Tadalis SX 20 mg typically starts working within 30 minutes to 1 hour after ingestion, although the onset may vary among individuals. Its effects can last up to 36 hours, allowing for greater flexibility in timing sexual activity. Common side effects of Tadalafil may include headache, flushing, indigestion, back pain, muscle aches, nasal congestion, and changes in vision (such as blurred vision or color distortion). Serious side effects such as priapism (prolonged erection lasting more than 4 hours) are rare but require immediate medical attention.