The active ingredient in Unisom is diphenhydramine hydrochloride [1]. This ingredient is an antihistamine that can cause drowsiness, which is why it is used in sleep aids [1][2].
What is diphenhydramine hydrochloride?
Diphenhydramine hydrochloride is a first-generation antihistamine belonging to the ethanolamine class [1][3]. It works by blocking the action of histamine, a substance in the body that causes allergy symptoms [1]. Its sedating effect is a primary mechanism by which it aids in sleep [2].
What other products contain diphenhydramine hydrochloride?
Besides Unisom, diphenhydramine hydrochloride is the active ingredient in many other over-the-counter products, including Benadryl, ZzzQuil, and various generic allergy and cold medications [4][5].
How does diphenhydramine hydrochloride work as a sleep aid?
Diphenhydramine hydrochloride's sedative properties are a result of its ability to cross the blood-brain barrier and affect the central nervous system [2]. It binds to H1 histamine receptors in the brain, which are involved in regulating the sleep-wake cycle, leading to drowsiness [2][3].
What are the side effects of diphenhydramine hydrochloride?
Common side effects of diphenhydramine hydrochloride include dry mouth, blurred vision, constipation, and urinary retention [1][3]. Drowsiness is a primary intended effect but can be considered a side effect when used for purposes other than sleep [1][2]. Cognitive impairment and anticholinergic effects are also associated with its use [3].
Are there different types of Unisom?
Yes, Unisom offers different formulations, and some contain different active ingredients than diphenhydramine hydrochloride. For example, Unisom SleepGels contain doxylamine succinate, another antihistamine with sedative properties [6]. It is important to check the active ingredient listed on the product packaging to confirm what is in a specific Unisom product [6].
When does the patent for diphenhydramine expire?
Diphenhydramine hydrochloride is a very old drug and has long been off-patent [4]. Its original patents expired many decades ago, making it widely available as a generic medication.
What are the alternatives to diphenhydramine for sleep?
Alternatives to diphenhydramine for sleep include other antihistamines like doxylamine succinate, as well as other classes of medications. Non-pharmacological approaches such as cognitive behavioral therapy for insomnia (CBT-I) and good sleep hygiene practices are also recommended [7].
Sources:
1. https://www.drugpatentwatch.com/search?q=diphenhydramine+hydrochloride
2. https://www.ncbi.nlm.nih.gov/books/NBK470341/
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4317633/
4. https://pubmed.ncbi.nlm.nih.gov/26943653/
5. https://www.ncbi.nlm.nih.gov/books/NBK538255/
6. https://www.unisom.com/products/
7. https://www.sleepfoundation.org/insomnia/treatment/what-is-cognitive-behavioral-therapy-for-insomnia