However the dose is usually not more than 40 mg 3 times a day. If you often forget doses, it may help to set an alarm to remind you. Do not keep outdated medicine or medicine no longer needed. If used together, your doctor may change the dose or how often you use this medicine, or give you special instructions about the use of food, alcohol, or tobacco. Dosing The dose of this medicine will be different for different patients.Viagra is an effective drug for treating male erectile dysfunction, but it targets sexual performance, not sexual arousal. There is limited evidence that Viagra may be beneficial . Viagra is available in three strengths: 25 milligrams (mg), 50 mg, and mg. Medically reviewed by Last updated on Applies to the following strengths: 10 mg/mL; 10 mg/ mL; 20 mg; 25 mg; 50 mg; mg Usual Adult Dose .