Cialis is the trade name for the generic name tadalafil, 2.5 mg is one of its sizes, and the drug’s effects usually last for about 36 hours after administration. The drug is a cyclic guanosine monophosphate specific phosphodiesterase 5 selective inhibitor, mainly used for the treatment of premature ejaculation and male erectile dysfunction. Sexual stimulation is required for the drug to work after taking it. Generally, tadalafil tablets, when taken as needed, can improve erectile function for up to 36 hours. However, the exact amount of time it lasts varies depending on the individual’s constitution. To ensure the safety of the medication, patients are advised to take the medication as prescribed by their doctor. In particular, patients with a history of heart disease or who have recently taken nitrate medications should not use the medication inappropriately to prevent cardiac events or hypotensive events.