From Mayo Clinic to your inbox Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Males between the ages of 30 and 65 would be eligible to buy four tablets after a consultation with a pharmacist. Some potential side-effects include headache and dizziness, hot flushes, indigestion, blurred vision, and nasal congestion. Follow the manufacturer’s directions to use and clean the oral syringe. Do not keep outdated medicine or medicine no longer needed. You may take this medicine with or without food.Sildenafil tablets for erectile dysfunction come in different strengths ranging from 25mg to mg. The usual dose is 50mg, when you need it. Do not take it more than once a day. . Sildenafil works in different ways, depending on the condition it’s being used to treat. For ED: Sildenafil works by increasing blood flow to the penis. This helps .  · sores in the mouth and on the lips. tense muscles. trembling and shaking. vomiting. waking to urinate at night. worsening of asthma. Other side effects not .