Pharmacology One-Liners Antihistamines

Autacoids

A class of endogenous substances that include histamine, serotonin, prostaglandins, and vasoactive peptides that work in autocrine or paracrine manner.

Bradykinin and histamine

Peptides that increase capillary permeability and edema.

Histamine H1 receptors

Tissue distribution includes smooth muscle and mast cells.

Histamine H2 receptors

Tissue distribution includes stomach, heart, and mast cells.

Histamine H3 receptors

Tissue distribution includes nerve endings and CNS.

1st generation antihistamines

Common adverse effects include sedation and anticholinergic effects.

Diphenhydramine

1st generation antihistamine that is highly sedating.

Chlorpheniramine

1st generation antihistamine that is least sedating.

H1 antihistamines

Major indication is for IgE mediated allergic reaction (allergic rhinitis, urticaria).

Diphenhydramine

Antihistamine that is indicated for allergies, motion sickness, and insomnia.

Dimenhydrinate

Antihistamine with motion sickness as the only indication.

2nd generation antihistamines

Includes Fexofenadine, loratadine, cetirizine.

Cimetidine

H2 antagonist that causes the most interactions with other drugs.

H2 antagonists

Indications include acid reflux disease, duodenal ulcer, and peptic ulcer disease.