How Tadalafil Treats Erectile Dysfunction

Zuletzt aktualisiert: August 29, 2026

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Men’s sexual health is taken more seriously today than it once was, and rightly so — a satisfying sexual life is part of general wellbeing, not separate from it. This article covers tadalafil, one of the oral tablets used to treat erectile dysfunction, and what you should know before taking it.

Before Anything Else: Three Things That Need an Emergency Department

Tadalafil is a well-tolerated drug and most men take it without difficulty. Three situations are different, and none of them should wait until morning. In Thailand, call 1669.

• An erection lasting more than four hours, or one that is painful. This is priapism. Trapped blood loses its oxygen, and after a number of hours the erectile tissue begins to be permanently damaged — which is why the outcome depends almost entirely on how quickly it is treated. It is uncommon with tadalafil, but it is the reason this warning exists. Do not wait to see whether it settles, and do not feel embarrassed about presenting. Say plainly at the desk that you have had an erection for more than four hours; it is understood as an emergency.
• Sudden loss or blurring of vision, in one eye or both. Stop the tablet and be seen the same day. This is different from the mild, temporary colour or brightness changes some men notice.
• Sudden loss of hearing, or ringing in the ears with dizziness. Stop the tablet and be seen the same day.

Chest pain during sex is its own emergency, and it carries an additional instruction: tell the emergency team that you have taken tadalafil and when. That single sentence changes what they can safely give you, and it is covered in more detail below.

Modern erectile dysfunction treatment began in 1998, when Pfizer introduced the first oral PDE5 inhibitor, sildenafil (Viagra). Once it was in wide use, two limitations became clear: a short duration of action of roughly 3 to 5 hours, and side effects such as facial flushing and visual disturbance. Tadalafil was developed in response and approved by the US Food and Drug Administration in 2003.

How tadalafil works

• It acts on the erectile tissue inside the penis.
• It preserves the effect of nitric oxide, the key signalling molecule involved in erection.
• When sexual arousal occurs, the signal travels from the brain through the spinal cord to the penile tissue. Because tadalafil has primed that tissue, an erection is achieved more easily and maintained more reliably.

An important point: tadalafil does not create sexual desire. It has no effect on libido at all. What it does is make the erectile response work properly once you are already aroused. If low desire rather than erectile failure is the problem, tadalafil is not the answer, and the cause — low testosterone, medication side effects, depression, relationship factors — needs to be looked for. A short questionnaire helps to separate the two: see the IIEF-5 assessment.

What distinguishes tadalafil

1. It works for most men who try it — but how well depends heavily on why the erections stopped working. Response is good in the general population. It is substantially lower after radical prostatectomy, where PDE5 inhibitors clearly beat placebo but many men still need continued treatment and only a minority return to how things were before surgery, and lower again in long-standing diabetes. An earlier version of this page gave a single response figure across all men; that was more precise than the evidence allows, and the honest answer is that your own likelihood depends on the cause.
2. Up to 36 hours of effect — substantially longer than the other PDE5 inhibitors, which is why it is often the preferred choice when spontaneity matters. Note what that does nicht mean: it is not 36 hours of erection, and it does not mean a second dose within that window is safe.
3. It is not blocked by a fatty meal, unlike sildenafil.
4. It comes in two dosing patterns. A higher dose taken as needed before sex, or a low dose taken every day, which suits men who prefer not to plan around a tablet. The daily low dose is also licensed for the urinary symptoms of an enlarged prostate, so for some men one tablet addresses both — but if you already take a prostate tablet, read the interaction section below before assuming they simply combine.

On alcohol. An earlier version of this article said simply that tadalafil can be taken with alcohol. That is true of its effectiveness, and it is a real advantage over sildenafil. It is not the whole story: alcohol and tadalafil both widen blood vessels, so a substantial amount of drink alongside the tablet can leave you light-headed, particularly on standing. A drink or two is not a problem for most men. A heavy evening is a different proposition, and alcohol in quantity works against an erection anyway.

Nebenwirkungen

The common side effects are headache, indigestion, back pain, muscle aches, flushing and a blocked nose. They are generally mild and settle on their own, and how often they occur depends on the dose — which is one reason the daily low dose suits some men better than the as-needed higher dose. Approximate rates from the product labelling:

	As needed, higher dose	As needed, lower dose	Low dose, daily
Headache	15%	11%	4–6%
Indigestion	10%	8%	2–5%
Back pain	6%	5%	2–3%
Muscle ache	3%	4%	1–2%
Flushing	3%	3%	1–3%
Blocked nose	3%	3%	2–4%

Back and muscle ache is more characteristic of tadalafil than of the other drugs in the class. It is typically self-limited and eases without treatment; simple painkillers help, and it is not a reason to stop unless it is severe or persistent. An earlier version of this page described a specific timing for its onset and resolution — that detail was not something I could source, and it has been removed.

