Tadalafil is a prescription PDE5 inhibitor sold as brand Cialis and as generic tablets. The FDA has approved it for erectile dysfunction (ED), for the urinary symptoms of benign prostatic hyperplasia (BPH), and for both together.1,2 It works only with sexual stimulation, and its label reports better erectile function than placebo for up to 36 hours after a dose.1 It must never be combined with any nitrate, including nitrate heart medicines and recreational "poppers". Your prescriber sets the dose and schedule from your health history, medications and goals.
What Tadalafil Treats
Tadalafil carries three FDA-approved uses on its label: ED, the signs and symptoms of BPH, and ED with BPH at the same time.1 The generic tablets list the same three indications.2 BPH is a noncancerous enlargement of the prostate.
The label adds one limit. When tadalafil is started together with finasteride for BPH, that pairing is recommended for up to 26 weeks, because the extra benefit from tadalafil shrinks over that time.1 If you already take finasteride for your prostate or for hair, tell your prescriber.
Tadalafil belongs to the PDE5 inhibitor class, which also includes sildenafil. The American Urological Association (AUA) guideline asks clinicians to inform every man of all treatments that are not contraindicated and to choose through shared decision-making.7 Tadalafil is often one of those options, and you have a say in which one you start with. If cost is part of the decision, ED medication cost compares brand and generic pricing.
How Tadalafil Works in the Body
An erection starts when sexual stimulation releases nitric oxide in the penis. Nitric oxide raises a messenger molecule called cyclic GMP (cGMP), which relaxes smooth muscle and lets blood flow into the erectile tissue.1 PDE5 is the enzyme that breaks cGMP down.
Tadalafil blocks PDE5, so cGMP lasts longer and the erection is easier to reach and keep.1 Because the process begins with nitric oxide released during arousal, tadalafil has no effect without sexual stimulation.1 The drug does not create desire. It supports the blood flow response once you are aroused.
The same cGMP effect appears in the smooth muscle of the prostate, the bladder and their blood supply. The label states that the mechanism for reducing BPH symptoms has not been established.1 In laboratory studies, tadalafil was more than 10,000-fold more potent for PDE5 than for several other PDE enzymes found in the heart, brain and blood vessels.1 Your prescriber still screens your medicines for interactions before prescribing it.
How Long Tadalafil Lasts
Tadalafil's effect window is long. Taken as needed, it improved erectile function compared with placebo for up to 36 hours after a dose.1 Its mean terminal half-life, the time for blood levels to fall by half, is 17.5 hours in healthy men.1 The label states it may be taken without regard to food.1
The label describes two ways to use it: as needed before sex, or once daily without regard to the timing of sex.1 Your prescriber chooses between them, and the amount, based on your response and side effects.
The evidence on which schedule works better is modest. A meta-analysis of eight studies found that men taking tadalafil daily for 12 weeks scored an average of 1.82 points higher on the erectile function domain than men taking it on demand.5 The authors noted that a gap of that size may not matter clinically.5 An overview of 23 systematic reviews reported that low-dose daily tadalafil may be more effective than high-dose on-demand tadalafil.6 If you want spontaneity, or you also have urinary symptoms, raise that, because those are the factors your prescriber weighs when picking a schedule. For how tadalafil compares with sildenafil on timing and effect, see sildenafil vs tadalafil.
What the Trials Found for ED and BPH
Tadalafil was given to more than 9,000 men in clinical trials worldwide.1 A pooled analysis of 11 double-blind, placebo-controlled trials covered 2,102 men with a broad range of ED causes. It included men with diabetes, high blood pressure, cardiovascular disease, high cholesterol, depression and BPH.3
Tadalafil improved erectile function in every subgroup analyzed.3 At the higher of the two doses studied, the share of men reporting improved erections ranged from 72% to 91% across subgroups, compared with 20% to 47% on placebo.3 Those figures come from a global assessment question, so they describe how men rated their erections rather than a cure rate.
For urinary symptoms, a meta-analysis of 13 randomized trials with 3,973 men found once-daily tadalafil improved both BPH-related urinary symptoms and ED over 12 weeks.4 If you have both problems, one daily medicine may cover both, and your prescriber can tell you whether that applies to you.
