Sildenafil vs Tadalafil vs Vardenafil: How the Three ED Tablets Really Differ

Sildenafil, tadalafil and vardenafil are the three erectile dysfunction tablets most men will be offered, under the brand names Viagra, Cialis and Levitra. They work the same way, and in placebo-controlled trials all three clearly beat placebo. The useful differences are in timing, in which side effects you are more likely to get, in a handful of safety warnings that apply to only one of them, and, in the US at least, in price.

This guide puts the three side by side using their US prescribing information, the direct comparison trials that exist, and two recent large analyses. Where the evidence is thin, we say so. It also corrects an older version of this page, which claimed vardenafil works faster than the others and quoted success rates we could not trace to any source.

The short answer

Sildenafil and vardenafil are short-acting tablets: both reach their peak in the blood about an hour after a dose and have half-lives of about 4 to 5 hours. Tadalafil peaks later (median 2 hours) but lasts far longer, with a half-life of 17.5 hours and trial evidence of improved erections up to 36 hours after a dose. It is also the only one approved as a low daily dose and the only one that is not affected by a heavy meal.

On how well they work, the differences are small. A 2026 network meta-analysis put sildenafil slightly ahead, and in trials that compared tadalafil directly with sildenafil the two worked about equally well, while men who tried both strongly preferred tadalafil. Side effects differ more: flushing is much more common with sildenafil and vardenafil, while indigestion, back pain and muscle aches are more typical of tadalafil. Vardenafil carries a heart rhythm (QT) warning the other two do not have, and in a large telehealth database men on vardenafil reported side effects more often. There is no good evidence that vardenafil works faster than sildenafil.

The three drugs and their names

	Sildenafil	Tadalafil	Vardenafil
Original brand	Viagra (FDA approval 1998)	Cialis (2003)	Levitra (2003)
US tablet strengths	25, 50, 100 mg	2.5, 5, 10, 20 mg	2.5, 5, 10, 20 mg; 10 mg dissolving tablet
Usual starting dose (as needed)	50 mg	10 mg	10 mg
Maximum dose	100 mg once a day	20 mg once a day	20 mg once a day
Daily low-dose option	No	Yes, 2.5 or 5 mg	No
Other approved uses	Pulmonary arterial hypertension (as Revatio, 20 mg)	Enlarged prostate (BPH); pulmonary arterial hypertension (as Adcirca)	None
Examples of Indian generics	Cenforce, Fildena, Kamagra	Vidalista, Tadalista, Tadacip	Filitra, Vilitra, Zhewitra

Vardenafil is the active ingredient in Levitra, so a vardenafil tablet is the same drug as Levitra. The Levitra brand is no longer marketed in the US, where FDA-approved generic vardenafil is sold instead. The Indian brands in the last row are not approved by the FDA, MHRA, TGA or Health Canada.

How all three work

Sexual arousal releases nitric oxide in the penis, which raises a messenger molecule called cGMP. cGMP relaxes the smooth muscle in the blood vessels so blood can flow in and an erection forms. The enzyme PDE5 breaks cGMP down. All three drugs block PDE5, so cGMP lasts longer and the erection is easier to get and keep.

Two consequences follow for all three. None of them causes an erection without arousal. And because nitrate heart medicines work through the same nitric oxide pathway, combining any PDE5 inhibitor with a nitrate can drop blood pressure dangerously, which is why that combination is contraindicated for all three.

Timing side by side

From the US labels	Sildenafil	Tadalafil	Vardenafil
Time to peak blood level (median, fasting)	60 min (range 30 to 120)	2 hours (range 30 min to 6 hours)	60 min (range 30 to 120)
Half-life	About 4 hours	17.5 hours	About 4 to 5 hours
When to take it, per label	About 1 hour before sex; anywhere from 30 min to 4 hours before	At least 30 min before; erections improved up to 36 hours after	About 60 min before sex
High-fat meal	Peak 29% lower and about 1 hour later	No effect	Peak 18% to 50% lower

Sildenafil and vardenafil reach their peak at the same median time, an hour, which is why the old claim that vardenafil "works faster" does not hold up. Neither label reports a trial showing an earlier onset for one over the other.

