Malegra 25 mg should be taken orally, typically with a glass of water, about 30 minutes to 1 hour before sexual activity. The effects of Sildenafil usually last for about 4 to 6 hours. Common side effects of Malegra 25 mg may include headache, flushing, indigestion, nasal congestion, dizziness, and visual disturbances. Serious side effects are rare but can include priapism (an erection lasting more than 4 hours), sudden vision loss, and sudden hearing loss. If you experience any serious side effects, seek medical attention promptly.