Before tadalafil is started for BPH, the label asks prescribers to consider other urinary conditions that cause similar symptoms. It also notes that prostate cancer and BPH may coexist.1 That is why your urinary symptoms get their own evaluation before a prescription.
Common Side Effects of Tadalafil
The most common side effects on the label are headache, indigestion (dyspepsia), back pain, muscle aches, nasal congestion, flushing and limb pain.1 In the as-needed ED trials, headache occurred in 11% to 15% of men on tadalafil compared with 5% on placebo. Indigestion occurred in 4% to 10% compared with 1%, and back pain in 3% to 6% compared with 3%.1
Few men stopped because of side effects. In those trials, 3.1% of men on tadalafil stopped because of adverse events, compared with 1.4% on placebo.1
Back pain has a typical pattern. In clinical pharmacology trials, back pain or muscle aches usually began 12 to 24 hours after a dose and resolved within 48 hours. The pain was generally mild or moderate and resolved without treatment.1 Testing for inflammation, muscle injury and kidney damage found no underlying disease.1 If the pain is severe or keeps returning, tell your prescriber, who can review the dose or the drug.
Three serious reactions need prompt action. The label tells patients to seek emergency treatment if an erection lasts more than 4 hours.1 It also says to stop tadalafil and get medical care for a sudden loss of vision in one or both eyes, or a sudden decrease or loss of hearing.1 If any of those happen to you, treat them as urgent.
Drug Interactions and Medical Screening
Nitrates are the best-known combination the label forbids outright, and guanylate cyclase stimulators such as riociguat are the other. Tadalafil strengthens the blood-pressure-lowering effect of any organic nitrate, so the combination is contraindicated.1 If you have taken tadalafil and develop chest pain, tell emergency staff, because the label says at least 48 hours should pass before nitrates are considered, and only under close supervision.1
The label lists several other interactions your prescriber screens for:
- Riociguat and other guanylate cyclase stimulators, which must not be combined with tadalafil.1
- Alpha-blockers and blood pressure medicines, which can add to the drop in blood pressure. The label does not recommend tadalafil with an alpha-blocker for BPH treatment.1
- Alcohol in substantial amounts, which the label defines as 5 units or more and which can lower blood pressure when combined with tadalafil.1
- CYP3A4 inhibitors such as ketoconazole tablets and ritonavir, which raise tadalafil levels, and erythromycin, itraconazole and grapefruit juice, which likely do the same.1
- CYP3A4 inducers such as rifampin, carbamazepine and phenytoin, which lower tadalafil levels and can be expected to reduce its effect.1
Your heart health is part of the screen too. The label states that tadalafil should not be used if sex is inadvisable because of cardiovascular status.1 Bring your full medication list, including supplements, to the visit where tadalafil is discussed.
How a Prescriber Improves Your Response to Tadalafil
A poor response has causes your prescriber can look for:
- No sexual stimulation. Without it, tadalafil has no effect.1
- An untreated cause. The label calls for a medical assessment to identify underlying causes before treatment.1 Low testosterone is one cause worth measuring. An overview of systematic reviews found that men with ED and hypogonadism (low testosterone) seemed to improve further when testosterone was added to a PDE5 inhibitor.6
- An interacting medicine. CYP3A4 inducers such as rifampin can lower tadalafil exposure and blunt its effect.1
If you are under 40, ED in young men covers the causes that are more common at that age. If you have been looking at supplements instead, natural PDE5 inhibitors reviews that evidence. Whatever the reason, report what happened to your prescriber, who can adjust the plan or look for the cause.
The Opt Take on Tadalafil
Tadalafil helps blood flow, and the reason your blood flow needed help is the larger question. The tadalafil trials included men with diabetes, high blood pressure, high cholesterol and heart disease alongside ED.3 A pill that works does not show which of those conditions is behind your ED. Your labs can show the blood sugar, cholesterol and hormone markers behind several of them.
At Opt Health, every lab we order gets read by a physician before anyone is offered a treatment. Your initial panel covers 55+ biomarkers, including hormones, inflammation and cardiovascular risk, followed by a 1:1 consultation with an Opt Health physician who reviews your existing conditions and current medications. If your plan includes tadalafil or another prescription, it ships from our pharmacy to your door.
