Drowsiness is one of the major side effects of some antihistamines, such as diphenhydramine (Benadryl) and doxylamine succinate (the antihistamine found in Nyquil). How long does Benadryl make you sleepy for? Will I still wake up drowsy after taking it and getting 7 hours of sleep? What other drugs will affect Benadryl? Ask a doctor or pharmacist before using this medicine if you are also using any other drugs, including prescription and over-the-counter medicines, vitamins, and herbal products. In the morning, consider taking a choline supplement to increase acetylcholine synthesis. There are a variety of different types of choline supplements. I recommend 600 mg of alpha-GPC (choline alfoscerate) when you wake up. It won't completely reverse the groggy hangover effects, but it will help. Sominex (diphenhydramine): They do help me sleep but I feel really terrible in the morning. Very groggy and very short tempered. Have had to throw the pack out as I feel so awful in the mornings. I've not noticed this to this degree of morning grogginess with other sleeping tablets. Horrible stuff! Human Resources for the University of Oklahoma. Serving Faculty and Staff in Norman, Oklahoma City, and Tulsa campuses. To reduce daytime drowsiness, take an antihistamine in the evening rather than in the morning: It may help you sleep, with drowsy effects wearing off by the next day. Be aware, though, that. They will usually help someone get to sleep and stay asleep most of the night without too much hangover effect the next morning. As with most prescription sleep aids, I recommend intermittent use so that tolerance and withdrawal might be avoided. Buyer Be Aware: Benadryl is a Serious Drug. This common over-the-counter drug was the precursor to Prozac. It can make you drowsy, scramble your brain, and impair your driving more than alcohol.