Two of the most common treatments for Erectile Dysfunction are vardenafil and sildenafil. They may seem similar, but they have key differences in strength, speed, and how long they last.
So, which one is better for you? Which acts faster? Which lasts longer? Which causes fewer side effects?
In this article, you’ll learn how each drug works, how fast they act, how effective they are, and what to expect when you take them.
| 🔑 Key Takeaways ➤ Sildenafil can start working in as little as 12 minutes but usually acts within 30 minutes, while vardenafil takes about 30 to 60 minutes to begin working. ➤ Vardenafil’s effects last about 4 to 5 hours, but sildenafil can stay strong for up to 12 hours in some men, with most benefit in the first 4 hours. ➤ The usual dose for vardenafil is 10 mg (up to 20 mg), and for sildenafil it is 50 mg (up to 100 mg), with both taken only once a day. ➤ Both drugs can cause common side effects like headache, flushing, and stomach upset, and rare serious problems such as sudden vision loss or chest pain. ➤ Taking these medicines on an empty stomach may help them work faster, and men over 65 or with other health issues often start at lower doses. |
How It Works
Vardenafil and sildenafil both help with erections by blocking the PDE5 enzyme, but vardenafil is stronger and more selective.
Vardenafil
Vardenafil works by targeting a specific enzyme called phosphodiesterase type 5, or PDE5. This enzyme normally breaks down a substance in the body called cyclic guanosine monophosphate (cGMP), which plays a key role in controlling blood flow.
According to a study, vardenafil inhibits PDE5 very strongly, with an IC50 of just 0.89 nanomolar, showing how little of the drug is needed to block the enzyme’s activity. That’s important, because when PDE5 is blocked, cGMP stays active longer. This leads to relaxation of the smooth muscle in the penis, which allows blood to flow in and cause an erection—but only if sexual stimulation happens first.
Why does stimulation matter? Because it starts the release of nitric oxide, which is what triggers the production of cGMP in the first place. Without that step, the drug has no effect.
One study also found that vardenafil was very selective to PDE5 compared to other enzymes, giving it a safety margin of over 33,000 times. That means it’s highly targeted in how it works, which lowers the risk of side effects from hitting the wrong enzyme.
So, vardenafil helps increase and prolong the effects of cGMP in the penile tissue, making it easier to achieve and maintain an erection during sexual activity.
Sildenafil
Sildenafil works in a very similar way to vardenafil. It mimics the shape of cGMP and competes with it at the site where PDE5 breaks it down.
According to research, this competitive inhibition stops PDE5 from doing its usual job, which allows cGMP to build up inside the smooth muscle cells. When that happens, something amazing occurs: smooth muscle starts to relax. That’s because cGMP activates a protein kinase, which lowers calcium levels inside the cells, makes potassium move out, and stops another protein that causes the muscle to tighten. The result? More blood can flow into the corpus cavernosum—the spongy area in the penis that fills with blood during an erection.
Sildenafil’s effects only happen if nitric oxide is released through sexual stimulation. That nitric oxide boosts cGMP production, and sildenafil just helps the cGMP stick around longer. If there’s no stimulation, there’s no nitric oxide, and that means no erection.
PDE5 is the main enzyme responsible for breaking down cGMP in the penis, which is why inhibiting it is so effective. Sildenafil has a very specific target and doesn’t cause unwanted muscle relaxation in areas like the bladder or the heart. This selectivity helps keep it safer for patients.
Onset and Duration
Vardenafil usually starts working in 30–60 minutes and lasts about 4–5 hours, while sildenafil can start as fast as 12–30 minutes and may remain effective for up to 12 hours.
| Onset of Action | Duration of Effect | |
| Vardenafil | 15–60 minutes (typically ~30–60 mins) | About 4–5 hours |
| Sildenafil | 12–30 minutes (typically ~27 mins) | 4 hours strong, up to 8–12 hours |
Vardenafil
Vardenafil acts fast. According to a study, some men reached peak plasma concentrations in as little as 15 minutes after taking a single oral dose. Most patients, however, reached peak levels around 0.6 to 0.9 hours, or roughly 36 to 54 minutes. The median time to reach this peak (Tmax) was consistently under an hour across various doses—0.66 hours for 20 mg and 0.68 hours for 40 mg.
These numbers suggest that vardenafil can start working quickly, which may come as a relief if you’re hoping for minimal wait time before intimacy.
But how long does the effect last? The half-life—the time it takes for the drug concentration in the body to reduce by half—averaged between 4 to 5 hours.
