Vardenafil is an oral phosphodiesterase type 5 (PDE5) inhibitor used to treat erectile dysfunction (ED). Bayer sold it as Levitra, a film-coated tablet the FDA approved in August 2003, and later as Staxyn, a 10 mg tablet that dissolves on the tongue. It works the same way as sildenafil (Viagra) and tadalafil (Cialis), and its 4–5 hour half-life is close to sildenafil’s.
The most important current fact is regulatory. Bayer stopped selling both brands in the US, and the FDA withdrew approval of the Levitra and Staxyn applications as of July 3, 2024, at the company’s request. The FDA had already determined that the products were not withdrawn for safety or effectiveness reasons, so generic vardenafil tablets and orally disintegrating tablets remain on the US market. In the EU, Levitra is still authorised.
This page summarizes what the FDA labels, the clinical trials and the regulators report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Phosphodiesterase type 5 (PDE5) inhibitor |
| Brands / approval | Levitra (Bayer): FDA August 19, 2003 (NDA 021400); EU March 6, 2003. Staxyn ODT: FDA June 17, 2010 (NDA 200179) |
| US brand status | Levitra and Staxyn discontinued; FDA approval of both NDAs withdrawn as of July 3, 2024, at Bayer’s request. Generics available |
| Route | Oral film-coated tablet; 10 mg orally disintegrating tablet (ODT) |
| Strengths | Tablets 2.5, 5, 10 and 20 mg; ODT 10 mg |
| Labeled dose (tablet) | 10 mg as needed about 60 min before sex (range 5–20 mg), at most once a day; consider 5 mg at age 65 or older |
| Time to peak | Median 60 min for tablets (fasted); median 1.5 h for the ODT |
| Half-life (label) | About 4–5 h, for vardenafil and its main metabolite M1 |
| Metabolism | Mainly CYP3A4, with CYP3A5 and CYP2C contributing |
| WADA status | Not on the 2026 Prohibited List |
What it is
Vardenafil has the formula C₂₃H₃₂N₆O₄S and a molecular weight of 488.6 g/mol (PubChem). Products contain it as the hydrochloride salt. Each Staxyn tablet, for example, holds 11.85 mg of vardenafil hydrochloride, equivalent to 10 mg of vardenafil (Staxyn label).
Mechanism
The Levitra label describes erection as a blood-flow event (Levitra label):
- sexual stimulation releases nitric oxide from nerve endings and blood-vessel lining in the penis;
- nitric oxide activates guanylate cyclase, which raises cyclic GMP (cGMP) in smooth muscle;
- cGMP relaxes the smooth muscle, so more blood flows into the penis.
PDE5 is the main enzyme that breaks down cGMP in this tissue. Blocking it lets cGMP build up and strengthens the erection response. Because the process starts with nitric oxide released during arousal, the label states that vardenafil has no effect without sexual stimulation.
Selectivity
The label reports these in-vitro selectivity figures for PDE5 over other phosphodiesterases:
| Enzyme | Selectivity for PDE5 over it |
|---|---|
| PDE6 (retina) | More than 15-fold |
| PDE1 | More than 130-fold |
| PDE11 | More than 300-fold |
| PDE2, 3, 4, 7, 8, 9, 10 | More than 1,000-fold |
PDE6 works in the rods and cones of the retina. The label ties the brief, dose-related blue/green color-discrimination changes seen around peak levels to inhibition of this enzyme.
Pharmacokinetics
From the Levitra label:
| Parameter | Value |
|---|---|
| Absolute bioavailability | About 15% |
| Time to peak (20 mg, fasted) | 30 min to 2 h, median 60 min |
| Effect of a high-fat meal | Peak level (Cmax) 18–50% lower |
| Volume of distribution | 208 L |
| Protein binding | About 95% (vardenafil and M1) |
| Main metabolite | M1 (desethyl-vardenafil): about 26% of parent levels, 28% of its PDE5 potency, ≈7% of total activity |
| Terminal half-life | About 4–5 h (vardenafil and M1) |
| Excretion | 91–95% of the dose in feces, 2–6% in urine, as metabolites |
Some groups have higher exposure:
| Group | Change vs reference |
|---|---|
| Men 65 and older (vs 18–45) | Cmax +34%, AUC (total exposure) +52% |
| Mild hepatic impairment (Child-Pugh A) | Cmax +22%, AUC +17% |
| Moderate hepatic impairment (Child-Pugh B) | Cmax +130%, AUC +160% |
| Creatinine clearance under 50 mL/min | AUC 20–30% higher |
The orally disintegrating tablet is not the same dose
The Staxyn label states that the 10 mg ODT is not interchangeable with the 10 mg film-coated tablet, because it gives higher systemic exposure. In healthy men, the ODT’s Cmax was 15% higher and its AUC 44% higher than the 10 mg tablet (Staxyn label). The ODT is taken on the tongue without liquid: swallowing it with water cut AUC by 29%. A high-fat meal did not change its AUC but lowered Cmax by 35%.
