What is Sildenafil
Sildenafil is a substance used to overcome erectile dysfunction in men. Sildenafil is the active substance in a legendary Viagra. It enhances the blood flow in the male genitals and is effective for erectile dysfunction.
Sildenafil Citrate mechanism of action
Sildenafil Citrate inhibits cGMP-specific phosphodiesterase 5 type (PDE-5). The PDE-5 enzyme does not allow the smooth muscles relax, consequently, when the muscles are tense, the vessels are narrow.
When the action of this enzyme is inhibited, smooth muscles relax, vessels are widened and filled with blood.
PDE-5 is found in all the parts of the body but in some parts its concentration is the highest. It is found in meaningful concentration in the retina, lungs, and penis. Due to this distribution of the enzyme, Sildenafil became so effective for erectile dysfunction.
Sildenafil and other similar substances are known as PDE-5 inhibitors.
Interaction with other drugs. Contraindications.
Before you start taking Sildenafil, consult your doctor and discuss your condition, chronic and current diseases and medications you are currently taking. Not all medications are compatible with Sildenafil.
For example, nitrates including nitroglycerin may cause a sudden drop in the blood pressure. Avoid taking Sildenafil with these substances.
Grapefruit juice and grapefruits may cause undesirable adverse events when you take them with Sildenafil.
Sildenafil side effects can be classified as follows.
- Common side effects – backache, headache, muscle pain, and indigestion.
- Uncommon side effects are runny and stuffy nose and nasal bleeding. Low blood pressure and insomnia may also occur.
- Rare – a sudden loss of vision may occur but mainly in patients in the group of risk. A reduced blood flow to the optical nerve causes this effect. In the group of risk are the following people: diabetic patients, smokers, hypertensive patients, seniors over 50 years old and patients with vision disorders.
- In rare cases, a painful erection may occur that lasts more than 4 hours.
Sildenafil (Viagra) dosage and use
The optimal dose for a healthy man is 50 mg. It is recommended to take the drug an hour before an intercourse.
Sildenafil is the most active within 30 minutes to 4 hours after you take the drug. Do not take Sildenafil more than once a day.
When necessary, the dose may be reduced to 25 mg or decreased to 100mg – this is the maximum daily dose.
You may take Sildenafil with or without food.
When you take Sildenafil, erection occurs only in the presence of a sexual stimulation. The drug itself does not induce erection.
Sildenafil based medications. Generics.
Generics are medications based on the active substance that has already been developed.
New medications are, in essence, new active substances that undergo numerous tests and studies. A drug developer invests a lot of money and in case, the result is positive, it gets the exclusive right (the patent) to sell the new medication. These medications are known as original drugs. While the patent is valid, other companies are not allowed to manufacture analogs with the same active substance.
When the patent expires, other pharmaceutical companies are entitled to manufacture generics.
Pfizer – Sildenafil developer – extends its patent and the patent expires in 2020. However, there is another company Teva that is also allowed to manufacture Sildenafil based generic. The drug is Viagra and it is available in the same doses – 25, 50, and 100 mg.
There are also many illegal Viagra generics. They are sold mainly in developing countries, for example in India. These generics are available in the local markets but they may also enter the markets of developed countries.
Viagra is a prescription drug and a patient needs a prescription or its scanned copy to buy it. Illegal generics are sold over-the-counter without a prescription.