Tadalafil

Key facts

• Tadalafil (the ingredient in Cialis and generics) is a PDE5 inhibitor. It relaxes blood vessels so more blood reaches the penis during arousal, and it only works with sexual stimulation.
• A single dose can work for up to 36 hours, and a lower daily dose is also available for continuous use. Food has little effect on how well it works.
• Never take tadalafil with nitrate heart medicines (glyceryl trinitrate, isosorbide) or the pulmonary-hypertension drug riociguat. Together they can drop your blood pressure to dangerous levels.
• Seek urgent care for an erection lasting more than 4 hours, or sudden loss of vision or hearing.

What tadalafil treats

Tadalafil treats erectile dysfunction, the inability to get or keep an erection firm enough for sex. A low daily dose also treats benign prostatic hyperplasia, non-cancerous enlargement of the prostate that causes a weak stream and frequent urination, by relaxing smooth muscle in the prostate and bladder neck. Some men take one daily dose covering both conditions. It is not a treatment for angina, and it does not increase desire.

How tadalafil works

An erection depends on a signal molecule called cyclic GMP relaxing the blood vessels in the penis so they fill with blood. An enzyme, PDE5, breaks that molecule down. Tadalafil blocks PDE5, so cyclic GMP lasts longer and the vessels stay relaxed once arousal begins. The same effect on smooth muscle eases prostate urinary symptoms.

Before you take it

• Do not use tadalafil if you take any nitrate medicine or riociguat, or if a doctor has told you sex is too risky for your heart.
• Tell your prescriber about alpha-blockers, other blood-pressure medicines, recent heart attack or stroke, uncontrolled blood pressure, and severe liver or kidney disease. These may change your dose or rule the drug out.
• An erection lasting over 4 hours (priapism) can permanently damage the penis. Men with sickle cell disease, myeloma or leukaemia carry a higher risk.
• Buy only from a licensed pharmacy. Tadalafil is widely counterfeited, and fakes with wrong doses or contaminants are a documented cause of harm.

Side effects

Common effects fade as the dose wears off: headache, facial flushing, indigestion, back or muscle ache, and a blocked or runny nose.

Stop and seek urgent medical care for any of these:

• An erection lasting more than 4 hours.
• Sudden loss or dimming of vision in one or both eyes.
• Sudden hearing loss, sometimes with ringing or dizziness.
• Chest pain, a fast or irregular heartbeat, or fainting.

Safety essentials

• The nitrate rule is absolute: tadalafil stays in the body far longer than other PDE5 inhibitors, so no nitrate should be given for at least 48 hours after your last dose. If you get chest pain during sex, tell emergency staff you have taken it.
• Combining tadalafil with an alpha-blocker can cause a sudden drop in blood pressure on standing; your prescriber will space or adjust the doses.
• Do not take more than one on-demand dose in 24 hours, and do not combine it with other erectile-dysfunction treatments.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.