Before starting, stopping, or changing any medications while taking sildenafil, please get the advice of your doctor or pharmacist. At the same time, on-treatment function was better in treated patients who were less impaired at baseline. 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. The primary endpoint was time to limiting angina in the evaluable cohort. Similar values for pharmacokinetic parameters were seen in normal volunteers and in the patient population, using a population pharmacokinetic approach. A risk management plan has been developed to ensure that Viagra is used as safely as possible.Cialis is only available by prescription in the United States. Viagra: Additionally, a study from Trusted Source. found that combining L-arginine and sildenafil (Viagra) worked better for. Most men aged 18 and over can take sildenafil for erectile dysfunction. Most adults and children aged 1 year and over can take sildenafil for pulmonary hypertension. Who may not be able to take sildenafil. Sildenafil is not suitable for some people. To make sure it’s safe for you, speak to your doctor or pharmacist before taking sildenafil if you. AdComplete the Online Consultation with our Doctor. Personalize Your Needs. If Appropriate, Get a Prescription for ED from RexMD®. Free Shipping Available/5 (3, reviews)Types: Premature Ejaculation · Privacy Policy · Sexual Health.