Vardenafil is an oral drug that is used to treat impotence, the inability to attain or maintain a penile erection. It has a mechanism of action that is similar to sildenafil (Viagra), and tadalafil (Cialis). Penile erection is caused by the engorgement of the penis with blood. This engorgement occurs when the blood vessels delivering blood to the penis increase in size and increase the delivery of blood to the penis. At the same time, the blood vessels carrying blood away levitra 20mg from the penis decrease in size and decrease the removal of blood from the penis. Sexual stimulation that leads to the engorgement and erection causes the production and release of nitric oxide in the penis. Nitric oxide then activates the enzyme, guanylate cyclase to produce cyclic guanosine monophosphate (cGMP). The cGMP is primarily responsible for increasing and decreasing the size of the blood vessels carrying blood to and from the penis, respectively. Vardenafil prevents an enzyme called phosphodiesterase-5 (PDE-5) from destroying cGMP so that cGMP persists longer. The longer cGMP persists, the more prolonged the engorgement of the penis. Vardenafil was approved by the FDA in August 2003.
The most common side effects of vardenafil are facial flushing (reddening), headaches, stomach upset, diarrhea, flu like symptoms, and nausea. Vardenafil also may cause chest pain, low blood pressure, blurred vision and changes in color vision, abnormal ejaculation and priapism (painful erection lasting more than 6 hours). Patients should seek immediate medical help if they experience an erection lasting more than 4 hours. Rare cases of sudden loss of hearing have been reported with phosphodiesterase inhibitors such as vardenafil, sometimes associated with ringing in the ears and dizziness. If changes in hearing occur, patients should discontinue their vardenafil and seek immediate medical attention.
For most individuals, the recommended dose of vardenafil regular tablets is 10 mg per day taken 60 minutes before intercourse. If there is no response or side effects, the dose may be increased to 20 mg or, if there are side effects, it may be reduced to 5 mg. Individuals 65 years of age or older should begin therapy with 5 mg. Individuals who are taking medications that increase the blood levels of vardenafil should start treatment with 2.5 to 5 mg of vardenafil. (See drug interactions.)
Orally disintegrating tablets (ODT) are not interchangeable with regular vardenafil tablets because they are better absorbed and produce higher blood levels than regular tablets. The recommended dosing when using ODT is one tablet 60 minutes before intercourse. Only one tablet should be used per day. It should be placed on the tongue until it disintegrates and should not be swallowed with water.
The breakdown and elimination of vardenafil from the body is inhibited by erythromycin, clarithromycin (Biaxin), ketoconazole (Nizoral), itraconazole (Sporanox), indinavir (Crixivan), ritonavir (Norvir), atazanavir (Reyataz), grapefruit juice. Therefore, these drugs increase the concentration of vardenafil in the blood and should not be combined with vardenafil. Vardenafil reduces the concentration of ritonavir and indinavir and may reduce the effect these drugs. Vardenafil increases heart rate and also exaggerates blood pressure lowering effects of nitrates (for example, nitroglycerine). In patients with chest pain (angina), particularly those who take nitrates,, vardenafil can cause chest pain by increasing heart rate and lowering blood pressure. Therefore, patients with angina should not use vardenafil. Vardenafil also exaggerates the blood pressure lowering effects of alpha-blocking drugs, for example, terazosin (Hytrin), and should not be used by individuals who also use alpha-blockers. Vardenafil also adds to the blood pressure reducing effect of other medications.