Labs and a physician consultation repeat every 3 to 4 months. Your physician compares the new numbers with your baseline, asks how the medicine is working and what side effects you notice, and adjusts the plan on what changed.
Get started: Begin with Opt Health, where a physician reads your labs, builds your plan, and adjusts it over the loop.
Frequently Asked Questions
In 11 pooled placebo-controlled trials, tadalafil improved erectile function in every subgroup studied, including men with diabetes, heart disease and depression.3 At the higher of the two doses studied, the share of men reporting improved erections ranged from 72% to 91% across subgroups, compared with 20% to 47% on placebo.3 Your own response depends on the cause of your ED, which is why your prescriber looks for it.
Tadalafil raises cGMP in the smooth muscle of the prostate, the bladder and their blood supply, the same pathway it acts on in the penis.1 The label states that the exact mechanism for easing BPH symptoms has not been established.1 Once-daily use improved urinary symptoms and ED over 12 weeks in a meta-analysis of 13 trials.4 Your prostate symptoms should be evaluated first, since other conditions can look the same.
The common reasons are missing sexual stimulation, an untreated underlying cause, and interacting medicines that lower tadalafil levels.1 Low testosterone is one cause worth testing, since adding testosterone in men with hypogonadism seemed to improve results further.6 Tell your prescriber how and when you took it, so the dose, schedule or diagnosis can be reviewed. Injections such as trimix are another option your prescriber can weigh when tablets do not work for you.
The label does not give a mechanism. It reports that back pain and muscle aches usually started 12 to 24 hours after a dose and resolved within 48 hours.1 Testing in those men found no inflammation, muscle injury or kidney damage.1 If back pain is bothering you, your prescriber can review the dose or try a different medicine.
The label describes PDE5 inhibitors, including tadalafil, as mild systemic vasodilators, meaning they widen blood vessels throughout the body.1 Headache was the most common side effect in the as-needed trials, at 11% to 15% compared with 5% on placebo.1 Let your prescriber know if your headaches are frequent or severe.
Tadalafil has not been shown to be better than sildenafil overall. Tadalafil lasts longer, with improved erectile function for up to 36 hours after a dose.1 An overview of systematic reviews found that the evidence comparing different PDE5 inhibitors directly is low.6 The right choice depends on your schedule, side effects and health, and sildenafil vs tadalafil lays out those differences.
The right ED prescription starts with knowing why erections changed. An Opt Health membership pairs a 55+ biomarker panel with a 1:1 physician review, then repeats labs and a physician consultation every 3 to 4 months.
References
- Eli Lilly and Company. CIALIS (tadalafil) tablets, US prescribing information. DailyMed. Published June 10, 2026. Accessed October 14, 2026. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895
- Teva Pharmaceuticals, Inc. Tadalafil tablets, US prescribing information. DailyMed. Published September 2, 2026. Accessed October 14, 2026. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3ad14d63-42e7-493f-b56c-e02a4fd139f7
- Lewis RW et al. The efficacy of tadalafil in clinical populations. J Sex Med. 2005;2(4):517-31. https://pubmed.ncbi.nlm.nih.gov/16422847/
- Wang Y et al. Tadalafil 5 mg once daily improves lower urinary tract symptoms and erectile dysfunction: a systematic review and meta-analysis. Low Urin Tract Symptoms. 2018;10(1):84-92. https://pubmed.ncbi.nlm.nih.gov/29341503/
- Bansal UK et al. The efficacy of tadalafil daily vs on demand in the treatment of erectile dysfunction: a systematic review and meta-analysis. Urology. 2018;112:6-11. https://pubmed.ncbi.nlm.nih.gov/28882778/
- Pyrgidis N et al. The effect of phosphodiesterase-type 5 inhibitors on erectile function: an overview of systematic reviews. Front Pharmacol. 2021;12:735708. https://pubmed.ncbi.nlm.nih.gov/34557099/
- Burnett AL et al. Erectile dysfunction: AUA guideline. J Urol. 2018;200(3):633-641. https://pubmed.ncbi.nlm.nih.gov/29746858/
This content is for informational purposes and does not replace evaluation, diagnosis, or treatment by a qualified medical professional.
This article is part of our guide to erectile dysfunction. See how Opt Health treats ED at the root cause.
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