ANTIHISTAMINES

Indications

The antihistamines appear to block peripheral stimulation of the emetic center. They are therefore most ef-fective in motion sickness and inner ear dysfunction, as is seen in Ménière’s syndrome, labyrinthitis, and streptomycin ototoxicity. Dimenhydrinate, diphenhydramine, and meclizine hydrochloride are the three antihistamines primarily used in the prevention of nausea from inner ear stimulation.

Biological Functions

Several H1 histamine antagonists (e.g., diphenhydramine, promethazine, and hydroxyzine) have been used as sedative–hypnotics, since they produce some degree of sedation.While this sedation is usually considered a side effect of their antihistaminic activity, in some cases the sedation is sufficient to allow the drugs to be used in the treatment of anxiety and sleep disturbances. For these drugs, the anxiolytic properties are thought to be a direct consequence of their ability to produce sedation.
Hydroxyzine hydrochloride (Atarax, Vistaril) is the antihistamine with the greatest use in the treatment of anxiety. It is often used to reduce the anxiety that is associated with anesthesia and surgery. It also produces sedation, dries mucous membranes (via an anticholinergic mechanism), and has antiemetic activity.

Raw materials

Preparation Products