Tadalafil has the most direct onset data. In a stopwatch study in the Cialis label, 52% of men on 20 mg had a successful erection within 30 minutes, against 35% on placebo. At the other end, in a trial where men tried at fixed times after a single 20 mg dose, 61% had at least one successful attempt at 24 hours and 64% at 36 hours, against 37% on placebo at both points. That long window, not a faster start, is tadalafil's real advantage.

Does food matter?

For tadalafil, no: the label says it can be taken with or without food, and a meal did not change its absorption. For sildenafil, a high-fat meal cut the peak blood level by 29% and delayed it by about an hour. Vardenafil was also affected: two food-effect studies found the peak was 18% to 50% lower after a high-fat meal. In practice, if you take sildenafil or vardenafil after a big dinner, expect it to take longer and possibly work less well than on an empty stomach.

How well each one works

The labels report efficacy using different questionnaires and trial designs, so their headline numbers cannot be lined up against each other. Within each programme, the effect over placebo is large:

Label trial	Measure	Placebo	Drug
Vardenafil, North American trial, 3 months	Erection lasting to successful intercourse (SEP3)	32%	10 mg: 64%; 20 mg: 65%
Tadalafil 20 mg, US Study A	SEP3 at endpoint	25%	50%
Tadalafil 20 mg, US Study B	SEP3 at endpoint	23%	64%

The best attempt to compare all of them on one scale is a 2026 network meta-analysis by Salonia and colleagues of 83 placebo-controlled trials (PMID 42296271). It estimated the odds of reaching normal erectile function against placebo for each dose. Sildenafil 100 mg came out highest (odds ratio 9.06), followed by sildenafil 50 mg (7.90), vardenafil 10 mg (7.78) and tadalafil 20 mg (7.13). The authors concluded that sildenafil was significantly more effective, but the estimates for the top doses are close, and a network meta-analysis compares drugs across different trials rather than within one. For most men the honest reading is that any of the three works, and a man who does not respond to one should be reviewed by a doctor before concluding that none will.

Direct comparison trials

Most head-to-head trials compared tadalafil with sildenafil. A 2017 meta-analysis of 16 such trials (Gong and colleagues, PMID 28741090) found the two worked about equally well. Preference was different: in the studies that asked men which drug they preferred after trying both, the pooled odds of choosing tadalafil were about eight times higher (odds ratio 8.04, 95% CI 4.99 to 12.96, from the paper's tables). Our tadalafil vs sildenafil comparison covers that evidence in detail.

Vardenafil has much less direct comparison data. The largest recent source is a retrospective analysis of about 132,000 men treated through a direct-to-consumer telehealth platform (Rodler and colleagues, 2026, PMID 41261009). In that dataset, medium and high doses of sildenafil (50 and 100 mg) produced slightly larger patient-reported improvements in satisfaction and erection hardness than tadalafil 10 and 20 mg, a statistically significant but modest difference. Efficacy for vardenafil was not compared. This is self-reported data from a relatively healthy population, not a randomised trial, so it adds to the trial evidence rather than replacing it.

Side effects side by side

The side effects are shared because they come from PDE5 blocking in other tissues: widened blood vessels cause headache, flushing and a blocked nose, and relaxed muscle at the lower end of the gullet causes indigestion. The proportions differ. The table uses each label's main as-needed trial table; the trials were separate, so read the gap over placebo rather than comparing raw rates across columns.

