Make sure you have discussed any other medications you are currently taking or plan to take before starting sildenafil with your doctor and pharmacist. Liquid sildenafil will usually be made up for you by your pharmacist. Do not take it more than 3 times a day. If you are taking sildenafil for erectile dysfunction, your doctor will probably start you on an average dose of sildenafil and increase or decrease your dose depending on your response to the medication. Do not stop taking sildenafil without talking to your doctor. Tell your doctor if sildenafil is not working well or if you are experiencing side effects. Because Viagra has not been studied in patients with severe liver disease, hypotension low blood pressure , recent stroke or myocardial infarction heart attack , or a hereditary eye disease, such as retinitis pigmentosa, these patients must not use it.VIAGRA is available by prescription only in 25 mg, 50 mg, and mg tablets. Not actual size. TIPS FOR TAKING VIAGRA. Take VIAGRA exactly as your doctor tells you to take it. Tell all your healthcare providers that you take VIAGRA. If you need emergency medical care for a heart problem, it will be important for your healthcare provider to. Men will no longer require a prescription to obtain the impotence drug Viagra and will instead be able to buy it over the counter at pharmacies. The decision by the UK Medicines and Healthcare. If you buy sildenafil for erectile dysfunction, it can also be known by the brand names Viagra, Aronix, Liberize and Nipatra. Sildenafil for pulmonary hypertension can also be known by the brand names Revatio and Grandipam. This medicine is available on prescription and you can also buy it from most pharmacies.