It affects the way the medicine works. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it. Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance and inducers of these isoenzymes may increase sildenafil clearance. 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. Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.Side Effects. Dizziness, headache, flushing, or stomach upset may occur. Vision changes such as increased sensitivity to light, blurred vision, or trouble telling blue and green colors apart may. VIAGRA is supplied as blue, film-coated, rounded-diamond-shaped tablets containing sildenafil citrate equivalent to 25 mg, 50 mg, or mg of sildenafil. Tablets are debossed with PFIZER on one side and VGR25, VGR50 or VGR on the other to indicate the dosage strengths. Close. If you have these symptoms, stop taking VIAGRA and contact a doctor right away. have or have had heart problems such as a heart attack, irregular heartbeat, angina, chest pain, narrowing of the aortic valve, or heart failure. have low blood pressure, or high blood pressure that is not controlled.