Tadalafil is a phosphodiesterase type-5 inhibitor.

Onset
30 min

Duration
Up to 36 hours.

Absorption
Well absorbed. Peak plasma concentrations reached within 2 hours. Rate and extent of absorption not affected by food.

Distribution
Widely distributed into tissues. 94% bound to plasma proteins.

Metabolism
Metabolised in the liver mainly by the cytochrome P450 isoenzyme CYP3A4 to inactive metabolites. Mean half-life is 17.5 hours.

Excretion
Excreted mainly as metabolites, in the faeces (61% of the dose), and to a lesser extent the urine (36% of the dose).

Headache, dyspepsia, dizziness, flushing, swelling of eyelids, eye pain, conjunctival hyperemia, back pain, myalgia, visual disturbances, nasal congestion, sudden decrease or loss of hearing, tinnitus.

Potentially Fatal: Stevens–Johnson syndrome, exfoliative dermatitis, severe cardiovascular events e.g. MI, stroke, sudden cardiac death.

Hepatic or renal impairment; CV diseases; anatomical penile deformation; predisposition to priapism; child <18 yr. Discontinue and seek medical advice if there is sudden vision loss or decreased vision in one or both eyes or tinnitus, dizziness or sudden loss or decrease in hearing, while taking Tadalafil. Seek immediate medical advice if erection last > 4 hours.

Concurrent use increased risk of hypotension with α-blockers; increased risk of priapism with other drugs for erectile dysfunction, e.g. alprostadil; increased heart rate with theophylline; decreased tadalafil serum concentration with CYP 3A4 inducers e.g. rifampicin, efavirenz, carbamazepine, nevirapine, barbiturates, phenobarbital, phenytoin, ribabutin; increased tadalafil serum concentration with CYP3A4 inhibitors e.g. azole antifungals, protease inhibitors, cimetidine, macrolides.

Potentially Fatal: Enhanced hypotensive effect with nitrates and nicorandil.

Food Interaction

Concurrent use with grapefruit juice may increase tadalafil levels, while St John's wort may decrease tadalafil levels.

Oral
Erectile dysfunction
Adult: Initially, 10 mg at least 30 min before sexual activity once daily, up to 20 mg as single dose. Max: Not more than once daily. If used with potent inhibitors of CYP3A4, e.g. azole antifungals or protease inhibitors: max 10 mg once every 72 hr.
CrCl (ml/min)       Dosage Recommendation
31-50                  Initial dose at 5 mg/day. Max: 10 mg/48hr
<30                     Max: 5 mg/24hr.
Hepatic impairment: Mild-moderate hepatic impairment (Child-Pugh category A or B): Max dose 10 mg. Severe hepatic impairment (Child-Pugh category C): Not recommended.

May be taken with or without food.

Category B: Either animal-reproduction studies have not demonstrated a foetal risk but there are no controlled studies in pregnant women or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the 1st trimester (and there is no evidence of a risk in later trimesters).

Undetermined

Safety and efficacy not established

No dosage adjustments are needed based on age alone; a greater sensitivity to medications in some older individuals should be considered.

Concurrent use of organic nitrates, nitrates and nitric oxide donors. Men with cardiac disease for whom sexual activity is inadvisable. Recent MI (within 90 days) or stroke (within last 6 mth), hypotension (<90/50 mm Hg), unstable angina, heart failure, uncontrolled arrhythmias or hypertension.

Oral
Store at 15-30°C