Side effect	Sildenafil (flexible dose) vs placebo	Tadalafil 20 mg vs placebo	Vardenafil 5 to 20 mg vs placebo
Headache	16% vs 4%	15% vs 5%	15% vs 4%
Flushing	10% vs 1%	3% vs 1%	11% vs 1%
Indigestion	7% vs 2%	10% vs 1%	4% vs 1%
Blocked or runny nose	4% vs 2% (nasal congestion)	3% vs 1% (nasal congestion)	9% vs 3% (rhinitis)
Back pain	2% vs 2%	6% vs 3%	2.0% vs 1.7% (stated in the label text)
Muscle aches	Not listed in this table	3% vs 1%	Not listed
Abnormal vision	3% vs 0%	Not listed	Not listed

"Not listed" means the reaction did not reach the label's 2% threshold or was not more common than on placebo in that table. Flushing is the clearest difference: about 9 to 10 percentage points above placebo with sildenafil and vardenafil, 2 with tadalafil. The direct comparison meta-analysis agrees, with the odds of flushing about 60% lower on tadalafil than on sildenafil (odds ratio 0.39). Indigestion runs the other way.

Which one men report more side effects with

In the Rodler telehealth database, the share of patients reporting any side effect was similar for tadalafil (33.9%) and sildenafil (35.0%) but higher for vardenafil (47.4%). Nasal congestion was the most common complaint on all three at medium and high doses, and reflux was more common with tadalafil than with sildenafil (8.0% vs 5.3%).

The vardenafil group was small (565 men), and patients on a telehealth platform are not randomly assigned to a drug, so this is a signal rather than proof. It is consistent with the 2026 network meta-analysis, which also found the odds of treatment-related side effects highest for vardenafil and lowest for tadalafil.

Vision changes and the PDE6 enzyme

The retina uses a related enzyme, PDE6, to process light. The less selective a drug is for PDE5 over PDE6, the more likely it is to cause temporary vision changes such as a blue or green tinge, light sensitivity or blurring. Sildenafil is only about 10 times more potent at PDE5 than at PDE6, vardenafil more than 15 times, and tadalafil 700 times.

The trial data follow the same pattern. With sildenafil, abnormal vision was reported by 3% of men in the flexible-dose trials and by 11% at 100 mg in the fixed-dose trials. With tadalafil, changes in colour vision were rare (under 0.1% across its clinical studies). These effects are temporary. A separate and rare problem, sudden loss of vision from non-arteritic anterior ischaemic optic neuropathy (NAION), appears in all three labels; observational studies of PDE5 inhibitors as a class found about a twofold increase in risk shortly after use. Sudden vision loss in one or both eyes means stopping the drug and getting urgent medical help.

Back pain and muscle aches with tadalafil

Back pain and muscle aches are the side effects most specific to tadalafil. The label describes them as a diffuse ache in the lower back, buttocks or thighs, usually starting 12 to 24 hours after a dose and settling within 48 hours, generally mild or moderate and eased by paracetamol (acetaminophen) or an anti-inflammatory. About 0.5% of men on as-needed tadalafil stopped treatment because of it. In the direct comparison meta-analysis, muscle aches were clearly more common on tadalafil than on sildenafil (odds ratio 4.89), and back pain also more common (1.79).

The heart rhythm warning that applies only to vardenafil

Vardenafil's label carries a QT prolongation warning that the other two do not. In a study in healthy men, both 10 mg and 80 mg of vardenafil lengthened the QT interval of the heart's electrical cycle by a similar amount to the antibiotic moxifloxacin, and when vardenafil was combined with another drug that has a similar QT effect, the effects added up. The label says men taking class IA antiarrhythmics (such as quinidine or procainamide) or class III antiarrhythmics (such as amiodarone or sotalol), and men with congenital QT prolongation, should avoid vardenafil. Anyone with a history of QT prolongation or taking other QT-prolonging medicines should discuss it with a doctor first. For these men, sildenafil or tadalafil is the simpler choice.

