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What tadalafil is approved to do
Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor. It relaxes the walls of blood vessels, which is the mechanism behind all its approved uses. The FDA and the NHS list three:
- Erectile dysfunction (ED)
- Symptoms of benign prostatic hyperplasia (BPH), or enlarged prostate
- Pulmonary arterial hypertension (PAH), a condition affecting the blood vessels in the lungs
Approved indications depend on the exact product. In Australia, Cialis is indicated for ED and BPH-related urinary symptoms in adult men. Tadalafil products used for pulmonary arterial hypertension have separate indications and regimens; an ED tablet should not be substituted for a PAH treatment.
Why people call it “the weekend pill”
The big practical difference between tadalafil and sildenafil (Viagra) is duration. Sildenafil lasts roughly four to five hours, while tadalafil can stay active for up to 36 hours. That longer window is where the “weekend pill” nickname comes from.
It also explains why many people find tadalafil less clock-driven. Rather than planning around a short window, they have a much longer period in which the medication is working. It does not mean a continuous effect for 36 hours. Sexual stimulation is still needed.
Daily or as needed? How the two formats differ
Tadalafil is prescribed in two main ways: a low daily dose taken continuously, or a higher dose taken on demand ahead of anticipated sexual activity. Your doctor sets the strength. This isn’t something to work out yourself.
The research points to a few practical decision points:
- Frequent sexual activity. Daily dosing is often considered for men having sex about twice a week or more.
- Urinary symptoms alongside ED. Daily use is also commonly chosen when BPH symptoms are part of the picture, since a single daily tablet can address both.
- Infrequent encounters. As-needed dosing tends to suit people who are sexually active less often.
Consider two hypothetical people. One is in his late fifties with a regular partner and a slow urinary stream. The other has sex occasionally and has no urinary symptoms. The first is a more natural candidate for a daily approach, and the second for as-needed use. Their doctor would still decide based on their full health history.
Side effects: what’s common and why
The most frequently reported side effects are:
- Headache
- Indigestion or heartburn
- Nasal congestion
- Facial flushing
- Back pain
- Muscle aches
Back pain and muscle aches are recognised side effects. Their exact mechanism is not established, so PDE11 inhibition should not be presented as a proven explanation. Report severe, persistent or unusual pain to your doctor.
When a side effect is an emergency
Two rare effects need urgent medical attention:
- Priapism, an erection lasting longer than four hours
- Sudden loss of vision or hearing
If either happens, don’t wait to see whether it passes. Seek emergency care.
The safety rule that matters most: nitrates
Tadalafil must never be combined with nitrates, such as nitroglycerin used for chest pain, or with guanylate cyclase stimulators. Both classes also act on blood vessels, and together they can cause a sudden, life-threatening drop in blood pressure.
This is why a full medication list matters at every appointment. Someone who keeps a nitrate spray in a drawer for occasional chest pain should say so before any PDE5 inhibitor is prescribed. The same applies to anyone buying from a pharmacy: tell the pharmacist about everything you take.
Other blood-pressure medicines and alpha-blockers can add to blood-pressure lowering. Ask your doctor or pharmacist to check the exact combination.
Alcohol and food
Food doesn’t impair tadalafil absorption nearly as much as it does sildenafil’s, so meal timing is less of a concern.
Alcohol is the bigger issue. Heavy drinking markedly raises the risk of orthostatic hypotension, a drop in blood pressure on standing that can cause dizziness, a rapid pulse or fainting. A drink with dinner is a different proposition from a big night out, but the sensible approach is to ask your prescriber what’s reasonable for you.
Uses beyond the approved list
Some clinicians use low-dose daily tadalafil after prostate removal surgery (prostatectomy) as part of penile rehabilitation, with the aim of supporting nerve and arterial blood vessel recovery. This sits outside the three approved uses above, so treat it as a specialist decision made with a urologist, not something to try on your own.
Tadalafil is a pharmaceutical, so there’s no traditional-use history to weigh up.
FAQ
How long does tadalafil last?
It can remain active for up to 36 hours, much longer than sildenafil’s four to five hours.
Can tadalafil treat conditions other than ED?
Yes. It’s also approved for BPH symptoms and pulmonary arterial hypertension.
Is back pain a sign something is wrong?
It’s a recognised side effect, possibly linked to PDE11 activity in muscle, and often appears 12 to 24 hours after a higher dose. If it’s severe or doesn’t settle, speak to your doctor.
Who shouldn’t take it?
Anyone using nitrates or guanylate cyclase stimulators must not take tadalafil.
Is generic tadalafil the same as Cialis?
Cialis is a brand name for tadalafil. The research here doesn’t compare generics in detail, so a pharmacist is the best person to answer product-specific questions.
The takeaway
Tadalafil is a well-established medication with three approved uses and a long duration of action. Most side effects are mild and predictable, a few are emergencies, and one interaction is absolute: nitrates. Tell your doctor or pharmacist about every medicine you take, and make decisions about daily versus as-needed use with them rather than alone.
This article is general information, not medical advice.
Urgent symptoms: stop taking the medicine and seek urgent care for an erection lasting more than four hours, sudden sight or hearing loss, or a serious allergic reaction. For chest pain, stop sexual activity and call 000 in Australia; do not take GTN or other nitrates yourself. Tell emergency staff which ED medicine you took and when. Do not drive yourself if seriously unwell.
Do not combine ED tablets or add extra doses yourself. Tell your prescriber about nitrates, poppers, riociguat, alpha-blockers, blood-pressure medicines, antibiotics, antifungals and HIV medicines. Suitability and interactions depend on the exact product and your health.
Sources and further reading
More information: Good Med Australia health guides.