Regulatory status
- 2003. The EU authorised Levitra on March 6, 2003, and the FDA approved it on August 19, 2003 (EMA; 88 FR 27901).
- 2010. The FDA approved Staxyn 10 mg ODT on June 17, 2010, as a new dosage form (Drugs@FDA, NDA 200179).
- 2018–2021. Bayer told the FDA it was discontinuing the Levitra strengths one by one. In 2023 the FDA determined that Levitra was not withdrawn for reasons of safety or effectiveness, which lets generic approvals continue (88 FR 27901). It made the same determination for Staxyn in April 2024 (89 FR 24841).
- July 3, 2024. At Bayer’s request, the FDA withdrew approval of NDA 021400 (Levitra 2.5, 5, 10 and 20 mg) and NDA 200179 (Staxyn 10 mg), noting that the products were no longer marketed (89 FR 47566).
Generic vardenafil film-coated tablets and 10 mg ODTs carry current US labels with the same indication, dosing and warnings (DailyMed, Zydus tablets; DailyMed, Alembic ODT). The clinical data below come from the final Bayer labels (March and April 2023), which the generic labels follow.
Approved medical use
Vardenafil has a single US indication: treatment of erectile dysfunction. It is not indicated for women or children.
| Situation | Labeled tablet dosing |
|---|---|
| Most men | 10 mg about 60 min before sex; adjust to 5 mg or 20 mg; at most once a day |
| Age 65 or older | Consider starting at 5 mg |
| Moderate hepatic impairment | Start at 5 mg; do not exceed 10 mg |
| Stable on an alpha-blocker | Start at 5 mg (2.5 mg with certain CYP3A4 inhibitors) |
| Severe hepatic impairment or dialysis | Do not use |
The ODT comes only as 10 mg. Its label says men who need a lower or higher dose should use the film-coated tablets. It also says not to start vardenafil with the ODT in men taking alpha-blockers, and not to use the ODT with moderate or strong CYP3A4 inhibitors or in moderate or severe hepatic impairment.
What the research shows
Pivotal trials of the film-coated tablet
The label summarizes four 12-week, double-blind, placebo-controlled, fixed-dose trials in 2,431 men aged 20–83. Outcomes were the erectile function (EF) domain of the International Index of Erectile Function (IIEF, scored 0–30) and two diary questions: getting an erection firm enough for penetration (SEP2) and keeping it long enough for successful intercourse (SEP3).
In the North American trial (762 men), results at 3 months were:
| Arm | EF domain score (baseline ≈13–14) | SEP2 success | SEP3 success |
|---|---|---|---|
| Placebo | 15 | 52% | 32% |
| 5 mg | 18 | 65% | 51% |
| 10 mg | 21 | 75% | 64% |
| 20 mg | 21 | 80% | 65% |
All doses beat placebo (p under 0.0001), and a European trial of 803 men confirmed the results. Gains held at 6 months in the North American trial.
Diabetes and prostate cancer surgery
ED linked to diabetes or prostate surgery is harder to treat, and the label reports separate trials in both groups:
| Trial | Arm | EF domain score | SEP3 success |
|---|---|---|---|
| Diabetes (n = 439 in label) | Placebo | 13 | 23% |
| 10 mg | 17 | 49% | |
| 20 mg | 19 | 54% | |
| After radical prostatectomy (n = 427 in label) | Placebo | 9 | 10% |
| 10 mg | 15 | 37% | |
| 20 mg | 15 | 34% |
The published diabetes trial randomized 452 men. After 12 weeks, 57% (10 mg) and 72% (20 mg) reported improved erections, compared with 13% on placebo (Goldstein et al., Diabetes Care 2003).
The prostatectomy trial randomized 440 men after nerve-sparing surgery; 70% had severe ED at baseline (Brock et al., J Urol 2003). Baseline severity mattered. On 20 mg, the average intercourse success rate was:
- 74% in men with mild to moderate ED, vs 49% on placebo;
- 28% in men with severe ED, vs 4% on placebo.
