Tadalafil review
The long one — up to 36 hours, or a daily dose that ends the clock-watching
Our overall score
Written by J. Porter, MPH
Medically reviewed by A. Vance, MD
Last reviewed
The short version
Tadalafil's defining feature is its 17-hour half-life, which gives an on-demand dose a window of up to 36 hours and makes a low daily dose practical. For many people that removes the planning problem entirely, which is why it has become the most-prescribed option despite costing slightly more than sildenafil.
Best for: People who dislike timing doses around sex, or who also have benign prostatic hyperplasia.
What works
- A single dose covers a day and a half, so sex does not have to be scheduled
- Food has essentially no effect on absorption
- A 2.5–5 mg daily option makes treatment continuous rather than event-based
- Also treats BPH urinary symptoms, which often coexist with ED
What to watch
- Back pain and muscle aches affect a noticeable minority
- Side effects last longer because the drug does
- The long half-life is a drawback if you need to take nitrates — the required washout is longer
Get emergency help for these
- An erection lasting more than 4 hours — this can cause permanent damage
- Sudden loss of vision or hearing
- Chest pain during or after sex — tell responders you took a PDE5 inhibitor
At a glance
- Generic name
- Tadalafil
- Brand name
- Cialis
- Drug class
- PDE5 inhibitor
- FDA approved
- 2003
- Typical doses
- As needed: 5 mg, 10 mg, 20 mg · Daily: 2.5 mg, 5 mg
- Usual starting dose
- 10 mg as needed, or 2.5–5 mg once daily
- Onset
- 30–60 minutes, occasionally up to 2 hours
- Duration
- Up to 36 hours
- Half-life
- ~17.5 hours
- Effect of food
- None of clinical significance — food does not meaningfully delay it
- Generic available
- Yes
- Typical cost
- Roughly $0.60–$5 per tablet for the generic with a discount cardChecked July 15, 2026. Prices vary widely by pharmacy — treat as a ballpark, not a quote.
- Also approved for
- Benign prostatic hyperplasia (BPH) · Pulmonary arterial hypertension (as Adcirca)
Why the half-life changes everything
Tadalafil is the same class of drug as sildenafil — a PDE5 inhibitor that preserves cGMP so blood flows into the penis more readily during arousal. What separates it is pharmacokinetics. Tadalafil's half-life is roughly 17.5 hours, against about 4 hours for sildenafil.
That single number produces every practical difference. An on-demand dose stays clinically useful for up to 36 hours, which is where the nickname “the weekend pill” came from. And because the drug accumulates predictably, a low daily dose maintains a steady level in the bloodstream — so there is no dose to time, and no conversation about whether tonight is a pill night.
On-demand or daily?
Both work. The choice is mostly about how often you have sex and how much the ritual of dosing bothers you.
| As needed (10–20 mg) | Daily (2.5–5 mg) | |
|---|---|---|
| Best when | Sex is occasional or planned | Sex is frequent or spontaneous |
| Timing | Take 30–60 minutes ahead | Same time each day, no planning |
| Coverage | Up to 36 hours per dose | Continuous once at steady state |
| Time to full effect | Same day | About 5 days to reach steady state |
| Monthly cost | Depends on frequency | Fixed — usually higher if you have sex rarely |
| Also treats BPH | Not the approved route | Yes, 5 mg is approved for BPH |
Side effects
The side effect list overlaps heavily with sildenafil's — headache, flushing, indigestion, nasal congestion — with two differences worth knowing.
First, back pain and muscle aches are distinctive to tadalafil. They usually appear 12 to 24 hours after a dose, feel like a dull ache in the lower back or thighs, and resolve within about two days. They are not dangerous, but for some people they are the reason to switch.
Second, visual side effects are less common than with sildenafil, because tadalafil is more selective for PDE5 over the PDE6 enzyme found in the retina.
The flip side of the long half-life: when a side effect does occur, it tends to persist longer than it would with a shorter-acting drug.
Safety and interactions
This matters more with tadalafil than with the others. Because the drug lingers, the interval you must wait before nitrates can be given safely is substantially longer — a real consideration if you have cardiac disease and might need emergency nitroglycerin. Make sure tadalafil is on the medication list your emergency contacts and clinicians can see.
- Riociguat (Adempas) — contraindicated
- Alpha blockers — start at the lowest dose and separate administration times
- Strong CYP3A4 inhibitors (ritonavir, ketoconazole, clarithromycin) — dose limits apply
- Significant kidney or liver impairment — dosing is capped, and daily dosing may not be recommended
Switching from sildenafil
There is no taper or washout required to move between PDE5 inhibitors; you simply do not take both on the same day. Dose equivalence is approximate — 10 mg of tadalafil is roughly in the territory of 50 mg of sildenafil, and 20 mg near 100 mg — but response varies enough between individuals that your prescriber will likely adjust after a few tries.
Common questions
Does tadalafil really last 36 hours?
The 36-hour figure describes the window in which the drug remains capable of assisting an erection with arousal — not a 36-hour erection. Most people find the effect strongest in the first several hours and gradually tapering after that.
Should I take daily or as-needed tadalafil?
Roughly: if you expect sex more than about twice a week, or you value not planning, daily usually works out better. If sex is occasional, on-demand dosing is typically cheaper.
Why does tadalafil give me back pain?
The mechanism isn't fully settled, but it's thought to involve PDE11 inhibition in muscle tissue. It typically starts 12–24 hours after a dose and clears within 48 hours. If it persists or is severe, that's worth reporting to your prescriber.
Can I switch from daily to as-needed dosing?
Yes, and your prescriber can adjust either way. Coming off daily dosing, the drug clears over several days, so you may not need an on-demand dose immediately.
Is tadalafil safe to take long-term?
Daily tadalafil has been studied and prescribed for years, including for BPH, and is generally considered appropriate for long-term use in people without contraindications. Long-term use should still be reviewed periodically with a clinician.
Sources
- 1.Cialis (tadalafil) prescribing information — U.S. Food and Drug Administration
- 2.Erectile Dysfunction: AUA Guideline — American Urological Association
- 3.Management of Benign Prostatic Hyperplasia (BPH) — American Urological Association