Taking Viagra before falling asleep is generally not recommended. Viagra is designed to help men achieve and maintain an erection when sexually aroused. Its effects typically begin within 30 to 60 minutes and can last for up to four hours. However, taking Viagra and then going to sleep might not make the best use of the medication’s effects.
If you take Viagra and fall asleep, you might miss the window during which the medication is most effective. Additionally, Viagra can cause some side effects, such as headaches or dizziness, which could disrupt your sleep. It's best to take Viagra when you plan to engage in sexual activity and are awake to experience its benefits fully.
It is better to take viagra, before starting your sexual intercourse performance with your partner than before falling asleep.