Who must not take it, and what must not be combined with it

• Nitrates — absolutely not, and the timing matters. Nitrates include sublingual tablets or spray for chest pain, isosorbide taken regularly, and nitrate infusions given in hospital. Both nitrates and tadalafil relax blood vessels through the same pathway, and together they can drop blood pressure catastrophically. Because tadalafil is long-acting, a nitrate should not be given within 48 hours of a dose — compared with about 24 hours for sildenafil and vardenafil, and about 12 for avanafil. That difference is about how long each drug lasts, not about which country you are in. This is precisely why an emergency team needs to know you have taken it: with that information they can treat your chest pain safely by another route.
• Amyl nitrite and related recreational inhalants, sold as poppers, are nitrates too. The same absolute prohibition applies, and this combination is a well-recognised cause of collapse.
• Riociguat and similar drugs for pulmonary hypertension must not be combined with it.
• Recent cardiac or neurological events. Tadalafil is avoided after a recent heart attack or stroke, in unstable angina, in uncontrolled blood pressure at either extreme, and in severe or unstable heart failure. What counts as recent, and whether your heart can safely take the exertion of sex at all, is a judgement for your doctor rather than a fixed number.
• Drugs that raise tadalafil levels — some antifungals, some HIV medicines, some antibiotics such as clarithromycin, and grapefruit juice in quantity. The dose usually needs reducing, so give a full medication list rather than only the prescriptions you think are relevant.
• Significant kidney or liver impairment, and a known allergy to the drug.

Prostate tablets: where the label and the guideline disagree

Alpha-blockers — tamsulosin, silodosin, alfuzosin, doxazosin — are the commonest tablets prescribed for an enlarged prostate, and a great many men who want tadalafil are already taking one. This deserves a section of its own, because the picture is genuinely unsettled and an earlier version of this page presented only one side of it.

The underlying issue is simple: both drugs lower blood pressure, so together they can make you feel faint, particularly on standing.

Where they are used together for erectile dysfunction, the product labelling advises that you should be stable on the alpha-blocker first, and that the PDE5 inhibitor is then started at the lowest dose. That is a caution, not a prohibition, and many men take both perfectly well.

Where the daily low dose is being used to treat the prostate itself, the two sources part company. The product labelling does nicht recommend combining daily tadalafil with an alpha-blocker for that purpose, and advises stopping the alpha-blocker at least a day before starting. The 2026 American Urological Association guideline, by contrast, gives a conditional recommendation that daily tadalafil can be combined with a uroselective alpha-blocker, noting a small additional symptom benefit alongside the risk of low blood pressure.

I would rather set that out than pick a side quietly. It means the combination is a legitimate clinical decision rather than a routine one, and it is a conversation to have specifically. What matters practically: tell whoever prescribes the tadalafil that you take a prostate tablet, and tell whoever manages your prostate that you are taking tadalafil. Feeling faint or light-headed on standing is the symptom to report. The prostate options themselves are covered in the two classes of BPH medication.

Men with sickle cell disease, myeloma or leukaemia, or an anatomically unusual penis, carry a higher risk of priapism and should be assessed before starting.

One thing worth taking more seriously than the tablet

Erectile dysfunction is frequently the first sign that the arteries are in trouble, appearing before any cardiac symptom — the penile arteries are narrower, so they show the problem first. Treating the erection without looking at the blood pressure, lipids, blood sugar and weight behind it means treating the symptom and ignoring the warning. That argument is set out in erectile dysfunction as the heart’s early warning system, and what to do about it in exercise and erectile dysfunction.

Tadalafil is one of several first-line options and does not suit every patient. Speak to a urologist before starting any oral erectile dysfunction tablet. When oral therapy is insufficient or contraindicated, review the full range of ED treatment options einschließlich shockwave therapy, intracavernosal injection, and penile prosthesis.

Häufig gestellte Fragen (FAQ)

How does tadalafil work for erectile dysfunction?

Tadalafil is a PDE5 inhibitor that preserves the effect of nitric oxide in the erectile tissue of the penis. When sexual arousal occurs, brain signals travel to the penile tissue, and tadalafil helps it respond more readily, making an erection easier to achieve and maintain. It does not cause spontaneous erections — sexual stimulation is still required, and it has no effect on desire.

How likely is it to work for me?

