This produces the unwanted side effect of sedation.
Nonselective topical antihistamines include pheniramine, antazoline, chlorpheniramine, and cyclizine.
Some of the more commonly available first-generation antihistamines used in veterinary and human medicine include brompheniramine (Dimetane), chlorpheniramine (Chlor-Trimeton), clemastine (Tavist), cyproheptadine (Periactin), dimenhydrinate (Dramamine), diphenhydramine (Benadryl), hydroxyzine (Atarax), meclizine (Antivert), promethazine (Phenergan), trimeprazine (Temaril), and tripelennamine (PBZ).
1,2 Second-generation antihistamines lack the sedative properties of first generation antihistamines and include astemizole (Himanal), cetirizine (Zyrtec), fexofenadine (Allegra), loratadine (Claritin), and terfenadine (Seldane).
Although typical people use the word “antihistamine” to describe drugs for treating allergies, doctors and scientists use the term to describe a class of drug that opposes the activity of histamine receptors in the body.-receptor are used to treat allergic reactions in the nose (e.g., itching, runny nose, and sneezing) as well as for insomnia.