Quick facts
Generic name: tadalafil · Class: PDE5 inhibitor · FDA approved: 2003 · Onset: ~30–45 min · Duration: up to ~36 hours · Status: prescription only
Background
Tadalafil was approved by the FDA in 2003 and quickly distinguished itself from earlier ED pills by its remarkably long duration of action. Because it can remain effective for up to about a day and a half, it earned the nickname "the weekend pill," reducing the need to time a dose closely to sexual activity.
How tadalafil works
Like other PDE5 inhibitors, tadalafil blocks the PDE5 enzyme, preserving cyclic GMP so blood vessels in the penis relax and fill more easily during arousal. What sets it apart is its pharmacology: tadalafil has a much longer half-life than sildenafil or vardenafil, which is why its window of effect is so extended.
Two ways to take it: as-needed vs daily
Tadalafil is unique among the major ED drugs in offering two approaches:
- As needed: a higher dose taken before anticipated activity, with effect lasting up to ~36 hours.
- Low-dose daily: a small dose taken every day so that you are ready at any time, without planning around a single dose. This option suits men who prefer spontaneity or who also have urinary symptoms from an enlarged prostate.
Food does not significantly affect how tadalafil works, unlike sildenafil and vardenafil.
A dual benefit: ED and BPH
Tadalafil is also FDA approved to treat the bothersome urinary symptoms of benign prostatic hyperplasia (BPH) — the enlarged prostate that causes weak stream, urgency and nighttime urination. For men who have both ED and BPH, a single daily medication can address both, which is a meaningful clinical advantage. Learn about prostate care →
What clinical research shows
Tadalafil has been studied in numerous randomized, placebo-controlled trials across diverse groups of men, including those with diabetes and following prostate surgery. The evidence consistently shows significant improvement in erectile function versus placebo. Separate trials supporting its BPH indication demonstrated meaningful improvement in urinary symptom scores, leading to its dual approval.
Common side effects
- Headache
- Indigestion
- Back pain and muscle aches (a side effect more characteristic of tadalafil, usually appearing 12–24 hours after dosing and resolving on its own)
- Facial flushing
- Nasal congestion
Important safety information
- Never combine with nitrates. Because tadalafil lasts so long, the nitrate interaction window is also longer — making this caution especially important.
- Use care with alpha-blockers and other blood-pressure medications.
- Discuss heart health before starting.
- Get it only by prescription from a licensed pharmacy; avoid counterfeit products sold online.
Frequently asked questions
Why is Cialis called "the weekend pill"?
Tadalafil can stay effective for up to about 36 hours, allowing more spontaneity over a weekend. Sexual stimulation is still required.
Should I choose daily or as-needed dosing?
That depends on how often you're sexually active, whether you have BPH symptoms, and your preferences. Your physician will help you decide.
Can tadalafil really treat my prostate symptoms too?
Yes — it is FDA approved for BPH symptoms and can treat ED and BPH together under medical supervision.
Is generic tadalafil available?
Yes. Generic tadalafil contains the same active ingredient and meets FDA standards. Your physician or pharmacist can advise on dosing and cost.
Related reading: Generic Cialis (tadalafil): is it safe & how to check quality · Viagra vs Cialis vs Levitra · Compare all ED medications