Pooled analysis
A 2021 meta-analysis of 14 randomized trials (3,221 patients) found that vardenafil raised the IIEF erectile function score by 7.93 points over placebo (95% CI 6.00–9.85). Success rates rose by about 26 percentage points for SEP2 and 35 for SEP3 (Wang et al., Adv Ther 2021). The authors noted that the optimal dose and treatment course had not been established.
The orally disintegrating tablet
Two identical 12-week trials tested the 10 mg ODT against placebo, with about half of the men aged 65 or older (Staxyn label):
| Trial | Arm | EF domain score at endpoint | SEP3 success at endpoint |
|---|---|---|---|
| Study 1 (mainly Europe, n = 355) | Placebo | 14 | 26% |
| ODT 10 mg | 21 | 65% | |
| Study 2 (mainly North America, n = 331) | Placebo | 14 | 27% |
| ODT 10 mg | 21 | 60% |
An integrated analysis of both trials (686 men analyzed) found the ODT superior to placebo regardless of age, baseline ED severity, diabetes, high cholesterol or high blood pressure (Sperling et al., J Sex Med 2011).
How it compares with sildenafil and tadalafil
From the three US labels (Levitra; Viagra; Cialis):
| Feature | Vardenafil | Sildenafil | Tadalafil |
|---|---|---|---|
| Initial US approval | 2003 | 1998 | 2003 |
| Median time to peak (fasted) | 60 min | 60 min | 2 h |
| Terminal half-life | About 4–5 h | About 4 h | 17.5 h |
| High-fat meal | Lowers Cmax 18–50% | Peak about 60 min later; Cmax 29% lower | Rate and extent of absorption not affected |
| Selectivity for PDE5 over PDE6 | More than 15-fold | About 10-fold | 700-fold |
Head-to-head trials and network meta-analyses (which compare drugs indirectly through their placebo-controlled trials) do not agree on a ranking:
| Study | Design | Finding for vardenafil |
|---|---|---|
| Rubio-Aurioles et al., J Sex Med 2006 | Double-blind crossover, vardenafil 20 mg vs sildenafil 100 mg, 931 men with cardiovascular risk factors | Preferred by 38.9% vs 34.5% (26.6% no preference); met noninferiority. EF gain 10.0 vs 9.4, “nominal” significance only |
| Jannini et al., J Sex Med 2009 | Open-label randomized crossover: sildenafil 50 or 100 mg, tadalafil 20 mg, vardenafil 20 mg | No difference between treatments in IIEF score or penile blood-flow measures |
| Yuan et al., Eur Urol 2013 | Network meta-analysis, 118 trials, 31,195 men | Tadalafil and vardenafil ranked most effective; tadalafil beat vardenafil on EF score by 1.49 points (95% CI 0.50–2.50); no major safety differences |
| Chen et al., Eur Urol 2015 | Network meta-analysis, 82 trials, 47,626 men | At starting doses, vardenafil 10 mg had adverse-event rates similar to sildenafil 50 mg but “markedly lower” global efficacy |
| Salonia et al., J Sex Med 2026 | Dose-based network meta-analysis, 83 trials | Sildenafil most effective; odds of treatment-related adverse events highest for vardenafil and lowest for tadalafil, with wide confidence intervals |
Two cautions apply. The 2006 crossover used encapsulated sildenafil, and its efficacy advantages were only nominal. The meta-analyses rest mostly on placebo-controlled trials, not direct comparisons. Overall, no PDE5 inhibitor is consistently best. The clearest practical difference is duration: tadalafil’s half-life (17.5 h) is much longer than vardenafil’s or sildenafil’s (about 4–5 h and 4 h).
Side effects and risks
Common side effects
In placebo-controlled trials of 5–20 mg tablets, these reactions occurred in at least 2% of men and more often than on placebo:
| Reaction | Vardenafil (n = 2,203) | Placebo (n = 1,199) |
|---|---|---|
| Headache | 15% | 4% |
| Flushing | 11% | 1% |
| Rhinitis (stuffy or runny nose) | 9% | 3% |
| Dyspepsia (indigestion) | 4% | 1% |
| Sinusitis | 3% | 1% |
| Flu syndrome | 3% | 2% |
| Dizziness | 2% | 1% |
| Increased creatine kinase | 2% | 1% |
| Nausea | 2% | 1% |
Headache, flushing, dyspepsia, nausea and rhinitis became more common as the dose rose. In these trials, 3.4% of men on vardenafil stopped because of side effects, compared with 1.1% on placebo. In the ODT trials, the most common reactions were headache (14.4% vs 1.8%) and flushing (7.6% vs 0.6%).
