What are the side effects of nytol?

Updated February 21, 2017

Nytol is a brand name for the medication diphenhydramine hydrochloride, which is available over-the-counter without a doctor's prescription. Despite its effectiveness at treating insomnia and helping you sleep, Nytol poses a risk for side effects in some patients.

Types of Side Effects

Side effects of Nytol include dry mouth, dizziness and prolonged drowsiness.


Because it has the potential to cause drowsiness or dizziness, do not drive or operate heavy machinery until you know how Nytol affects you.

Time Frame

Nytol is only intended for temporary use, and if taken long term, has the potential to cause severe insomnia when you stop taking Nytol, according to the Mayo Clinic.

Drug Interactions

Alcohol, the blood pressure medication metoprolol, anti-seizure drugs, sedatives, tranquillisers, muscle relaxers, narcotic pain relievers, barbiturates and MAO inhibitor antidepressants all pose an increased risk for side effects from Nytol, and the combination should be avoided.


If you have glaucoma, heart problems or an enlarged prostate, it may not be safe for you to take Nytol, warns the Mayo Clinic. In addition, Nytol should not be used by pregnant or nursing women or children under 12 years of age, and should be used in caution with patients over the age of 60.

bibliography-icon icon for annotation tool Cite this Article

About the Author

Faith Davies has been writing professionally since 1996, contributing to various websites. She holds an LAH insurance license in the state of Pennsylvania and has experience as a bank branch manager and lending officer. Davies graduated cum laude from the University of Pittsburgh with a Bachelor of Arts in art history.