Cenforce 25 mg contains sildenafil 25 mg, headache can occur after taking the tablet, often while the medicine is active. It is a common side effect caused partly by sildenafil's blood-vessel–relaxing effects. In clinical trials, headache occurred in about 16% of people taking 25 mg sildenafil, compared with 7% taking placebo. The rate increased with higher doses: 21% at 50 mg and 28% at 100 mg. D DailyMed +1 What to expect It may begin within a few hours after taking the tablet. It is usually mild and temporary. Drinking enough water and avoiding excessive alcohol may help. Don't increase the dose just because you experience little effect initially. Seek urgent medical attention if the headache is sudden and extremely severe, or occurs with chest pain, fainting, severe vision problems, or other unusual neurological symptoms. If you tell me how long after taking Cenforce 25 mg your headache starts and how severe it is, I can help you determine whether it sounds like a typical sildenafil side effect.