Pharmacology

Sildenafil protects cyclic guanosine monophosphate (cGMP) from degradation by cGMP-specific phosphodiesterase type 5(PDE5) in the corpus cavernosum. Nitric oxide(NO) in the corpus cavernosum of the penis binds to guanylate cyclase receptors, which results in increased levels of cGMP, leading to smooth muscle relaxation (vasodilation). This smooth muscle relaxation leads to vasodilation and increased inflow of blood into the spongy tissue of the penis, causing an erection.
Sildenafil is a potent and selective inhibitor of cGMP-specific phosphodiesterase type 5(PDE5), which is responsible for degradation of cGMP in the corpus cavernosum.Without sexual stimulation, and therefore lack of activation of the NO/cGMP system, sildenafil should not cause an erection.

Interactions

Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines.

• Care should be exercised by people who are also taking protease inhibitors for the treatment of HIV infection. Protease inhibitors inhibit the metabolism of sildenafil, effectively multiplying the plasma levels of sildenafil, increasing the incidence and severity of side effects.
• Those using protease inhibitors are recommended to limit their use of sildenafil to no more than one 25 mg dose every 48 hours. Other drugs that interfere with the metabolism of sildenafil include erythromycin and cimetidine, both of which can also lead to prolonged plasma half-life levels. The use of sildenafil and an a1 blocker (typically prescribed for hypertension or for urologic conditions, such as benign prostatic hypertrophy) at the same time may lead to low blood pressure, but this effect does not occur if they are taken at least 4 hours apart.

Side Effects

Headache, Flushing, Indigestion, Nasal congestion, Impaired vision, and Blurred vision.

Precautions & Warnings

Talk to your doctor, pharmacist or nurse before taking this medication:

• If you have sickle cell anaemia (an abnormality of red blood cells), leukaemia (cancer of blood cells), multiple myeloma (cancer of bone marrow).
• If you have a deformity of your penis or Peyronie's Disease.
• Nitrate containing pills should be avoided with the consumption of this medication as their combination could lead to severe health complications in the person. This is because, nitrate pills are used in the treatment of chest pain and troubles relating to heart.
• If you currently have a stomach ulcer, or a bleeding problem (such as haemophilia).
• If you experience sudden decrease or loss of vision, stop taking this medication and contact your doctor immediately.
• You should not use this medicine with any other oral or local treatments for erectile dysfunction.
• You should not use this medicine with treatments for pulmonary arterial hypertension (PAH) containing sildenafil or any other PDE5 inhibitors.
• You should not take this if you do not have erectile dysfunction.
• You should not take this if you are a woman, children and teenager
• The medication should not be consumed on a daily basis as it can lead to a habitual action within the person. Thus, this kind of consumption could lead to addiction of this medication in the person. Thus, this can bring out adverse side effects over the person.
• If you have known hypersensitivity to sildenafil

Sildenafil is not indicated for use by women.
There are no adequate and well-controlled studies in pregnant or breastfeeding women.