the night before.
How Long It Stays in Your Body
The standard rule for drug clearance is that it takes roughly five half-lives for a medication to be nearly eliminated. With sildenafil’s 4-hour half-life, that works out to about 20 hours for over 95% of the drug to be gone. Its active metabolite also has a 4-hour half-life, so it follows roughly the same timeline.
By 24 hours, blood levels are very low. The FDA notes, however, that even at 24 hours post-dose, it remains unclear whether certain medications (specifically nitrate drugs used for chest pain) can be safely combined with whatever trace amount remains. This is a relevant detail if you take heart medications, because the interaction between sildenafil and nitrates can cause a dangerous drop in blood pressure.
What Slows Clearance Down
Several factors can keep sildenafil in your system longer or change how strongly you feel it.
Food. Taking sildenafil with a high-fat meal delays its absorption by about an hour and reduces the peak concentration in your blood by 29%. This doesn’t necessarily make the drug stay longer overall, but it shifts the timing. You’ll wait longer to feel it kick in, and the peak effect will be somewhat weaker.
Age. Older adults tend to clear the drug more slowly. If you’re over 65, you can expect sildenafil to remain at higher levels in your blood for longer compared to someone in their 30s or 40s, even at the same dose.
Liver and kidney function. Sildenafil is processed primarily by the liver. If your liver or kidneys aren’t working at full capacity, the drug accumulates to higher levels and takes longer to clear. This is why lower starting doses are typically recommended for people with significant liver or kidney problems.
Other medications. Certain drugs slow down the liver enzyme responsible for breaking down sildenafil. Antifungal medications, some antibiotics, and HIV protease inhibitors are common examples. When these drugs are in your system, sildenafil’s effective duration can stretch noticeably, because the drug simply isn’t being metabolized as quickly.
Effects vs. Presence: Why the Difference Matters
There’s a practical gap between “still working” and “still in your system.” You’ll likely notice sildenafil’s effects for 4 to 6 hours, with diminishing but real benefits stretching to 8 or even 12 hours in some cases. But trace amounts of the drug linger in your bloodstream for closer to 24 hours.
For most people, this distinction is purely academic. Where it matters is drug interactions. If you need to take a nitrate medication for a heart condition, the relevant question isn’t “when will I stop noticing the effects?” but “when is the drug fully cleared?” And the honest answer from the FDA is that even at 24 hours, absolute safety with nitrates hasn’t been confirmed. If this applies to you, that conversation belongs with whoever prescribes your medications.
For anyone else simply wondering when their dose will wear off: plan on a solid 4 to 6 hours of noticeable effect, with a gradual taper after that. The drug will be essentially gone from your body by the following day.