Mechanism of Action

At therapeutic doses, the first- and second-generation antihistamines are equilibrium-competitive inhibitors of H1-receptor-mediated responses. Certain second-generation drugs are noncompetitive inhibitors at high concentrations. Both first- and second-generation compounds have negligible abilities to block the H2-, H3-, or H4-receptors. The therapeutic effectiveness of these

TABLE 38.2 Representative H1Receptor Antagonists

Trade Duration of Sedative Anti-Motion Anticholinergic

Drug Name Action (hr) Activity Sickness Activity Activity

First-Generation Antihistamines

Ethanolamines Carbinoxamine Clemastine Diphenhydramine Dimenhydrinate Ethylenediamines Pyrilamine Tripelennamine

Alkylamines

Chlorpheniramine Brompheniramine Piperazines Cyclizine Hydroxyzine Meclizine

Phenothiazines

Promethazine Piperidines

Cyproheptadine

Second-Generation Antihistamines

Promethazine Piperidines

Cyproheptadine

Second-Generation Antihistamines

Periactin 4-6

Piperidines

Bacterial Vaginosis Facts

Bacterial Vaginosis Facts

This fact sheet is designed to provide you with information on Bacterial Vaginosis. Bacterial vaginosis is an abnormal vaginal condition that is characterized by vaginal discharge and results from an overgrowth of atypical bacteria in the vagina.

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