PDE5 Inhibitors
Sildenafil, tadalafil, vardenafil and avanafil are approved for erectile dysfunction (ED); tadalafil also treats the signs and symptoms of BPH. This page describes their urologic use. Pulmonary-hypertension products and regimens have different indications and dosing and should not be added to an ED prescription.[1][2][3][4]
PDE5 inhibition slows breakdown of cyclic GMP generated through nitric oxide signaling, promoting cavernosal smooth-muscle relaxation. Sexual stimulation is still required. Drug exposure, response and adverse effects vary; duration of activity means an opportunity to respond, not a continuous erection.[1][2]
For alternative treatments see Intracavernosal injection agents and Intraurethral alprostadil. Treatment decisions and cardiovascular assessment are also discussed under Erectile dysfunction.
US doses and practical differences
The table describes standard adult ED dosing before adjustments for interactions or organ impairment.[1][2][3][4]
| Agent | Usual starting regimen | Adjustment and timing | Practical distinction |
|---|---|---|---|
| Sildenafil | 50 mg as needed | 25–100 mg; approximately one hour before sex, permissible window 30 minutes to four hours beforehand; no more than once daily | A high-fat meal can delay absorption; choose lower initial doses in the situations below |
| Tadalafil, as needed | 10 mg | Decrease to 5 mg or increase to 20 mg; no more than once daily in most patients | Effect may persist up to 36 hours; food does not meaningfully alter dosing |
| Tadalafil, daily ED | 2.5 mg at roughly the same time each day | Increase to 5 mg if appropriate | Daily BPH or ED/BPH regimen is ordinarily 5 mg, subject to renal and interaction limits |
| Vardenafil, film-coated tablet | 10 mg | Adjust to 5–20 mg; about 60 minutes before sex; no more than once daily | QT precautions; lower doses are needed with selected interactions. Orally disintegrating products have their own label and are not automatically interchangeable |
| Avanafil | 100 mg as needed | 100 or 200 mg as early as about 15 minutes before sex; 50 mg approximately 30 minutes beforehand; no more than once daily | Strong CYP3A4 inhibitors preclude use; moderate inhibitors limit the dose |
No drug is universally the most effective or best tolerated. Cross-trial rankings depend on dose, population, endpoint and indirect comparisons. Choose according to timing preference, previous response, cost/access and adverse effects, then reassess.[5]
Before calling treatment unsuccessful
Confirm correct drug, dose, timing, sexual stimulation and repeated opportunities to use it. A large meal can delay sildenafil, vardenafil and avanafil absorption. Discuss anxiety, relationship factors, underlying vascular or neurological disease and medication contributors. Titrate within the product's limits; changing agents or daily versus as-needed tadalafil may be reasonable, but a fixed number of maximal-dose attempts with every agent is not an AUA requirement before offering another treatment.[5][6]
Assess suspected testosterone deficiency appropriately. Testosterone may help selected men with confirmed symptomatic deficiency; it is not an automatic rescue treatment for every PDE5 nonresponse or a requirement before discussing injections or devices. See Testosterone replacement.[5][6]
Safety checks that change prescribing
Do not combine PDE5 inhibitors with organic nitrates/nitrites, including recreational “poppers,” or guanylate-cyclase stimulators such as riociguat. The interaction can cause severe hypotension. If chest pain occurs after a PDE5 inhibitor, seek emergency care and disclose the agent and last dose; do not self-administer a nitrate.[1][2][3][4]
Timing does not turn this into a routine combination. Princeton IV advises avoiding nitrates for at least 24 hours after sildenafil, vardenafil or avanafil, and 48 hours after tadalafil. The US sildenafil and vardenafil labels do not establish a universally safe nitrate interval. Tadalafil and avanafil labels allow consideration in a life-threatening situation only after at least 48 and 12 hours, respectively, with close medical supervision and hemodynamic monitoring. Delayed clearance and the clinical situation still matter; the avanafil label's emergency provision differs from the more conservative Princeton consensus interval.[1][2][3][4][7]
| Issue | Prescribing implication |
|---|---|
| Cardiovascular fitness | Defer ED drug treatment when sexual activity is medically inadvisable. Unstable angina, recent cardiovascular events, marked hypotension or uncontrolled hypertension require appropriate assessment; exact excluded populations differ by label |
| Alpha-blockers and other antihypertensives | Additive hypotension is possible. For ED combination treatment, establish stability on the alpha-blocker and start the PDE5 inhibitor at its lowest recommended dose; volume depletion increases risk |
