If you forget to take it If you have pulmonary hypertension and you forget to take a dose of sildenafil, take it as soon as you remember unless it’s nearly time for your next dose. With private prescriptions, the same piece of paper can be re-used for subsequent treatment. Sorry something went wrong with your subscription Please, try again in a couple of minutes Retry. Patients should always ask their doctors for medical advice about adverse events. The most common side effects of VIAGRA: headache; flushing; upset stomach; abnormal vision, such as changes in color vision such as having a blue color tinge and blurred vision; stuffy or runny nose; back pain; muscle pain; nausea; dizziness; rash.AdSave Time & Money with Online Prescription for Viagra, Cialis, Sildenafil and Tadafil. Free & Private Online Consultant with Real Doctors. Reliable E.D. Meds Shipped : Premature Ejaculation · Sexual Health · Privacy Policy. About sildenafil (Viagra) Sildenafil is a medicine used to treat erection problems (erectile dysfunction). Sildenafil is also sometimes used to treat pulmonary hypertension (high blood pressure in the blood vessels that supply the lungs). If you have erection problems sildenafil works by temporarily increasing blood flow to your penis when. AdSay Goodbye to Performance Anxiety and Hello to Improved Sexual Stamina! Reviews and Comparisons Of The Best Male Enhancement Products. See Which Products WorkK+ visitors in the past month.