Medicines that change the dose

All three are cleared by the liver enzyme CYP3A4, so drugs that block it raise their blood levels. The limits differ:

Taking	Sildenafil	Tadalafil (as needed)	Vardenafil
Ritonavir	25 mg maximum in 48 hours (levels rise 11-fold)	10 mg maximum, once every 72 hours	2.5 mg maximum in 72 hours (levels rise 49-fold)
Ketoconazole or itraconazole	Consider starting at 25 mg	10 mg maximum, once every 72 hours	5 mg in 24 hours at 200 mg a day; 2.5 mg at 400 mg a day
Clarithromycin, indinavir, saquinavir or atazanavir	Consider starting at 25 mg (saquinavir named in the label)	No set limit for most; levels likely rise	2.5 mg maximum in 24 hours
Cobicistat-boosted HIV treatment	Ask your prescriber	Ask your prescriber	2.5 mg maximum in 72 hours
Erythromycin	Consider starting at 25 mg	No set limit; label says levels likely rise	5 mg maximum in 24 hours
Alpha-blocker (for prostate or blood pressure)	Be stable on it first; start at 25 mg	Be stable on it first; start at the lowest dose	Be stable on it first; start at 5 mg (2.5 mg if also on a CYP3A4 inhibitor), and consider spacing the two doses apart

Grapefruit juice also blocks CYP3A4, and the vardenafil label says it would likely increase vardenafil exposure. For daily tadalafil with a strong CYP3A4 blocker, the maximum is 2.5 mg a day.

Nitrates and riociguat: never with any of the three

All three labels make nitrates (nitroglycerin, isosorbide mononitrate or dinitrate, and recreational nitrites such as "poppers") a contraindication, along with riociguat, a guanylate cyclase stimulator used for pulmonary hypertension. If a man who has taken tadalafil develops chest pain and a nitrate is considered medically necessary, the Cialis label says at least 48 hours should have passed since the last dose, and it should be given under close monitoring. The sildenafil and vardenafil labels say the safe interval is not known. In practice, anyone who has taken any of these drugs and develops chest pain should call emergency services and tell them which drug and when.

Can you take two of them together?

No. All three labels advise against combining them with another PDE5 inhibitor or another erectile dysfunction treatment, which has not been studied; the sildenafil label adds that the combination may lower blood pressure further. That includes taking vardenafil and tadalafil on the same day, and it includes combination tablets sold online that contain two PDE5 inhibitors (for example sildenafil plus vardenafil). No regulator has approved such a combination. If one drug is not working, the answer is a dose review or a switch, not stacking. Our guide to Sildalist, which combines sildenafil 100 mg and tadalafil 20 mg, covers the evidence on one such tablet.

Switching from one to another

None of the labels gives a fixed waiting time between stopping one PDE5 inhibitor and starting another, so ask the prescriber. What the pharmacology tells you is that sildenafil and vardenafil are mostly cleared within a day, while tadalafil, with a 17.5-hour half-life, is still present in meaningful amounts for a couple of days after a dose. A man switching away from tadalafil should not take a second drug the next day on the assumption that the first is gone.

Before switching because a drug "did not work", check the basics: was it taken on an empty stomach (for sildenafil and vardenafil), was there sexual stimulation, and was it tried on several occasions at an adequate dose. In one study of 60 men who said sildenafil had failed them, 44 (about three quarters) had used it in a way that could explain the failure: too few attempts, a dose below 100 mg, or not knowing that arousal was needed. Of those rechallenged with proper instruction and 100 mg, 58.5% then responded (Jiann and colleagues, PMID 14963473). If a tablet still fails after a fair trial, our guide to ED treatment when tablets don't work covers switching, injections, vacuum devices and implants.

Daily tadalafil: a different approach

Tadalafil is the only one of the three approved as a daily low dose (2.5 or 5 mg taken at about the same time every day, regardless of when sex happens). Steady blood levels mean no timing at all. The 5 mg daily dose is also approved for the urinary symptoms of an enlarged prostate (BPH), so a man with both problems can treat them with one tablet. One caution: the label does not recommend tadalafil together with an alpha-blocker (such as tamsulosin) for BPH, and says a man on an alpha-blocker for BPH should stop it at least a day before starting daily tadalafil, on his prescriber's advice. The trade-off is continuous exposure: the label notes that daily use should be considered when assessing interactions with nitrates, alpha-blockers, blood pressure medicines and heavy alcohol use. Our generic Cialis guide has the daily-dose trial data.