| Vardenafil and QT | Avoid with congenital QT prolongation or class IA/III antiarrhythmics; review other QT-prolonging medication |
| Prior NAION | US labels call for caution and an individualized benefit–risk assessment, rather than classifying every prior event as a uniform absolute contraindication. Ophthalmology input may be appropriate |
| Retinitis pigmentosa | Sildenafil label advises caution because data are lacking; tadalafil, vardenafil and avanafil labels do not recommend use in inherited degenerative retinal disease. Do not generalize one product's wording to the entire class |
| Sudden visual or hearing loss | Stop the drug and obtain urgent assessment |
| Prolonged erection | An erection persisting four hours requires urgent care, regardless of whether it is painful |
| Common adverse effects | Headache, flushing, dyspepsia and congestion; sildenafil can cause transient color-vision changes, and tadalafil can cause back pain/myalgia |
| Alcohol | Substantial intake can worsen orthostasis and sexual performance; an absorption-delay claim is not the main counseling point |
These are selected label precautions, not a substitute for the complete product-specific contraindications and interactions.[1][2][3][4]
Renal, hepatic and interaction adjustments
| Agent | Selected high-yield US label limits |
|---|---|
| Sildenafil | Consider 25 mg initially with age over 65, hepatic impairment, CrCl below 30 mL/min or strong CYP3A4 inhibition. With ritonavir, maximum 25 mg in 48 hours. With stable alpha-blocker therapy, start 25 mg |
| Tadalafil, as needed | CrCl 30–50: start 5 mg, maximum 10 mg in 48 hours. CrCl below 30 or dialysis: maximum 5 mg in 72 hours. Potent CYP3A4 inhibitor: maximum 10 mg in 72 hours |
| Tadalafil, daily | Not recommended with CrCl below 30 or dialysis. For BPH/ED-BPH with CrCl 30–50, start 2.5 mg, consider 5 mg according to response. Potent CYP3A4 inhibitor: maximum 2.5 mg daily, which does not provide the standard BPH dose |
| Tadalafil and liver disease | As-needed dosing in Child-Pugh A/B should not exceed 10 mg; daily use requires caution because evidence is limited. Not recommended in Child-Pugh C |
| Vardenafil tablets | Consider 5 mg initially at age 65 or older. Child-Pugh B: start 5 mg, maximum 10 mg; do not use with Child-Pugh C or dialysis. Ritonavir/cobicistat: maximum 2.5 mg in 72 hours; other inhibitor-specific dose limits also apply |
| Avanafil | Do not use with strong CYP3A4 inhibitors; with moderate inhibitors, maximum 50 mg in 24 hours. Start 50 mg with stable alpha-blocker treatment. Do not use in severe renal disease/dialysis or severe hepatic impairment |
Check all concurrent restrictions; a permissible dose under one condition does not override another contraindication.[1][2][3][4]
Routine stacking of PDE5 inhibitors is not supported by US labeling. Specialist off-label combinations described in guidelines require explicit planning and monitoring; patients should not add sildenafil to daily tadalafil on their own.[1][2][5]
LUTS/BPH: benefit and combination treatment
AUA 2026 recommends offering tadalafil 5 mg daily for LUTS/BPH with or without ED (moderate recommendation, Grade B). Symptom improvement is modest on average. In the 2018 Cochrane review, the placebo-adjusted IPSS difference was 1.89 points lower (95% CI 1.50–2.27 lower; 4,293 participants; low-certainty evidence, six to 12 weeks). An approximately five- or six-point within-group improvement must not be presented as a five- or six-point advantage over placebo.[8][9]
Tadalafil is a symptom treatment; it has not established the prostate-shrinking or long-term retention/surgery-prevention effects of 5-alpha-reductase inhibitors.[8][9]
| Combination | Evidence and label distinction |
|---|---|
| Tadalafil + uroselective alpha-blocker | AUA 2026 permits this conditionally (Grade C), with generally small additional symptom benefits and monitoring for hypotension. The US CIALIS label still does not recommend the combination for BPH. This is a guideline–label difference that should be discussed when selecting treatment |
| Tadalafil + 5-ARI | AUA 2026 permits this conditionally for LUTS/BPH with estimated prostate volume over 30 cc and/or PSA over 1.5 ng/mL. The CIALIS label describes initiation with finasteride for up to 26 weeks; incremental benefit beyond that period is unknown |
The label's instruction to stop an alpha-blocker at least a day before starting daily CIALIS for BPH describes switching away from the alpha-blocker. It is not a one-day pause that makes subsequent combination dosing label-concordant.[2][8]
See Alpha-blockers and 5-alpha-reductase inhibitors for agent selection and progression prevention.
