Why does erectile dysfunction occur?

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The cases of ED have two common origin fields; all the particular cases have either physical or psychological character. Physical causes include:

  • narrowing of the blood veins delivering blood to the penis, commonly linked to high blood pressure, high cholesterol level or diabetes problems
  • problems with hormonal system
  • surgery or damage of the penis

Psychological reasons of ED are as follows:

  • trait anxiety
  • depressed spirits
  • problems in sexual relationship

Viagra pharmacokinetics and metabolism

Sildenafil starts its action short after consumption, it is quickly absorbed from the stomach. The food can affect the rate of absorption, so it is recommended to take the drug on an empty stomach. The bioavailability of Sildenafil reaches 63%.
The pharmacokinetic parameters of Sildenafil are observed to be dose-proportional. The max daily dose is 100 mg.
The medicine undergoes hepatic metabolism. So its use with certain other medicines (cytochrome P450 3A4 inhibitors such as erythromycin, ketoconazole, itraconazole) and others can modify the plasma levels of sildenafil.
Sildenafil has terminal half-life of about 4 hours. The action starts within 30-120 min post dose when the max plasma concentrations are reached.
The medicine does not affect any semen characteristics.
Sildenafil is eliminated as metabolites in the feces and in the urine.
The pharmacokinetic parameters may be different in special groups of patients including patients older than 65 years of age, patients with kidney or liver disease.

How does Viagra work in the body?

pde inhibitionThe medicine Viagra is specially developed to enhance blood flow to certain part of the body, concerning the treatment of ED – it improves the blood flow to the penile tissues. Thus Viagra produces natural erection. But the process of erection is not simplex, it is a complex of coordinated work of the brain, blood vessels, nerves, muscles.
When Viagra enters the blood stream it enhances the effect of the nitric oxide involved in the process of magnification of the levels of cyclic guanosine monophosphate (cGMP) which produces smooth muscle relaxation in the penis and allows inflow of blood. But the main action of Sildenafil in Viagra is to inhibit an enzyme phosphodiesterase type 5 (PDE5), which makes for diminution of the cGMP.
Sildenafil works only in the presence of sexual stimulation. A person who consumes this medicine should get sexual arousal to have erection.

Before taking Viagra

Before taking Sildenafil medication it is absolutely necessary to consult your doctor, especially if you have other serious conditions.  Viagra should not be taken with any medications used to lower high blood pressure, such as nitrates. Besides, certain medications may interact with Viagra, tell your doctor all the medications you use.
If you suffer from the following conditions inform your doctor, you may need dose adjustment or special tests:
•    heart disease or heart rhythm problems;
•    diabetes;
•    a recent history of a heart attack, stroke, or congestive heart failure;
•    uncontrolled blood pressure;
•    coronary artery disease;
•    liver or kidney disease;
•    sickle cell anemia, multiple myeloma, leukemia, hemophilia;
•    retinitis pigmentosa;
•    cardiovascular disease;
•    priapism condition.
Viagra is a prescription medication with certain side effects. It is indicated to treat ED in men only. Women and children should not use this medication. If you buy Viagra online, read its leaflet carefully before using it.