It is also used for treating pulmonary arterial hypertension (PAH). It is a selective inhibitor of cyclic guanosine monophosphate specific phosphodiesterase type 5 (PDE5) When the sexual stimulation causes local release of NO, inhibition of PDE5 by sildenafil causes incresaed loevel of cGMP in the corpus cavernosum resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum. : Dosage : The recommended dose is 50 mg per day as needed, appx 1 hour before sexual activity. Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg.Contra- Indications: In patients, on nitrate therapy and with a known hypersensitivity to any component of the tablet Side Effects The drug has certain side effects, that can affect individuals in different ways. The following are some of the side effects, that are often associated with the drug: * Headache * Flushing * Dyspepsia * Nasal congestion * Abnormal vision Disclaimer: The above information is for general understanding of the visitor. Please consult a registered medical practitioner before taking the aforesaid medicine.