After radical prostatectomy: treatment versus rehabilitation
Offer treatment for postoperative ED and support resumption of sexual activity. An erection improved while taking medication is different from recovery of unassisted function after medication stops. A fixed nightly regimen should not be promised to prevent fibrosis or restore spontaneous erections.[5][10]
- REACTT: 423 men with normal preoperative function undergoing bilateral nerve-sparing prostatectomy were randomized to tadalafil 5 mg daily, 20 mg on demand or placebo for nine months. After six weeks off treatment, IIEF-EF at least 22 occurred in 20.9%, 16.9% and 19.1%, respectively; neither tadalafil comparison was significant. Daily tadalafil improved drug-assisted outcomes and reduced measured length loss by a mean 4.1 mm versus placebo during treatment, but did not improve the primary unassisted-function endpoint.[11]
- Cochrane 2018: eight randomized trials with 1,699 participants provided mostly very-low-certainty evidence. Scheduled PDE5 therapy did not establish better recovery than on-demand treatment.[10]
- 2021 network meta-analysis: a positive signal for regular sildenafil 100 mg came from comparisons across 22 studies/2,711 patients, with wide uncertainty and incomplete adverse-event reporting. This supports further investigation, not a universal high-dose nightly prescription or an 80% spontaneous-recovery guarantee.[12]
Choose daily or on-demand treatment according to the patient's goals, response and tolerability. Escalation to vacuum support, urethral therapy or injections can assist sexual activity; the best regimen for restoring unassisted function remains uncertain.[5][10]
Recurrent ischemic priapism: preventive use remains uncertain
A PDE5 inhibitor may be considered off label under specialist supervision, started when the penis is flaccid, for selected recurrent ischemic priapism. It is not treatment for an acute ischemic episode, and tadalafil 5 mg each morning is not an established universal default.[13]
The early sildenafil randomized trial enrolled only 13 patients with sickle cell disease and did not show a significant blinded primary benefit. More recently, the 2025 PIN phase 2 feasibility trial randomized 64 men with sickle cell anemia to hydroxyurea plus tadalafil or hydroxyurea plus placebo. Over a median ten months, it demonstrated feasibility but no significant additional reduction in priapism with tadalafil. Improvements within each arm from the pretreatment period do not prove tadalafil efficacy. The trial's limited size also does not establish equivalence.[14][15]
See Priapism management for acute treatment and individualized recurrence prevention.
Other urologic uses
| Setting | Appropriate interpretation |
|---|---|
| Peyronie's disease | Treat accompanying ED when appropriate. Antifibrotic laboratory findings and a retrospective tadalafil cohort do not establish correction of curvature. See Peyronie's agents |
| Premature ejaculation | Off-label in the US. EAU 2026 allows PDE5 inhibitors alone or with other treatment, including in men without ED; treat coexisting ED first. Evidence for latency, confidence and satisfaction differs, so do not promise a uniform effect. Regulatory approval of dapoxetine or topical spray elsewhere is not FDA approval |
| Ureteral stone passage | PDE5-containing combinations have trial signals, but the EAU's explicit first-line MET recommendation is an alpha-blocker for selected conservatively managed distal stones 5–10 mm. Do not promote a network ranking into a routine tadalafil regimen |
| Female sexual dysfunction | Not a US-approved indication for these ED products. Investigational or selected off-label evidence should not be generalized into routine treatment of female interest/arousal problems |
| Renal protection | Not an approved or established clinical indication; preclinical ischemia models do not justify prophylactic prescribing |
These distinctions are supported by the relevant labels, current EAU sections and selected primary evidence.[1][2][16][17][18]
Kidney transplantation
ED treatment after transplantation requires renal-function, blood-pressure and interaction review. A ten-patient sildenafil study found increased sildenafil exposure and marked blood-pressure reductions compared with historical healthy controls; it could not separate tacrolimus, other medication and underlying disease as causes. A subsequent nine-patient study of sildenafil 25 mg daily for nine days did not materially change tacrolimus exposure, but again lowered blood pressure. Neither study establishes a blanket contraindication to daily tadalafil in every tacrolimus recipient. Choose agent and dose with the transplant team according to the actual regimen and organ function.[19][20]
