When you take sildenafil, commonly known as Viagra, you might ask: How long will it work once you take it? Will it last long enough? Or will it fade too soon? Uncertainty can be frustrating, especially when timing matters.
Sildenafil is fast-acting and lasts for hours. Most people feel its effects in about 30 minutes, with peak performance around one hour. But the duration isn’t the same for everyone. Age, metabolism, food, and even medications can affect how long it stays active.
In this article, you will learn exactly how long sildenafil lasts, what affects its effectiveness, and how to get the best results. Whether you’re new to it or looking to optimize its effects, this guide has you covered.
| 🔑 Key Takeaways ➤ Sildenafil starts working within 30 minutes for most people, with peak effects around one hour after taking it. ➤ The drug remains effective for about four hours, though its strength gradually declines after two hours. ➤ Age affects how long sildenafil stays in the body, with older men experiencing longer-lasting effects due to slower clearance. ➤ Liver and kidney function impact how quickly sildenafil is removed, which can lead to stronger or prolonged effects in people with impairments. ➤ Taking sildenafil with a high-fat meal can delay its onset by about an hour and slightly reduce its peak effect. ➤ Certain medications, especially those that inhibit liver enzymes, can increase sildenafil levels and extend its duration. ➤ Compared to other ED medications, sildenafil has a moderate duration, while tadalafil lasts much longer and avanafil works faster. ➤ For best results, take sildenafil on an empty stomach about one hour before sexual activity, avoiding heavy meals that can slow absorption. |
General Duration Timeline
Below we’ll review how long Sildenafil takes to start working, when its effects are strongest, and how long it stays in your system.
Onset of Action
Sildenafil works quickly. In one study, patients took a 50‐mg dose and reached an erection within a median time of 27 minutes. In this study, some men noticed an effect as soon as 12 minutes after taking the pill, while others took as long as 70 minutes.
Most patients (about 71%) experienced a firm erection within 30 minutes.
Peak Effect
The drug is absorbed fast. According to the FDA’s product label (VIAGRA®), maximum plasma levels are reached between 30 and 120 minutes after a dose, with a median around 60 minutes. This means that most patients will feel its strongest effect within an hour after taking it.
Duration of Action
The overall effect of sildenafil lasts for about 4 hours. Data from the same study show that when visual sexual stimulation began 2 hours after dosing, the median duration of a firm erection was about 19.5 minutes.
If stimulation started 4 hours after taking the pill, the median duration dropped to around 5 minutes. Although the response is strongest in the middle of that window, the drug still helps produce an erection for up to 4 hours.
Half-Life and Clearance
Sildenafil has a half-life of roughly 3 to 4 hours. This means that every 3 to 4 hours, the drug’s concentration in the blood is cut by half. This short half-life supports its as-needed use, as the body clears the drug fairly quickly and it does not build up over time.
| ❓ What This Means for You If you take a typical 50-mg dose, you might start noticing its effects in about 30 minutes, with the strongest effects around one hour later. Even though the peak effect diminishes after about 2 hours, you can expect some benefit for up to 4 hours. |
Factors Affecting Duration
Below are several factors that can change how long sildenafil works in your body. These factors affect the drug’s clearance (how quickly it is removed) and its half‐life (the time it takes for half of the drug to be cleared). Let’s look at these factors in more detail.
Age and Its Effect on Duration
Studies have shown that age makes a difference. In one study, young men (average age 30) had a sildenafil half‐life of about 2.6 hours, while elderly men (average age 70) had a half‐life of about 3.8 hours. This means that in older men, the drug stays in the blood longer.
In addition, although total plasma levels increased by 60–70% in elderly subjects, the free (active) drug levels were only about 40% higher because of stronger protein binding in older people.
This change may extend the duration of action in older men and is why a lower starting dose (25 mg) is recommended for those over 65.
