A penile erection happens when the penis fills with blood. This occurs when the blood vessels that supply the penis with blood expand (dilate), and the vessels that take blood away from the penis contract, resulting in an accumulation of blood in the penis.
When a male is sexually aroused, nitric oxide is released into his penis. Nitric oxide triggers a chain of reactions - it makes an enzyme, guanylate cyclase produce cyclic guanosine monophosphate (cGMP). cGMP regulates the contraction and dilation (expansion) of blood vessels that carry blood to and from the penis. The chemical reaction makes the vessels that supply the penis dilate, while those removing blood from the penis contract, resulting in an erection.
Phosphodiesterase-5 (PDE5), another enzyme breaks down (destroys) cGMP. When cGMP is destroyed the blood vessels return to their normal size, effectively ending the erection. Vardenafil inhibits PDE5 degradation of cGMP, i.e. it prolongs cGMP's function. In other words, it helps prolong an erection.
DosageLevitra is available in 2.5, 5, 10, and 20 mg round orange tablets. Most patients start on 10 mg, which is approximately equivalent to 50 mg of sildenafil (Viagra). Patients should take Levitra about 1 or two hours before sex, and should not have more than one tablet every 24 hours. In the UK and some other parts of the world, the only available doses are 5, 10 and 20 mg.
Important informationLevitra can cause a serious and dangerous drop in blood pressure (hypotension) if it is taken with some other prescription medications. The individual may experience dizziness and fainting. There is also a risk of stroke and heart attack.
Those taking medications called nitrates, or recreational drugs called poppers (amyl nitrate and butyl nitrate) should not take Levitra.
The most common side effects among people taking Levitra include stuffy nose, runny nose, headache, stomach upset, dizziness, and flushing. In most cases, these side effects disappear within a few hours. Very rare side effects may include priapism (erection lasts more than four hours, which can damage the penis, patients with priapism should seek medical attention), seeing a blue tinge to objects, and problems differentiating the color green from blue.
Some patients taking Levitra may experience a sudden deterioration in vision in either one or both eyes, this is extremely rare. If this does occur, most likely the patient has a heart condition, an existing eye problem, high cholesterol, diabetes, or hypertension. Patients who experience sudden loss of vision should stop taking the medication and call their doctor immediately.
Patients should tell their doctor about all their medical conditions before taking Levitra, especially if they:
- Have a deformity in the shape of the penis, such as Peyronie's disease
- Have a family history of long QT syndrome (a rare heart condition)
- Have a heart condition, such as arrhythmia, heart failure, or angina
- Have experienced priapism
- Have had a seizure
- Have hearing problems
- Have hemophilia or some kind of bleeding problem
- Have hypotension (low blood pressure) or hypertension (high blood pressure
- Have liver or kidney problems
- Have multiple myeloma, leukemia, sickle cell anemia, or some other kind of blood cell problem
- Have NAION (non-arteritic anterior ischemic optic neuropathy)
- Have recently had a stroke or heart attack
- Have retinitis pigmentosa
- Have stomach ulcers