Phosphodiesterase-5 (PDE-5) inhibitor; erectile dysfunction agent. 

Oral tablet; swallowed with water. 

•  Use as prescribed by doctor (commonly take 1 tablet 30 minutes to several hours before sexual activity).
•  May be taken with or without food. 
•  Not to be taken more than once per day. 
•  Dose may be adjusted by physician depending on response and tolerability.

•  Headache
• Flushing (warmth, redness)
•  Indigestion / dyspepsia
•  Nasal congestion / runny nose
•  Back pain, muscle aches
•  Dizziness
•  In some, changes in vision (blurred vision)
•  Rare but serious: priapism (erection lasting >4 hours), sudden vision loss, hearing loss. 

• Avoid use if also taking nitrates (e.g. nitroglycerin)  risk of dangerous drop in blood pressure. 
•  Inform doctor of cardiovascular disease, hypertension, hypotension, stroke, arrhythmia
•  Use caution with alpha blockers or antihypertensive medications
•  Do not use in women, children
•  If erection lasts >4 hours, seek urgent medical attention
•  Do not use if allergic to tadalafil
•  May interact with other drugs (e.g. antifungals, some antibiotics)
•  Avoid excessive alcohol; grapefruit may interact with tadalafil
•  Discontinue if sudden vision or hearing loss occurs

Other PDE-5 inhibitors: sildenafil, vardenafil, avanafil

It is registered in drug formularies: “JOVAN T 20 FILM-COATED TABLET 20MG” listed in Singapore’s National Drug Formulary (NDF).