References
1. Pfizer. VIAGRA US prescribing information. Label.
2. Eli Lilly. CIALIS US prescribing information. DailyMed.
3. Vardenafil hydrochloride film-coated tablets: US prescribing information. DailyMed.
4. STENDRA US prescribing information. DailyMed.
5. EAU. Sexual and Reproductive Health: Management of Erectile Dysfunction. 2026. Guideline.
6. Burnett AL, et al. Erectile Dysfunction: AUA Guideline. J Urol. 2018. doi:10.1016/j.juro.2018.05.004.
7. Kloner RA, et al. Princeton IV consensus guidelines: PDE5 inhibitors and cardiac health. J Sex Med. 2024;21:90–116. doi:10.1093/jsxmed/qdad163.
8. Goueli R, et al. Management of Lower Urinary Tract Symptoms Attributed to Benign Prostatic Hyperplasia: AUA Guideline (2026) Part II: Medical Management. J Urol. 2026;216:152–160. doi:10.1097/JU.0000000000005098.
9. Pattanaik S, et al. Phosphodiesterase inhibitors for lower urinary tract symptoms consistent with benign prostatic hyperplasia. Cochrane Database Syst Rev. 2018;CD010060. doi:10.1002/14651858.CD010060.pub2.
10. Philippou YA, et al. Penile rehabilitation for postprostatectomy erectile dysfunction. Cochrane Database Syst Rev. 2018;CD012414. doi:10.1002/14651858.CD012414.pub2.
11. Montorsi F, et al. Effects of tadalafil treatment on erectile function recovery following bilateral nerve-sparing radical prostatectomy: a randomised placebo-controlled study (REACTT). Eur Urol. 2014;65:587–596. doi:10.1016/j.eururo.2013.09.051.
12. Sari Motlagh R, et al. Penile Rehabilitation Strategy after Nerve Sparing Radical Prostatectomy: A Systematic Review and Network Meta-Analysis of Randomized Trials. J Urol. 2021;205:1018–1030. doi:10.1097/JU.0000000000001584.
13. EAU. Sexual and Reproductive Health: Priapism. 2026. Guideline.
14. Burnett AL, et al. Randomized controlled trial of sildenafil for preventing recurrent ischemic priapism in sickle cell disease. Am J Med. 2014;127:664–668. doi:10.1016/j.amjmed.2014.03.019.
15. Idris IM, et al. A controlled trial for preventing priapism in sickle cell anemia: hydroxyurea plus placebo vs hydroxyurea plus tadalafil. Blood. 2025;145:3101–3112. doi:10.1182/blood.2024027898.
16. Spirito L, et al. Daily low-dose tadalafil may reduce the penile curvature progression rate in patients with acute Peyronie's disease: a retrospective comparative analysis. Int J Impot Res. 2024;36:129–134. doi:10.1038/s41443-022-00651-8.
17. EAU. Sexual and Reproductive Health: Disorders of Ejaculation. 2026. Guideline.
18. EAU. Urolithiasis: Guidelines. 2026. Guideline.
19. Christ B, et al. Interactions of sildenafil and tacrolimus in men with erectile dysfunction after kidney transplantation. Urology. 2001;58:589–593. doi:10.1016/S0090-4295(01)01306-1.
20. Christ B, et al. Investigation on interaction between tacrolimus and sildenafil in kidney-transplanted patients with erectile dysfunction. Int J Clin Pharmacol Ther. 2004;42:149–156. doi:10.5414/CPP42149.