In practice, the effective window for vardenafil is about 4 hours. This gives you a practical period in which to expect results without feeling rushed. Also, one study noted that 50% of users achieved an erection within 30 minutes after taking the drug. However, they advised that a high-fat meal could delay the onset by about 1 hour and reduce peak concentration by 18%.
That’s why patients are often told to take it on an empty stomach for best results.
So, when should you plan for sexual activity? Ideally, 30 to 60 minutes after taking vardenafil, preferably on an empty stomach. And once it kicks in, you can expect effectiveness to last up to 4 or 5 hours, though this may vary slightly depending on your metabolism, food intake, and other factors.
Sildenafil
Sildenafil isn’t far behind when it comes to how fast it works. One study found that in a study of men with erectile dysfunction, the median onset of action was 27 minutes, with some men responding as early as 12 minutes after taking a 50 mg dose. In fact, 71% of participants achieved erections within 30 minutes, and 82% responded within 45 minutes. That’s a quick response time—especially when you’re planning sexual activity and want predictability.
But how long does it last? One study discovered that sildenafil can remain effective for up to 12 hours in some men, although its peak performance is generally within the first 4 hours. Self-reported erection duration averaged 33 minutes at 1 hour, 23 minutes at 8 hours, and 16 minutes at 12 hours after dosing. Objectively, RigiScan measurements showed erections with ≥60% rigidity lasted 26 minutes at 1 hour, 11 minutes at 8 hours, and 8 minutes at 12 hours.
While sildenafil’s plasma half-life is around 3 to 5 hours, the clinical window—the time you may experience its effects—can stretch beyond that. For most men, it’s safest to expect a strong response for up to 4 hours, with diminishing effects up to 8 or even 12 hours depending on individual factors.
So, sildenafil kicks in fast—often within 30 minutes, sometimes as soon as 12 minutes—and lasts long enough to give you a flexible 4- to 12-hour window for planned intimacy, especially when taken on an empty stomach.
Efficacy
Vardenafil and sildenafil both improve erections, but vardenafil shows strong results even in men with health issues, while sildenafil has proven long-term success and high user satisfaction.
Vardenafil
According to a study, vardenafil significantly improved erectile function in a broad group of European men. Using a flexible dosing strategy, they found that vardenafil raised the IIEF-EF domain score from moderate ED levels closer to mild ED—while placebo barely changed outcome. That’s a notable difference.
Also, 80% to 86% of men using vardenafil reported improved erections, compared to just 21% to 36% with placebo. Vardenafil users reported 84% success by weeks 8 and 12, while the placebo group hit only 49–53%. For maintaining an erection, the success rate was 58% to 74% with vardenafil, versus just 22% to 34% on placebo.
These results were echoed in another study in which they tested a 20 mg dose of vardenafil in 573 men, many of whom had common health issues like diabetes and hypertension. A striking 81% of them achieved successful penetration after the first dose, and 70% were able to maintain their erections. Even more impressive, these numbers increased by the end of the study—85% for penetration and 78% for maintenance.
Clearly, vardenafil delivers consistent results, even for men facing difficult medical conditions.
Sildenafil
In contrast, the long-term effectiveness of sildenafil was studied. For example, over four years, 979 men took sildenafil with flexible doses. At every yearly check-in, over 94% of them said they were satisfied with how it worked for their erections. Nearly every one of those men also said it helped them engage in sexual activity. These are strong results for a medication used over such a long time.
Another study also backed this up by pooling results from 11 double-blind, placebo-controlled trials with 2,667 men. They confirmed that sildenafil led to significantly better erectile function scores than placebo. Whether it was measured by the IIEF, general questions, or patient event logs, sildenafil proved effective. The improvement was reliable and broad across different age groups and ED causes.
Dosage
Vardenafil starts at 10 mg and maxes out at 20 mg once daily, while sildenafil starts at 50 mg with a max of 100 mg once daily, both adjustable based on need and tolerance.
| Medication | Starting Dose | Dose Range | Max Dose | Frequency |
| Vardenafil (Levitra) | 10 mg | 5 mg – 20 mg | 20 mg | Once per day |
| Sildenafil (Viagra) | 50 mg | 25 mg – 100 mg | 100 mg | Once per day |
Vardenafil
Vardenafil offers a flexible dose range. The standard starting dose is 10 mg taken orally once a day, about 60 minutes before sex. This dose can be increased to a maximum of 20 mg or decreased to 5 mg, depending on how well it works for you and whether any side effects appear. Just like sildenafil, vardenafil should not be taken more than once per day.
Special consideration is given to men aged 65 or older. For them, the initial dose should be reduced to 5 mg, taken as needed. The same lower dose applies to patients using alpha-blockers or those with moderate liver disease, since the drug’s effects can be stronger in these situations. In cases of severe liver dysfunction, vardenafil should be avoided entirely.
