How does tadalafil work is primarily used to treat erectile dysfunction (ED), a condition where men cannot achieve or maintain an erection sufficient for sexual activity. Tadalafil typically starts working within 30 to 60 minutes after ingestion, and it can be taken with or without food. Its effects can last for up to 36 hours, depending on the individual. Tadalafil works by inhibiting the enzyme PDE5, which is responsible for breaking down cGMP, a molecule that helps relax the smooth muscle in the penis and allows for increased blood flow, leading to an erection.