The breakdown and elimination of Levitra from the body is inhibited by erythromycin, ketoconazole (Nizoral), itraconazole (Sporanox), indinavir (Crixivan) and ritonavir (Norvir). Therefore, these drugs increase the concentration of Levitra in the blood. If these drugs are being used at the same time as Levitra, the dose of Levitra should be reduced in order to avoid side effects from Levitra.

Levitra reduces the concentration of ritonavir and indinavir and may reduce the effect these drugs.

Levitra increases the heart rate and also exaggerates the blood pressure lowering effects of nitrates (e.g. nitroglycerine). In patients who take nitrates for chest pain (angina), Levitra could cause chest pain by increasing heart rate and lowering blood pressure. Therefore, patients with angina should not use Levitra. Levitra also exaggerates the blood pressure lowering effects of alpha-blocking drugs, e.g. terazosin (Hytrin), and should not be used by individuals who also use alpha-blockers.

Levitra comes as a tablet to take by mouth. It is usually taken as needed, with or without food, 60 minutes before sexual activity. Levitra usually should not be taken more often than once every 24 hours. If you have certain health conditions or are taking certain medications, your doctor may tell you to take Levitra less often. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take Levitra exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.