If you mean Vidalista (tadalafil) for erectile dysfunction, the appropriate strength depends on whether you want occasional or daily treatment. Vidalista 10 mg — the usual starting dose when taken as needed for many adults. Vidalista 20 mg — generally considered when 10 mg isn't effective enough and is tolerated; it isn't automatically the better choice. Vidalista 5 mg — commonly used for once-daily treatment Vidalista appropriate patients. Tadalafil can work for up to about 36 hours, so it doesn't mean you will have an erection continuously—it helps you get an erection when sexually stimulated. Do not take Vidalista/tadalafil with nitrates (such as nitroglycerin or isosorbide) or riociguat; the combination can dangerously lower blood pressure. If you tell me your age, whether you take any heart/BP medicines, and whether you're considering 5, 10, or 20 mg, I can help you determine which option is generally safest for your situation.