Other Uses This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. Talk to your pharmacist for more details. This does not include the cost of your medication if prescribed. Many people using this medication do not have serious side effects. Terms and conditions of use. Do not take this medication with any other product that contains sildenafil or other similar medications for erectile dysfunction-ED or pulmonary hypertension such as tadalafil, vardenafil.Checking the legitimacy of your online pharmacy. Two ways you can check if your online pharmacy is legitimate: For sites listing a Canadian street address, check with the pharmacy regulatory authority for that province or territory to see if the pharmacy is licensed. For example, if the site provides a Quebec address as its pharmacy. You may report side effects to Health Canada at Precautions Before taking sildenafil, tell your doctor or pharmacist if you are allergic to it; or if you have any other. Viagra is one of the world’s most counterfeited medicines. According to a Pfizer study, around 80% of sites claiming to sell Viagra were selling counterfeits. Regional issues Brazil. Pfizer’s patent on sildenafil citrate expired in Brazil in Canada.