Alcohol

All three widen blood vessels, and so does alcohol. The Cialis label warns that substantial drinking (5 units or more) with tadalafil can increase dizziness on standing, a faster heart rate and lower standing blood pressure. In a vardenafil study, 20 mg did not add to alcohol's effect on blood pressure over 4 hours at a moderate amount of alcohol (about 40 mL of pure alcohol for a 70 kg man). A drink or two is unlikely to matter with any of them; heavy drinking makes dizziness and fainting more likely and also makes erections harder to achieve.

Older men, liver and kidney problems

Situation	Sildenafil	Tadalafil	Vardenafil
Age 65 and over	Consider starting at 25 mg	No adjustment	Consider starting at 5 mg
Liver impairment	Consider starting at 25 mg	Mild or moderate: no more than 10 mg; severe: not recommended	Moderate: start at 5 mg, maximum 10 mg; severe: do not use
Kidney impairment	Severe: consider starting at 25 mg	Moderate: start at 5 mg, maximum 10 mg once every 48 hours; severe or dialysis: 5 mg once every 72 hours, and daily dosing not recommended	Dialysis: do not use (not studied)

Which one fits which situation

If this matters most	The evidence points to	Why
Not having to time it	Tadalafil	Improved erections up to 36 hours; daily low-dose option
Taking it after a meal	Tadalafil	No food effect
Avoiding flushing	Tadalafil	2 points above placebo against 9 to 10
Avoiding back pain, muscle aches or reflux	Sildenafil or vardenafil	These are more typical of tadalafil
Avoiding vision tinge	Tadalafil	700-fold PDE5 selectivity over PDE6
Side effects that wear off quickly	Sildenafil or vardenafil	Half-life about 4 to 5 hours
Also treating an enlarged prostate	Tadalafil 5 mg daily	The only one approved for BPH
Taking antiarrhythmics or with a QT problem	Sildenafil or tadalafil	Vardenafil carries the QT warning
Lowest US pharmacy cost	Sildenafil or tadalafil	Generic vardenafil costs far more (see below)

None of this replaces a doctor's assessment. Erectile dysfunction can be an early sign of heart disease or diabetes, and the doctor needs to know about nitrates, alpha-blockers, antiarrhythmics and antifungal or HIV medicines before prescribing any of the three. For sildenafil trial results in men with diabetes, heart disease, depression or after prostate surgery, see sildenafil results by health condition. Our guide to getting ED medication online covers what an online consultation should ask and what it can miss.

What they cost

In the US, generic sildenafil and tadalafil have become very cheap at pharmacy level, while generic vardenafil has not. The Medicaid National Average Drug Acquisition Cost survey (NADAC), which records what pharmacies pay, showed these medians per tablet as of 7 October 2026:

Generic tablet	NADAC per tablet
Sildenafil 50 mg	$0.107
Sildenafil 100 mg	$0.132
Tadalafil 10 mg	$0.153
Tadalafil 20 mg	$0.167
Tadalafil 5 mg (daily dose)	$0.103
Vardenafil 10 mg	$2.867
Vardenafil 20 mg	$2.793

These are pharmacy costs, not what patients pay, but they explain why US cash prices for generic sildenafil and tadalafil can be low with a prescription and a discount card. A US man with a prescription should compare local prices before ordering any import, and the FDA says that in most circumstances it is illegal for individuals to import drugs for personal use. Outside the US, prices and rules differ by country.

Strengths above the label maximum

Some Indian brands sell vardenafil at 40, 60 or 80 mg and tadalafil at 40 to 80 mg, two to four times the labelled maximum. The large trials stopped at 20 mg for both drugs, and in the vardenafil label's main trial, going from 10 mg to 20 mg raised the rate of successful intercourse only from 64% to 65%. Side effects such as headache and flushing rise with dose. We cover the evidence in our Filitra 40 review and high-dose tadalafil guide. A man who gets no result from the maximum labelled dose needs a medical review, not a stronger tablet.