One unique feature of vardenafil is the availability of an orally disintegrating tablet (ODT). However, the ODT version isn’t interchangeable with the regular 10 mg film-coated tablets. In fact, men who need a dose higher or lower than 10 mg should use only the film-coated version.
And here’s a tip: the ODT tablet should be taken without liquid, and only right after removing it from the packaging.
Just like with sildenafil, sexual stimulation is necessary for vardenafil to work. So, if you’re thinking of trying it, remember—it won’t trigger an erection automatically.
Sildenafil
Sildenafil is available in three tablet strengths—25 mg, 50 mg, and 100 mg. According to the NHS, the typical starting dose for most men is 50 mg, taken when needed. You’re supposed to take it up to four hours before sexual activity, but it’s most effective on an empty stomach. If necessary, your dose can be increased to 100 mg or lowered to 25 mg depending on how well it works and how your body reacts. Importantly, you must not take more than one dose per day. This daily limit helps reduce the chance of side effects like headaches or vision changes.
Do you need sildenafil for something other than ED? For pulmonary hypertension, the dosing is very different. Adults typically take 20 mg three times a day. For children, the dose depends on their weight and ranges from 10 mg to 20 mg, also three times daily. Whether in tablet or liquid form, the instructions are clear: stick to the prescribed amount and don’t double up if you miss a dose.
Side Effects
Vardenafil and sildenafil share common side effects like headache and flushing, but vardenafil has a longer list of possible mild symptoms, while both can cause serious issues like vision loss or allergic reactions.
Vardenafil
Common side effects:
- Flushing (warmth or redness of the face, neck, arms, chest)
- Stuffy or runny nose
- Sneezing
- Headache
- Indigestion
- Dizziness
- Nausea
Less common or bothersome side effects:
- Abnormal or blurred vision
- Back pain
- Muscle aches or stiffness
- Eye pain
- Increased sensitivity to light
- Color vision changes
- Diarrhea
- Heartburn or sour stomach
- Dry mouth or sore throat
- Sleepiness or drowsiness
- Joint pain
- Neck pain
- Hoarseness
- Cough
- Congestion
- Feeling of spinning (vertigo)
- Burning or tingling sensations in the skin
- Belching
- Bloody nose
- Increased redness of the eye
- Difficulty swallowing
- Pain in throat or stomach
- Watery eyes
- Voice changes
- Loss of appetite
- General feeling of being unwell
Serious side effects (seek immediate medical help):
- Chest pain, discomfort, or tightness
- Cold sweats
- Confusion
- Fainting or dizziness when standing
- Irregular, pounding, or fast heartbeat
- Severe headache
- Sudden decrease or loss of vision
- Eye pain or tearing
- Sudden hearing loss
- Vomiting
- Swelling of the face, lips, tongue, or eyelids
- Difficulty breathing or swallowing
- Rash, hives, or itching
- Unusual tiredness or weakness
Sildenafil
Common side effects:
- Headache
- Nausea (feeling sick)
- Flushing (including hot flushes)
- Indigestion
- Stuffy or blocked nose
- Dizziness
Serious side effects:
- Sudden decrease or loss of vision
- Chest pain (especially during or after sex)
- Seizure or fit
- Prolonged or painful erection lasting more than 2 hours
Signs of a serious allergic reaction (anaphylaxis):
- Swelling of the lips, mouth, throat, or tongue
- Difficulty breathing or fast, wheezy breathing
- Tight throat or trouble swallowing
- Blue, grey, or pale skin (especially lips, hands, or feet)
- Sudden confusion, drowsiness, or fainting
- Rash that is swollen, itchy, blistered, or peeling
- Child becoming limp, floppy, or unresponsive
Wrap Up
If you need a fast start with a shorter window, vardenafil might suit your plans. On the other hand, sildenafil can give you a longer window—sometimes up to half a day.
Both options rely on natural stimulation, so plan around your schedule.
Frequently Asked Questions
Do I need a prescription to buy these meds?
Yes. Both vardenafil and sildenafil require a prescription. Don’t buy unapproved versions online—they could be unsafe.
Can these medications cure erectile dysfunction?
No. They help you get an erection when sexually aroused, but they don’t cure ED or increase desire.
Can I take these pills every day?
Only once every 24 hours, unless your doctor says otherwise. Taking more can raise your risk of side effects.
What if the medication doesn’t work for me?
You may need a different dose or another treatment. Talk to your doctor—they can help adjust your plan.
Can I drink alcohol with sildenafil or vardenafil?
It’s best to limit alcohol. Drinking too much can lower blood pressure and make side effects worse.
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