Nitrates and riociguat: contraindicated
Vardenafil must not be combined with nitrates (such as nitroglycerin) or other nitric oxide donors, used regularly or occasionally. Both drug types raise cGMP, and together they can drop blood pressure sharply. The label’s patient counseling warns of dizziness, fainting, heart attack or stroke from the combination.
In a label study in 18 healthy men, 20 mg vardenafil was given at different times before 0.4 mg sublingual nitroglycerin:
- blood pressure fell further when vardenafil was given 1 or 4 hours before;
- heart rate rose further when it was given 1, 4 or 8 hours before;
- no added effect was seen when it was given 24 hours before.
The label still states that a safe interval between vardenafil and nitrates “has not been determined.” Use with guanylate cyclase stimulators such as riociguat is also contraindicated.
QT interval
Vardenafil slightly lengthens the corrected QT interval (QTc), the ECG measure of how long the heart takes to recharge between beats. In a crossover study in 59 healthy men aged 45–60, measured 1 hour after dosing (label Table 6):
| Drug | QTc change vs placebo, Fridericia correction (90% CI) |
|---|---|
| Vardenafil 10 mg | +8 ms (6–9) |
| Vardenafil 80 mg | +10 ms (8–11) |
| Moxifloxacin 400 mg (active control) | +8 ms (6–9) |
A published report of a similar study in 58 men found +8 ms for vardenafil 10 mg and +6 ms for sildenafil 50 mg; only moxifloxacin lengthened the uncorrected QT (Morganroth et al., Am J Cardiol 2004). The authors judged the changes clinically irrelevant.
The label notes that the effect can add up with other drugs. Vardenafil 10 mg plus the antibiotic gatifloxacin raised QTcF by 9 ms, compared with 5 ms and 4 ms for each alone. It says men with congenital QT prolongation, or men taking class IA (such as quinidine, procainamide) or class III (such as amiodarone, sotalol) antiarrhythmics, should avoid vardenafil. The clinical impact of these QT changes is unknown.
CYP3A4 inhibitors
Vardenafil is cleared mainly by CYP3A4, so drugs that block this enzyme raise its levels sharply:
| Inhibitor (dose) | Vardenafil dose | AUC increase | Cmax increase | Labeled tablet limit |
|---|---|---|---|---|
| Ritonavir (600 mg twice daily) | 5 mg | 49-fold | 13-fold | 2.5 mg per 72 h |
| Indinavir (800 mg three times daily) | 10 mg | 16-fold | 7-fold | 2.5 mg per 24 h |
| Ketoconazole (200 mg daily) | 5 mg | 10-fold | 4-fold | 5 mg per 24 h (2.5 mg at 400 mg daily) |
| Erythromycin (500 mg three times daily) | 5 mg | 4-fold | 3-fold | 5 mg per 24 h |
Ritonavir also stretched vardenafil’s half-life to 26 hours. The label sets the same 2.5 mg per 72 hour limit for cobicistat, and 2.5 mg per 24 hours for saquinavir, atazanavir, clarithromycin and itraconazole 400 mg daily. It expects grapefruit juice to raise exposure as well. The ODT should not be used with any moderate or strong CYP3A4 inhibitor.
Blood pressure and alpha-blockers
In men with ED, a single 20 mg dose lowered supine blood pressure by an average maximum of 7/8 mmHg compared with placebo, with the largest drop 1–4 hours after dosing.
Alpha-blockers, used for prostate enlargement, add to this effect. In label studies of healthy men aged 45–74, blood pressure fell sharply (standing systolic under 85 mmHg or a fall of more than 30 mmHg) in:
- 19 of 29 men on terazosin 10 mg;
- 9 of 24 men on tamsulosin 0.4 mg.
These outliers were more frequent when the two drugs peaked at the same time. The terazosin arm dosed for simultaneous peaks was stopped early. The label advises starting vardenafil only in men who are stable on an alpha-blocker, at 5 mg, and considering a time gap between the two doses.
Alcohol at about 0.5 g/kg did not add to vardenafil’s blood-pressure effect in healthy volunteers.
Heart conditions
Because sex itself carries some cardiac risk, the label says ED drugs should not be used by men for whom sexual activity is inadvisable. No controlled data exist in men with:
- unstable angina;
- resting systolic blood pressure under 90 mmHg;
- uncontrolled hypertension (over 170/110 mmHg);
- stroke, life-threatening arrhythmia or heart attack within the last 6 months;
- severe heart failure.
