Based upon measurements of sildenafil in semen of healthy volunteers 90 minutes after dosing, less than 0. For treatment of pulmonary arterial hypertension: For oral dosage forms suspension or tablets : Adults—20 milligrams mg 3 times a day. You need a prescription from a doctor to obtain sildenafil. Angina severe chest pain , unstable or Arrhythmia irregular heartbeat, within the last 6 months or Blood vessel problems eg, aortic stenosis, idiopathic subaortic stenosis or Heart attack within the last 6 months or Heart failure or Hypertension high blood pressure or Hypotension low blood pressure or Retinal disorders eye problem or Retinitis pigmentosa an inherited eye disorder or Stroke within the last 6 months —Should not be used in patients with these conditions. This medicine is available on prescription and you can also buy it from most pharmacies. Proper Use Use sildenafil exactly as directed by your doctor.AdWith RexMD you’re saving time and money with our Viagra delivery. Get started now. Reliable E.D. meds prescribed by real doctors. Get your free & private online visit has been visited by 10K+ users in the past monthFree Shipping · Discreet Packaging · Personalized Plan · Real DoctorsTypes: Erectile Dysfunction · Breakouts · Testosterone.  · You’ll typically take Viagra about 1 hour before sex. You can take the drug 30 minutes to 4 hours before you anticipate sexual activity. Based on how well you respond to this dosage and any side. Examples of Viagra’s more commonly reported side effects include: headache. flushing (temporary warmth, redness, or deepening of skin color) stuffy nose. indigestion (upset stomach) mild vision.