Viagra (sildenafil) is used by men diagnosed with erectile dysfunction, working in the majority of all cases. Drinking alcohol and taking Viagra is generally safe, but you need to be aware of the possibility of getting the following side effects - rapid heartbeat, low blood pressure and dizziness. These side effects may occur in theory, as both Viagra and alcohol are known for their blood-dilating effects. How long Viagra will last for you depends on several important factors - for instance, if you are older than 65, have liver or kidney disease this medicine may stay in your body longer. Other factors can make Viagra less efficient or decrease its amount in the body, including taking this medicine with a high-fat meal and taking some medications, such as rifampin. If you have any questions about your treatment consult your doctor.