Tadalafil: what it treats, how to take it, side effects
Last updated September 3, 2026.
Tadalafil is a PDE inhibitor - it relaxes blood vessels to increase blood flow where it is needed. You may know it as Cialis for erectile dysfunction and prostate symptoms, or Adcirca for pulmonary arterial hypertension. One molecule, three jobs - and one absolute rule about nitrates.
What does it treat?
As Cialis: erectile dysfunction and the urinary symptoms of an enlarged prostate - hesitation, dribbling, weak stream, incomplete emptying, frequency, urgency. As Adcirca: pulmonary arterial hypertension, improving the ability to exercise. For ED the honest framing: it does not cure ED, does not increase desire, and does not prevent pregnancy or sexually transmitted infections.
How do you take it?
For ED, two legitimate patterns your doctor chooses between: as needed, at least 30 minutes before sexual activity, never more than once in 24 hours - or once daily at the same time, freeing the timing from the activity entirely. For BPH or PAH: once daily, the full daily dose at one time, same time every day. Certain health conditions and medications mean lower doses or less frequent dosing - the prescriber calibrates. Never more than prescribed. Missed dose on a daily schedule: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: headache, indigestion or heartburn, nausea, diarrhea, flushing, pain in the stomach, back, muscles, arms, or legs, and cough.
- Serious - call your doctor immediately or get emergency care: sudden decrease or loss of vision; blurred vision or color-vision changes - blue tinge, trouble telling blue from green; sudden decrease or loss of hearing or ringing in the ears; an erection lasting longer than 4 hours - that one is an emergency, full stop; dizziness; and chest pain.
Who should not take it?
Anyone taking nitrates in any form - nitroglycerin, isosorbide dinitrate or mononitrate, patches, sprays, ointments - or riociguat: the combination drops blood pressure dangerously, and the label says your doctor will probably not prescribe it. Street drugs containing nitrates - poppers - count exactly the same. Alpha-blockers, many antifungals, antibiotics, HIV medications, and blood-pressure drugs change the dosing - the full medication list matters. Never take Cialis and Adcirca together - same molecule, double dose. Chest pain during sex is a stop-and-get-help event, and tell the paramedics you take tadalafil, because the nitrate rule follows you into the ambulance.
When is it an emergency?
An erection past 4 hours, sudden vision or hearing loss, or chest pain is emergency care. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why can't I take tadalafil with nitrates?
Both relax blood vessels - together they can crash blood pressure to dangerous levels. MedlinePlus names the forms: nitroglycerin tablets, sprays, patches, pastes, ointments, isosorbide dinitrate and mononitrate, riociguat, and street poppers count too. The rule is absolute, and it follows you into emergencies: if you have chest pain, the responders need to hear "I take tadalafil" before anyone reaches for nitroglycerin.
Daily or as-needed - how do we choose?
Life pattern. As-needed (at least 30 minutes before activity, max once per 24 hours) suits infrequent, planned intimacy. Daily low-dose removes the scheduling entirely - activity any time between doses - and it is the version that also treats prostate symptoms. The decision is a real conversation with your prescriber about frequency, spontaneity, and whether the urinary symptoms are in the mix.
Why is the 4-hour erection such an emergency?
Priapism: an erection sustained past 4 hours traps blood, starves the tissue of oxygen, and can cause permanent damage within hours. It is rare, but it is the one tadalafil effect where waiting is the mistake - it goes straight to the emergency room, not to a phone call, not to morning. Every prescriber names it up front because the outcome is decided by speed.
Why can't I take Cialis and Adcirca together?
They are the same molecule - tadalafil - in different branding for different conditions. Taking both is a double dose of the same drug, with the blood-pressure and side-effect stakes doubled. MedlinePlus states it plainly: only one of these products at a time. If your prescriptions come from two specialists, each needs to know about the other.
Does tadalafil increase desire?
No - and MedlinePlus says it directly: it does not cure ED and does not increase sexual desire. It is plumbing, not motivation - it improves blood flow during sexual stimulation, so stimulation is still required for it to work at all. Low desire itself is a different conversation, with different causes - hormones, mood, medications, relationship - and different fixes.
What happens if I miss a dose of daily tadalafil?
Take it as soon as you remember, unless it is almost time for the next one - then skip it and never double up. Doubling stacks the headache, flushing, and blood-pressure effects. The as-needed version has no missed dose to manage - just the once-per-24-hours ceiling, which is a hard ceiling.