The label does not recommend vardenafil in these groups. Men with left ventricular outflow obstruction, such as aortic stenosis, may be sensitive to vasodilators. In two treadmill trials in men with stable angina, 10 mg and 20 mg did not change total exercise time or time to angina compared with placebo.
Vision and hearing
The label warns about these class effects:
- Vision. Non-arteritic anterior ischemic optic neuropathy (NAION), a sudden loss of blood flow to the optic nerve, has been reported rarely with all PDE5 inhibitors. Observational studies suggest about a 2-fold higher risk soon after use (risk estimate 2.15, 95% CI 1.06–4.34), but they do not prove cause and effect. Men who have had NAION before are at higher risk of recurrence. Vardenafil has not been studied in hereditary retinal disease such as retinitis pigmentosa.
- Hearing. Sudden decrease or loss of hearing, sometimes with tinnitus and dizziness, has been reported after PDE5 inhibitor use. It is not clear whether the drug causes it.
In both cases the label says to stop the drug and seek medical care right away.
Priapism and other events
The label lists these less common events:
- Priapism. Erections lasting over 4 hours have been reported rarely and need urgent treatment. Untreated priapism (a painful erection lasting over 6 hours) can cause permanent damage.
- Neurologic events. Seizure, seizure recurrence and transient global amnesia (a brief episode of memory loss) have been reported after marketing.
- Bleeding. Doses up to 20 mg did not prolong bleeding time, alone or with aspirin. The drug has not been given to men with bleeding disorders or active peptic ulcers.
- Other drugs. Vardenafil may inhibit P-glycoprotein, a drug transporter. Its effect on sensitive substrates such as dabigatran is unknown.
High doses
The largest single dose studied in humans was 120 mg in healthy men. Most of them had reversible back pain or muscle pain and “abnormal vision.” Single doses up to 80 mg, and 40 mg once daily for 4 weeks, caused no serious side effects. However, 40 mg twice daily caused cases of severe back pain.
Who should not use it
From the labels, vardenafil should not be used by men who:
- take nitrates or nitric oxide donors in any form;
- take a guanylate cyclase stimulator such as riociguat;
- have severe hepatic impairment (Child-Pugh C) or are on dialysis;
- have congenital QT prolongation or take class IA or III antiarrhythmics (label: “should avoid”);
- for the ODT only: take moderate or strong CYP3A4 inhibitors, have moderate hepatic impairment, have phenylketonuria (each tablet contains 1.01 mg phenylalanine from aspartame), or have hereditary fructose intolerance (the tablet contains sorbitol).
Use outside medicine
Vardenafil has been found hidden in supplements sold for sexual enhancement. An analysis of FDA warnings from 2007 to 2016 found vardenafil in 5 adulterated products, far fewer than the 166 sexual-enhancement products that contained sildenafil (Tucker et al., JAMA Netw Open 2018; PMC). Hidden doses are unknown, which matters given the nitrate and CYP3A4 interactions above.
PDE5 inhibitors, including vardenafil, are not listed on the WADA 2026 Prohibited List.
Key takeaways
- The brands are gone in the US, the drug is not. FDA withdrew the Levitra and Staxyn approvals as of July 3, 2024, at Bayer’s request, after finding they were not withdrawn for safety or effectiveness reasons. Generic tablets and ODTs remain.
- Short-acting like sildenafil. The half-life is about 4–5 hours, compared with about 4 hours for sildenafil and 17.5 hours for tadalafil.
- Clearly effective in trials. At 10–20 mg, about 64–65% of attempts led to successful intercourse, compared with 32% on placebo, in the main North American trial. Benefit was smaller after prostate surgery.
- The ODT is a different dose. The 10 mg orally disintegrating tablet gives higher exposure than the 10 mg tablet and is not interchangeable with it.
- Interactions are the main hazard. Nitrates and riociguat are contraindicated, ritonavir raised exposure 49-fold, and alpha-blockers can cause large blood-pressure drops.
- Small QT effect. QTc rose by about 8 ms at 10 mg, similar to moxifloxacin. Men with congenital long QT or on class IA/III antiarrhythmics should avoid it.
Sources
- Bayer HealthCare Pharmaceuticals. Levitra (vardenafil hydrochloride) tablets, prescribing information, revised 3/2023. FDA; Drugs@FDA, NDA 021400.
