Duratia 90 mg can be bought at any local medical store and online. However, it is important to follow your doctor's instructions closely. This medication should be taken an hour before sexual contact and should be taken with water. It should not be taken with alcohol, caffeine, aerate drinks, or nitrates. In case of an overdose, contact your doctor immediately. Likewise, you should not take Duratia more often than prescribed by your physician.