Malegra 100 mg contains sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor used for erectile dysfunction. It is taken only once per day mainly because of how long the drug stays active in the body and to avoid dangerous side effects. 1. Drug stays active for several hours Sildenafil typically: Starts working in 30–60 minutes Works for about 4–6 hours (sometimes slightly longer in some men) Taking another dose within the same day can cause the drug to accumulate unnecessarily, increasing risk without improving benefit. 2. Risk of side effects increases with repeated dosing Taking more than one dose in 24 hours can raise the risk of: Severe headache Dizziness or fainting (low blood pressure) Flushing and rapid heartbeat Vision changes (blurred or blue-tinted vision) Priapism (painful erection lasting >4 hours — a medical emergency) 3. Blood pressure safety Sildenafil affects blood vessels. Repeated dosing too soon can cause: Excessive drop in blood pressure Dangerous interactions with alcohol or heart medicines (especially nitrates) 4. Standard medical guideline For safety, doctors recommend: Maximum 1 dose in 24 hours Using only when needed, not continuously throughout the day Bottom line Malegra 100 mg is limited to once daily because its effects last several hours and repeating the dose within 24 hours can significantly increase side effects and health risks without improving performance. If you want, I can compare sildenafil (Malegra) with tadalafil options in terms of duration and dosing flexibility.