Vidalista 40, which contains tadalafil, is used to treat erectile dysfunction. Its effects can last up to 36 hours after taking the pill, which is one of the reasons it's often referred to as the "weekend pill." It usually starts working within 30 minutes to an hour. The erectile response can be enhanced during this time if sexual stimulation occurs. It's generally effective with or without food, although a heavy meal may delay its onset.