Penegra 100 mg (sildenafil 100 mg) overdose means taking more than the recommended amount or taking it too frequently. A higher dose can increase the severity and likelihood of side effects. Possible overdose effects include: Severe headache Flushing and feeling very hot Dizziness or lightheadedness Fainting due to low blood pressure Fast or irregular heartbeat Nausea or indigestion Vision changes (such as blurred vision or color changes) A prolonged or painful erection (priapism) lasting more than 4 hours, which needs urgent medical attention The risk is higher if Penegra is combined with: Nitrate medicines for chest pain (a dangerous blood-pressure drop can occur) Certain blood-pressure medicines Large amounts of alcohol Other erectile dysfunction medicines (such as tadalafil or other PDE5 inhibitors) If someone has taken more than prescribed and has chest pain, fainting, severe dizziness, sudden vision/hearing problems, or an erection lasting over 4 hours, they should seek emergency medical help.