The trial results revealed that sildenafil had improved the patients’ depression, anxiety, and self-esteem. Read and follow these instructions carefully before you start using sildenafil and each time you get a refill of your medicine. For erectile dysfunction, it’s best to take sildenafil on an empty stomach. However, the dose is usually not more than 80 mg 3 times a day. If you experience a sudden loss of vision in one or both eyes, contact your doctor immediately. Key facts It usually takes 30 to 60 minutes for sildenafil to work for erectile dysfunction. Different brands may not work the same way. · Abnormal penis, including a curved penis or birth defects of the penis—Chance of problems occurring may be increased and this medicine should be used with caution in these patients. Angina (severe chest pain), unstable or. Arrhythmia (irregular heartbeat, within the last 6 months) or. This means that 4 hours after you take a dose, your body has cleared half of the dose. In most cases, it takes about 5 half-lives for your body to completely remove a drug from your system. So. Viagra comes as an oral tablet in different dosages. Discuss with your doctor what’s an appropriate dose for you. For daily use, Goldstein said, the generic form, sildenafil, comes in mg tablets.