If you will be taking this medicine for pulmonary arterial hypertension, your doctor will want to check your progress at regular visits. Do not keep outdated medicine or medicine no longer needed. If you experience chest pain, dizziness, or nausea during sex, seek immediate medical help. Before taking sildenafil, tell your doctor and pharmacist if you are allergic to sildenafil, any other medications, or any of the ingredients in sildenafil tablet or suspension. 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. Make sure you have discussed any other medications you are currently taking or plan to take before starting sildenafil with your doctor and pharmacist.In most males,* Viagra works within 1 hour after it’s taken. It’s possible that Viagra can begin working within 30 minutes of being taken. But other times, it may take up to 4 . Still, if your doctor says it’s okay for you to use and you end up paying out-of-pocket, you can still get the generic for a lot less than Viagra. According to price-comparison site test1.ru As an alternative to Viagra, a person may wish to try any of the following: Alternative oral drugs: Including vardenafil, tadalafil, and avanafil. Nonoral drugs: Such as penile self injections.