Who should not take any of them

• Men taking any nitrate or a guanylate cyclase stimulator such as riociguat.
• Men who have been told sexual activity is unsafe for their heart. The labels also single out men with a recent heart attack (within 90 days for tadalafil, 6 months for the others), stroke or life-threatening arrhythmia in the last 6 months, very low resting blood pressure or uncontrolled high blood pressure, unstable angina or angina during sex, and heart failure (for tadalafil, even mild heart failure, NYHA class 2 or worse, in the last 6 months). These men were not included in the trials; the tadalafil and vardenafil labels do not recommend use in them, and the sildenafil label advises caution.
• Men with hereditary degenerative retinal disorders such as retinitis pigmentosa (not studied).
• Men who are allergic to the drug.
• For vardenafil specifically: men with congenital QT prolongation or taking class IA or III antiarrhythmics, and men with severe liver impairment or on dialysis.

Several groups need extra care and a doctor's advice first: men who have had NAION before (the labels say to use these drugs only when the benefit outweighs the risk), men with aortic stenosis or another obstruction to blood flow out of the heart, men with severely impaired control of their blood pressure, and men with a penis deformity or a condition that raises the risk of priapism (sickle cell anaemia, multiple myeloma, leukaemia). Some generic vardenafil tablets contain aspartame (phenylalanine), which matters for men with phenylketonuria. None of the three is approved for women.

When to get urgent help

• An erection lasting more than 4 hours, painful or not. Priapism can permanently damage the penis if not treated quickly.
• Sudden loss or decrease of vision in one or both eyes.
• Sudden decrease or loss of hearing, sometimes with ringing in the ears or dizziness.
• Chest pain, fainting or severe dizziness during or after sex. Tell the emergency team which drug you took and when, because it changes whether they can give a nitrate.

If you have a side effect, report it to your regulator as well as to the seller: FDA MedWatch in the US, the MHRA Yellow Card scheme in the UK, the TGA in Australia or Health Canada's MedEffect.

What about avanafil?

Avanafil (Stendra, Spedra) is a fourth PDE5 inhibitor. Its US label allows dosing as early as about 15 minutes before sex at the higher doses, which no other label does. In the 2026 network meta-analysis its estimated effect at 100 and 200 mg was smaller than the top doses of the other three. Our avanafil guide covers its trials, and the erectile dysfunction treatment page compares all the options.

Sources

• VIAGRA (sildenafil citrate) tablets, US prescribing information, sections 2, 4, 5, 6.1, 7, 12.1 to 12.3. DailyMed
• CIALIS (tadalafil) tablets, US prescribing information, sections 1, 2, 4, 5, 6.1, 7, 12.1 to 12.3 and 14. DailyMed
• Vardenafil hydrochloride tablets (Lannett), US prescribing information, July 2026, sections 2, 4, 5, 6.1, 7, 8, 12 and 14. DailyMed
• Salonia A et al. A comparative evaluation of on-demand phosphodiesterase-5 inhibitor efficacy in erectile dysfunction treatment: a systematic review and network meta-analysis. Journal of Sexual Medicine 2026;23(7). PMID 42296271.
• Rodler S et al. Head-to-head comparison of the safety and efficacy profiles of three phosphodiesterase type 5 inhibitors through patient-reported outcomes of 130 000 patients from a direct-to-consumer platform database. European Urology Focus 2026;12(2):217-226. PMID 41261009.
• Jiann BP et al. Rechallenge prior sildenafil nonresponders. International Journal of Impotence Research 2004;16(1):64-8. PMID 14963473.
• Gong B et al. Direct comparison of tadalafil with sildenafil for the treatment of erectile dysfunction: a systematic review and meta-analysis. International Urology and Nephrology 2017;49(10):1731-1740. PMID 28741090.
• Centers for Medicare and Medicaid Services. National Average Drug Acquisition Cost (NADAC), 2026 file, as of 7 October 2026. data.medicaid.gov
• US Food and Drug Administration. Personal Importation. FDA

This guide is for information only and is not medical advice. Sildenafil, tadalafil and vardenafil are prescription medicines; speak to a doctor or pharmacist before using any of them.