Tadalafil and sildenafil differ in terms of onset of action and duration of action. 1. Onset of action: Tadalafil has an onset of action of about 2 hours, while sildenafil has a faster onset of action of about 1 hour. 2. Duration of action: Tadalafil is a long-acting phosphodiesterase type 5 inhibitor with a longer maintenance time of 24-36 hours, while sildenafil is a short-acting phosphodiesterase type 5 inhibitor with a maintenance time of 6-8 hours. Adverse reactions such as dizziness, eye pain, headache, facial flushing, congestion, and nasal congestion may occur after taking tadalafil and sildenafil. Both tadalafil and sildenafil belong to the group of phosphodiesterase type 5 inhibitors that treat erectile dysfunction. The combination of these two drugs with nitrates is prohibited, and the drug is contraindicated in women, people who are allergic to the product, children, and people whose recent cardiovascular status makes them unfit for sexual intercourse. Tadalafil and sildenafil have their own advantages and disadvantages, and it is recommended to consult a specialist to choose the appropriate treatment according to the condition and personal needs.