Imigran price it is taken by mouth with a glass of water approximately 0,5-1 hour before sexual activity. Fildena should not be taken more than once a day. The recommended dose of Cialis is 20 mg it should be taken at least 16 minutes before the sexual activity. The effect persists for 36 hours. Take Cialis once daily and do not exceed the recommended dose. Viagra is contraindicated in patients taking another medicine to treat impotence or using a nitrate drug for chest pain or heart problems. This medicine should not be taken by women and children as well as in patients with a known hypersensitivity to any component of the tablet.