Tadalafil
A long-acting PDE5 inhibitor used for erectile dysfunction, urinary symptoms of BPH and pulmonary arterial hypertension.
Drug card
- Class
- PDE5 inhibitor
- How it works
- Blocking PDE5 so cGMP builds up and smooth muscle relaxes
- Used for
- Erectile dysfunction
- Urinary symptoms of an enlarged prostate (BPH)
- Pulmonary arterial hypertension
- Known for
- Headache
- Back pain, 12 to 24 hours after a dose
- Muscle aches and limb pain
- Its name
- -afil means a PDE5 inhibitor
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does tadalafil work?
A highly selective PDE5 inhibitor, about 700 times weaker against retinal PDE6, with a half-life of about 17.5 hours, so a dose can work for up to 36 hours and it can be taken daily. It also inhibits PDE11 in muscle, prostate and testis, though what that does is unknown.
Like other PDE5 inhibitors: They inhibit phosphodiesterase type 5, the enzyme that breaks down cGMP in smooth muscle. During sexual stimulation nitric oxide raises cGMP in the corpus cavernosum; with PDE5 blocked, cGMP lasts longer, the muscle relaxes and blood flows in, but nothing happens without stimulation. The same effect widens the pulmonary arteries and reaches the smooth muscle of the prostate and bladder.
Uses
What is tadalafil used for?
- Erectile dysfunction
- Urinary symptoms of an enlarged prostate (BPH)
- Pulmonary arterial hypertension
Side effects
Side effects of tadalafil
- HeadacheKnown for
- Back pain, 12 to 24 hours after a doseKnown for
- Muscle aches and limb painKnown for
- Indigestion
- Palpitations or a fast heartbeat
- Low blood pressure, dangerous with nitratesSerious
- PriapismSerious
- Sudden loss of vision (NAION)Serious
- Sudden loss of hearingSerious
- SeizuresSerious
- Heart attack or stroke, reported mainly with heart diseaseSerious
- Severe skin reactions (Stevens-Johnson syndrome)Serious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Contraindicated with nitrates; if one is needed in an emergency, at least 48 hours must pass after the last dose.
- Not with riociguat; take care with alpha blockers, other antihypertensives and heavy drinking.
- Strong CYP3A4 inhibitors such as ritonavir raise its levels, and rifampicin lowers them.
- Avoid in severe kidney or liver impairment.
Good to know: Its long half-life gives a window of up to 36 hours and allows once-daily use for BPH; it is the only PDE5 inhibitor here licensed for BPH.
Remember it
A way to remember it
FLUSH
- F
- Flushing of the face
- L
- Loss of vision or hearing, sudden and rare
- U
- Upset stomach (indigestion)
- S
- Stuffy nose
- H
- Headache
Written for biofideX
Its name
-afil means PDE5 inhibitor
Sildenafil, tadalafil and vardenafil block phosphodiesterase 5, which breaks down cGMP, so smooth muscle relaxes; erectile dysfunction is the best-known use.
- Every drug name stem
Its class
PDE5 inhibitors
Other PDE5 inhibitors with a card:
Easily mixed up with nitrates and methylxanthines.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Tadalafil tablets: label (DailyMed)
- Tadalafil tablets for pulmonary arterial hypertension: label (DailyMed)
- Tadalafil (NCI Thesaurus)
- Tadalafil (NHS)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Reproductive and urinary health
Tadalafil is one of 9 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
Start Practicing