That depends mainly on why your erections stopped working. Response is good in the general population, substantially lower after radical prostatectomy — where PDE5 inhibitors clearly beat placebo but many men continue to need treatment and only a minority return to how things were before surgery — and lower again in long-standing diabetes. A single overall percentage is more precise than the evidence supports.

How long does tadalafil last compared with sildenafil?

Tadalafil lasts up to 36 hours, compared with roughly 3 to 5 hours for sildenafil, and it is not blocked by a fatty meal. That window is a window of opportunity, not 36 hours of erection, and it does not make a second dose within that period safe. The long duration is also why nitrates must be avoided for 48 hours after a dose, against about 24 hours for sildenafil and vardenafil and about 12 for avanafil.

What are the side effects of tadalafil?

Headache, indigestion, back pain, muscle ache, flushing and a blocked nose, generally mild and temporary. How often they occur depends on the dose: headache affects roughly 15% at the higher as-needed dose, around 11% at the lower as-needed dose, and about 4 to 6% on the low daily dose, with the other effects following the same pattern. Back and muscle ache is more characteristic of tadalafil than of other drugs in the class and is typically self-limited.

What should I do if an erection will not go down?

An erection lasting more than four hours, or one that becomes painful, is priapism and needs an emergency department immediately — not the following morning. Trapped blood loses its oxygen and the erectile tissue can be permanently damaged, so the outcome depends on how quickly it is treated. Say plainly at the desk how long the erection has lasted; it is recognised as an emergency. In Thailand, call 1669.

Who should not take tadalafil?

Anyone taking nitrates for chest pain, or recreational nitrite inhalants sold as poppers, must not take it — the combination can cause a catastrophic fall in blood pressure. The same applies to riociguat for pulmonary hypertension. It is avoided after a recent heart attack or stroke, in unstable angina, in uncontrolled blood pressure, and in severe heart failure. Several drugs including some antifungals, HIV medicines and clarithromycin raise tadalafil levels enough to require a dose reduction.

I take a tablet for my prostate. Can I take tadalafil as well?

Often yes, but it needs discussing rather than assuming, because both lower blood pressure and because the guidance is not consistent. For erectile dysfunction, the labelling advises being stable on the alpha-blocker first and starting the PDE5 inhibitor at the lowest dose. Where the daily low dose is being used to treat the prostate itself, the product labelling does not recommend combining the two and advises stopping the alpha-blocker at least a day beforehand, while the 2026 American Urological Association guideline conditionally recommends that the combination can be used. Tell each prescriber about the other drug, and report feeling faint on standing.

I take tadalafil and I am having chest pain. What should I tell the hospital?

Tell them you have taken tadalafil and when. The standard first treatment for cardiac chest pain is a nitrate, and giving one within 48 hours of a tadalafil dose is dangerous. With that information the team can treat you safely by another route. This is not a detail to leave out through embarrassment — it is the single most useful thing you can say.

Can I buy tadalafil without a prescription?

Although it is sold without prescription in some countries, being assessed first is strongly recommended. Self-medicating risks missing an underlying cause such as cardiovascular disease, diabetes or hormone deficiency — and erectile dysfunction is often the first warning of arterial disease. It also risks a dangerous interaction with medication you may not think of as relevant. Tablets bought online are a further problem: the contents are not guaranteed and counterfeit products are common.

If you are experiencing erectile dysfunction and would like guidance on the most appropriate treatment, Dr. Soarawee Weerasopone offers specialist men’s health consultations at Bangkok Hospital Hauptsitz. Appointments at Samitivej Sriracha Hospital in Chonburi can be arranged by calling the Urology department on 088-022-1445.

Bangkok Hospital Telemedicine is available for patients who cannot attend in person, including international patients — arrange it in advance by email to the Urology department at bhquro@bdms.co.th. Samitivej Sriracha is in-person only. Enquiries about cost are answered by the hospital rather than through this website. A prolonged erection is not a telemedicine problem — go to an emergency department.

Haftungsausschluss: This content is written and reviewed by Dr. Soarawee Weerasopone, a board-certified urologist at Bangkok Hospital Headquarters. It is intended for general education only and does not constitute medical advice, diagnosis or a prescription for any individual. The frequencies in the table above are drawn from product labelling and are given so that you understand how dose affects side effects — dosing and suitability remain individual decisions made with a doctor who knows your full medication list. An erection lasting more than four hours is a medical emergency. No advice, diagnosis or prescription is given through personal messaging channels or social media, and Dr. Soarawee operates no public social media account. In an emergency in Thailand, call 1669.