The characteristics of how the medicine is absorbed metabolized and its time of elimination from the body determine the time of action and the max effect reached at the particular point. Besides, these characteristics help to understand the right dose for particular groups of patients.
Viagra (sildenafil) is fast soaked up in the stomach and enters the blood stream. The bioavailability of the medicine is high. The elimination of the drug happens in the liver. The half-life of the drug is up to 4 hours.
Maximum plasma concentrations distinguished is 30-120 minutes post oral dose.
After oral administration, sildenafil is excreted as metabolites in the feces (80% of oral dose) and in the urine (13% of oral dose).
There are several factors which can influence on the treatment of ED in men. One of such factors is the age of a patient. The age is related to the increased plasma levels of sildenafil and decreased clearance of the drug from the body.
Patients older than 60 years of age should receive lower doses of Viagra. They should start with the 25 mg pill of Viagra. Then with respect to the tolerance to the drug, they can use 50 mg pill of Viagra.
Older patients have greater chance for side effects of Viagra due to increased sildenafil concentrations in the blood and the use of other drugs which may amplify the effect of sildenafil.
Patients in their 60 years of age and older often use nitrates for their heart problem. The use of Viagra concomitantly with nitrates is not allowed because of high risk of severe drop in blood pressure.
More senior men should consult a doctor about Viagra use, dose, frequency of dosing and side effects before adopting this drug. Consultation of specialists (urologist, endocrinologist) may also be needed.
Viagra has raised a great interest since it became available in 1998. The concern of patients occurred due to the reports of serious side effects associated with Viagra use. The serious side events appear usually in relation to high doses of Sildenafil consumed by men. Besides, men with certain health conditions have greater risk for serious side effects.
Still serious side effects are very rare and happen only a small number of men.
Medical help is required if a man experiences severe allergic reactions, swelling of the face, neck, tongue, hives, vision problems, hearing loss, heart rhythm problem, general ill-feeling and others.
More usual Viagra side effects are:
• warmth or redness of face, neck, or chest;
• upset stomach;
These side effects occur in a small number of men and in general vanish when the body gets used to the effects of the medicine.
Taking the medicine in the right way practically eliminates the risk of side effects development and guarantees the achievement of therapeutical results.
Viagra is usually used before sexual activity, about 30 minutes up to 4 hours. The dose of the medicine should be followed, dose increases are discussed with a doctor first.
Viagra is active for about 4 hours after the oral intake. The medicine can be used once in 24 hours. More often use may result in increased drug concentrations in plasma which induces chance of side events.
Doctors recommend patients using Viagra on an empty stomach or with light food. The pill is washed down with water. Drinking alcohol with Viagra is not commended.
The dose of Viagra is determined by the doctor. The choice of the dose is very important as the lower dose may be not effective for some men, higher dose may cause side effects. The dose of 50 mg of the drug is recommended for most men who are generally healthy. Lower doses are usually determined for persons who have kidney or liver problems. Higher dose of 100 mg is prescribed for those men who have serious ED problem (or a long history of impotence).
In general a man can find out his best dose of the drug by trying different doses within the recommended range (the max is 100 mg).
The frequency of Viagra use is also very important. The drug must not be used more often than once in 24 hours. It is used on the as needed basis.
Careful use of Viagra is recommended when a person is taking other meds.