Viagra 100 mg is a prescription medicine used primarily to treat erectile dysfunction (ED) by increasing blood flow to the penis. It contains the active ingredient Sildenafil and is typically taken about one hour before planned sexual activity. 
 
Key Usage Details
Timing: Best taken 1 hour before sex, though it can work as quickly as 30 minutes and remains effective for 4–5 hours.
Sexual Stimulation: The tablet does not cause an erection on its own; physical or mental arousal is required for it to work.
Frequency: Do not take more than one dose in a 24-hour period.
Food: Can be taken with or without food, but a heavy or high-fat meal may delay the onset of action.