- Bayer HealthCare Pharmaceuticals. Staxyn (vardenafil hydrochloride) orally disintegrating tablets, prescribing information, revised 4/2023. FDA; Drugs@FDA, NDA 200179.
- Food and Drug Administration. Determination that Levitra (vardenafil hydrochloride) oral tablets, 5 milligrams, 10 milligrams, and 20 milligrams, were not withdrawn from sale for reasons of safety or effectiveness. Federal Register. May 3, 2023;88:27901 (FR Doc 2023-09365). Federal Register.
- Food and Drug Administration. Determination that NALFON (fenoprofen calcium) oral capsules, equivalent to 300 milligram base, and other drug products were not withdrawn from sale for reasons of safety or effectiveness. Federal Register. April 9, 2024;89:24841 (FR Doc 2024-07494). Federal Register.
- Food and Drug Administration. Pfizer, Inc., et al.; withdrawal of approval of 23 new drug applications. Federal Register. June 3, 2024;89:47566 (FR Doc 2024-12065). Federal Register.
- Generic vardenafil labels: Zydus Pharmaceuticals USA, vardenafil tablets; Alembic Pharmaceuticals, vardenafil hydrochloride orally disintegrating tablets. DailyMed (Zydus); DailyMed (Alembic).
- European Medicines Agency. Levitra (vardenafil): EPAR, marketing authorisation issued 6 March 2003. EMA.
- National Center for Biotechnology Information. Vardenafil, PubChem CID 135400189. PubChem.
- Pfizer / Viatris. Viagra (sildenafil citrate) tablets, prescribing information. DailyMed.
- Eli Lilly and Company. Cialis (tadalafil) tablets, prescribing information. DailyMed.
- Goldstein I, Young JM, Fischer J, et al. Vardenafil, a new phosphodiesterase type 5 inhibitor, in the treatment of erectile dysfunction in men with diabetes: a multicenter double-blind placebo-controlled fixed-dose study. Diabetes Care. 2003;26(3):777–783. PubMed.
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- Wang H, Guo B, Huang Z, et al. Vardenafil in the treatment of male erectile dysfunction: a systematic review and meta-analysis. Adv Ther. 2021;38(2):1301–1313. PubMed.
- Sperling H, Gittelman M, Norenberg C, et al. Efficacy and safety of an orodispersible vardenafil formulation for the treatment of erectile dysfunction in elderly men and those with underlying conditions: an integrated analysis of two pivotal trials. J Sex Med. 2011;8(1):261–271. PubMed.
- Rubio-Aurioles E, Porst H, Eardley I, et al. Comparing vardenafil and sildenafil in the treatment of men with erectile dysfunction and risk factors for cardiovascular disease: a randomized, double-blind, pooled crossover study. J Sex Med. 2006;3(6):1037–1049. PubMed.
- Jannini EA, Isidori AM, Gravina GL, et al. The ENDOTRIAL study: a spontaneous, open-label, randomized, multicenter, crossover study on the efficacy of sildenafil, tadalafil, and vardenafil in the treatment of erectile dysfunction. J Sex Med. 2009;6(9):2547–2560. PubMed.
- Yuan J, Zhang R, Yang Z, et al. Comparative effectiveness and safety of oral phosphodiesterase type 5 inhibitors for erectile dysfunction: a systematic review and network meta-analysis. Eur Urol. 2013;63(5):902–912. PubMed.
- Chen L, Staubli SE, Schneider MP, et al. Phosphodiesterase 5 inhibitors for the treatment of erectile dysfunction: a trade-off network meta-analysis. Eur Urol. 2015;68(4):674–680. PubMed.
- Salonia A, Bettocchi C, Burnett A, et al. A comparative evaluation of on-demand phosphodiesterase-5 inhibitor efficacy in erectile dysfunction treatment: a systematic review and network meta-analysis of double-blind, placebo-controlled, randomized trials. J Sex Med. 2026;23(7):qdag176. PubMed.
- Morganroth J, Ilson BE, Shaddinger BC, et al. Evaluation of vardenafil and sildenafil on cardiac repolarization. Am J Cardiol. 2004;93(11):1378–1383. PubMed.
- Tucker J, Fischer T, Upjohn L, et al. Unapproved pharmaceutical ingredients included in dietary supplements associated with US Food and Drug Administration warnings. JAMA Netw Open. 2018;1(6):e183337. PubMed; PMC.
- World Anti-Doping Agency. World Anti-Doping Code International Standard: Prohibited List 2026. WADA 2026 Prohibited List.