Diphenhydramine

Allergic diseases fall into the category of chronic diseases with a high incidence globally, and antihistamines have always been the core option for clinical symptomatic treatment. Diphenhydramine is a first-generation ethanolamine antihistamine, which inhibits allergic reactions by competitively blocking histamine H1 receptors, and also has central inhibitory, antiemetic and anti-M cholinergic effects. Clinically, it can be used for allergic diseases such as urticaria, allergic rhinitis and skin itching, and can also relieve nausea and vomiting caused by motion sickness, as well as serve as an adjuvant medication for sedation and hypnosis before and after surgery. The applicable population covers adults and children with clear medication indications.

The global market size of antihistamines has maintained steady growth in recent years, and the overall market size had exceeded 9 billion US dollars in 2023. Among them, first-generation antihistamines occupy nearly 30% of the share in the primary care and OTC markets due to their cost-effectiveness advantage. As a classic product that has been on the market for more than 70 years, the annual global demand for diphenhydramine API is stable at around 3,500 tons. China is the world's largest producer of diphenhydramine API, with production capacity accounting for more than 65% of the total global supply. The products of domestic enterprises are mainly exported to North America, Southeast Asia and European markets. The overall market competition pattern is mature, with small price fluctuations.

The original research enterprise of diphenhydramine is Pfizer Inc. of the United States, with the original brand name Benadryl, and its core compound patent expired globally in 1964. At present, the commonly used clinical dosage forms include oral tablets, injections, topical creams, etc. The conventional specifications of tablets are 25mg and 50mg, and the specification of injection is 1ml:20mg. The original research product has been included in the FDA Reference Listed Drug Catalog, and the reference listed drug included in the *China Listed Drug Catalog* domestically is the 25mg tablet held by Pfizer Pharmaceutical. 12 valid registration numbers of diphenhydramine API can be found on the domestic API registration platform, among which 10 are held by domestic enterprises, and the other 2 are imported API registrations. At present, more than 60 domestic enterprises have been approved to produce diphenhydramine-related preparations. (Data as of June 2025, please refer to the official website of CDE for the latest information)

In the process of drug R&D and quality control, impurity research is a key link to ensure the safety of APIs and preparations. CATO provides a full set of impurity standard substances for diphenhydramine API, most of which are in stock. For in-stock products, orders placed before 16:00 will be shipped on the same day. All standard substances meet the compliance requirements of multiple regulations such as the Chinese Pharmacopoeia and FDA, and can meet the full-process needs of enterprises in process optimization, quality research, registration and declaration, etc.