Renal Function and Duration
Kidney (renal) health can also affect how long sildenafil lasts. In a study comparing men with normal renal function to those with severe renal impairment (creatinine clearance less than 30 mL/min), researchers found that subjects with poor kidney function had almost double the exposure (AUC) and higher maximum levels (Cmax) of sildenafil.
Although the half-life did not change dramatically (for example, about 3.4 hours in normal subjects compared to 3.9 hours in those with severe impairment), the increased levels mean that the drug may have a longer or stronger effect.
This is important when deciding on a safe starting dose for patients with kidney problems.
Hepatic (Liver) Impairment and Duration
The liver is the main organ that clears sildenafil from the body. In patients with liver problems, such as chronic stable cirrhosis, the clearance is reduced.
In one study, men with normal liver function had an average half-life of about 3.2 hours, while those with hepatic impairment had a half-life of about 4.3 hours. In this case, the AUC (a total exposure measure) increased by nearly 85%, and Cmax was about 47% higher in the liver-impaired group.
This shows that liver disease slows down the removal of sildenafil, potentially extending its duration of action. Because of these changes, a lower starting dose is often recommended for patients with liver issues.
Food Effects on Duration
Taking sildenafil with food—especially a high-fat meal—also changes how the drug works. When taken after a high-fat meal, the time to reach the maximum level is delayed by about 60 minutes, and the peak concentration (Cmax) is reduced by roughly 29%, according to the VIAGRA® label by the FDA.
Although the total exposure (AUC) is only slightly reduced (by about 11%), the slower absorption may delay the onset of action and subtly affect the duration of effect.
Drug Interactions That May Affect Duration
Sildenafil is mainly cleared by enzymes in the liver (especially CYP3A4). When strong inhibitors like ketoconazole or ritonavir are taken at the same time, sildenafil’s levels can increase dramatically—sometimes by as much as 11-fold.
This increase not only boosts the effect but may also prolong the time the drug stays in the body. Such interactions are why doctors advise careful dosing when other medications are involved.
Comparison with Other ED Medications
| PDE5 Inhibitor | Onset of Action | Half-Life | Effective Duration | Food Sensitivity |
| Sildenafil (Viagra®) | 30–60 minutes* | Approximately 4 hours | Approximately 4–6 hours | High-fat meals can delay onset by ~60 minutes and reduce Cmax by ~29% |
| Vardenafil (Levitra®) | ~30 minutes | 4–6 hours | Approximately 4–5 hours | Less affected by food compared to sildenafil |
| Tadalafil (Cialis®) | 30 minutes to 1 hour | Approximately 17.5 hours | Up to 24–36 hours | Largely unaffected by food |
| Avanafil | As fast as 10 minutes | Not specified precisely; moderate duration | More than 6 hours (moderate duration) | Minimal impact from food intake |
Here is a comparison of the duration of action of various PDE5 inhibitors:
Vardenafil (Levitra®)
Vardenafil is very similar to sildenafil but has a few differences. It is typically taken in doses of 10 or 20 mg, and the onset of action is usually around 30 minutes. Its plasma half-life ranges from about 4 to 6 hours, and its effective duration is roughly 4 to 5 hours—comparable to sildenafil.
One advantage is that vardenafil appears to be less influenced by the presence of a high-fat meal than sildenafil, so the delay in onset is less pronounced.
Tadalafil (Cialis®)
Tadalafil stands apart because of its much longer half-life. With a half-life of approximately 17.5 hours, tadalafil can maintain effective drug levels for up to 24 to 36 hours after dosing. This extended duration has earned it the nickname “the weekend pill,” as it allows for greater spontaneity without needing to time sexual activity so precisely.
Tadalafil’s onset of action is still relatively quick—usually between 30 minutes to 1 hour—but its long half-life means that its effects are sustained far longer than sildenafil or vardenafil.
Another key point is that tadalafil is largely unaffected by food, so it can be taken with or without meals without significant delays in onset or reductions in peak concentration.
Avanafil
Avanafil is the newest member of this class and is notable for its rapid onset. Studies report that avanafil can achieve peak plasma concentrations in as little as 10 minutes, faster than the approximately 30 minutes typical for sildenafil.
