What Is Diphenhydramine?
Diphenhydramine is an organic compound, a tertiary amine with two phenyl groups and one ether group in the molecule.
It is represented by the chemical formula C17H21NO, and its CAS number is 58-73-1. It has a molecular weight of 255.355, a boiling point of 302-320°F (150~160°C) (266 Pa), and is a yellow liquid with a characteristic odor at room temperature.
The hydrochloride salt (diphenhydramine hydrochloride) is widely available on the market. This salt has a CAS number of 147-24-0, a molecular weight of 291.82, and a melting point of 332.6-340°F (167-171°C). At room temperature, it appears as a white crystal or crystalline powder and is soluble in water, ethanol, and acetic acid; somewhat insoluble in acetone; and almost insoluble in diethyl ether.
Diphenhydramine antagonizes histamine, which causes inflammation and is used as a drug to reduce inflammation, airway secretion, and sedation.
Uses of Diphenhydramine
Diphenhydramine, an antihistamine (H1 receptor antagonist), antagonizes both peripheral and central histamine, resulting in the suppression of inflammation, airway secretion, and sedation. It is effective against urticaria, pruritus, and allergic rhinitis, including hay fever, mainly using its hydrochloride form.
Its side effect of inducing drowsiness has led to its use as a sleep-improving drug. In non-clinical applications, it is sometimes used as an antihistamine in experimental studies.
Properties of Diphenhydramine
1. Synthetic Method of Diphenhydramine
Diphenhydramine is synthesized by reacting diphenylmethylbromide with N,N-dimethylethanolamine, a nucleophilic substitution reaction under basic conditions.
2. Pharmacological effects of Diphenhydramine
Diphenhydramine, an antihistamine that antagonizes histamine H1 receptors, is used to relieve allergic symptoms caused by hay fever, colds, and urticaria. One of its notable side effects is drowsiness. It is also used as a sleep aid. However, its use for insomnia and long-term continuous use is not recommended. It is contraindicated in patients with glaucoma or obstructive diseases of the lower urinary tract.
Types of Diphenhydramine
Diphenhydramine is mainly used in its hydrochloride salt form as a drug. It is an ingredient in oral cold medicines, topical ointments, and injectable drugs. Indications include allergic rhinitis, urticaria, itching associated with skin diseases, acute rhinitis, and vasomotor rhinitis. Oral use is contraindicated in glaucoma patients and patients with obstructive diseases of the lower urinary tract.
Other products include research reagents, most sold as hydrochloride salts, with capacities ranging from small to large quantities. Diphenhydramine-d6 hydrochloride, a deuterium-replaced variant, is also available, requiring refrigerated storage, and is available in various capacities.