While its overall duration of action is more moderate (with effective results lasting more than 6 hours), it does not reach the extended tadalafil window. Avanafil’s fast onset and shorter duration may make it especially appealing for patients who prefer a quick response without a prolonged effect.
When to Take It for Best Results
Sildenafil works best when you take it about 30 minutes to 4 hours before you plan on having sex. Most patients notice an effect around 30 to 60 minutes after taking it. If you want the best chance for a firm erection, plan your dose roughly one hour before sexual activity.
Also, take the pill on an empty stomach if you want it to work faster. High‐fat meals can slow its absorption. That delay happens because food slows the rise in the drug’s blood levels. When you eat a large, fatty meal, the peak effect can be delayed by about an hour and the maximum level may drop by almost 30%.
Avoiding heavy meals before taking your dose is best for a quicker start.
Wrap Up
Sildenafil works fast and lasts for several hours, but the exact timing depends on different factors. Most people feel its effects in about 30 minutes, with peak strength around an hour later.
The drug remains active for up to four hours, though its power fades over time. Age, metabolism, food, and medications all influence how long it stays in your system.
If you want the best results, take it on an empty stomach about an hour before sexual activity. High-fat meals and certain medications can slow or extend its effects.
Frequently Asked Questions
Does Sildenafil work without arousal?
No, Sildenafil only helps with erections when you’re sexually aroused. It doesn’t increase libido or automatically cause an erection.
Are there alternatives to Sildenafil?
Yes. Other ED medications like Tadalafil (Cialis), Vardenafil (Levitra), and Avanafil (Stendra) work similarly. Lifestyle changes and therapy may also help.
Can I take Sildenafil with alcohol?
Drinking alcohol, especially in large amounts, can reduce Sildenafil’s effectiveness and increase side effects like dizziness and low blood pressure.
What are common side effects of Sildenafil?
Common side effects include headaches, flushing, dizziness, stuffy nose, and upset stomach. Rare but serious effects include vision changes and prolonged erections.
Can women take Sildenafil?
Sildenafil is not FDA-approved for women. Some research has explored its use for female sexual dysfunction, but results are unclear.
Can I take Sildenafil every day?
Sildenafil is typically taken as needed, not daily. If you need a daily ED medication, Tadalafil (Cialis) might be a better option—talk to your doctor.
Sources
- Eardley, I., Ellis, P., Boolell, M., & Wulff, M. (2002). Onset and duration of action of sildenafil for the treatment of erectile dysfunction. British Journal of Clinical Pharmacology, 53(Suppl 1), 61S–65S. https://doi.org/10.1046/j.0306-5251.2001.00034.x.
- U.S. Food and Drug Administration. (2007). Viagra (sildenafil citrate) prescribing information. Retrieved from https://www.accessdata.fda.gov/drugsatfda_docs/label/2007/020895s027lbl.pdf.
- Muirhead, G. J., Wilner, K., Colburn, W., Haug-Pihale, G., & Rouviex, B. (2002). The effects of age and renal and hepatic impairment on the pharmacokinetics of sildenafil citrate. British Journal of Clinical Pharmacology, 53(Suppl 1), 21S–30S. https://doi.org/10.1046/j.0306-5251.2001.00029.x.
- Nichols, D. J., Muirhead, G. J., & Harness, J. A. (2002). Pharmacokinetics of sildenafil after single oral doses in healthy male subjects: Absolute bioavailability, food effects, and dose proportionality. British Journal of Clinical Pharmacology, 53(Suppl 1), 5S–12S. https://doi.org/10.1046/j.0306-5251.2001.00027.x.
- Smith-Harrison, L. I., Patel, A., & Smith, R. P. (2016). The devil is in the details: An analysis of the subtleties between phosphodiesterase inhibitors for erectile dysfunction. Translational Andrology and Urology, 5(2), 181–186. https://doi.org/10.21037/tau.2016.03.01.