Ch 37 Histamine

What are autacoids

Medication classification

Group of endogenous compounds that are formed by the tissues they act on

Ex: histamine

what is histamine

Chemical messenger that functions as a NT responsible for various cellular actions, including allergic and inflammatory reactions, secretion of gastric acid, and NT in brain.

What is the role of H1 receptors

Mediate smooth muscle contraction and increase capillary permeability.

Responsible for symptoms of allergic rhinitis, atopic dermatitis, conjunctivitis, urticaria, bronchoconstriction, asthma, anaphylaxis

What is the role of H2 receptors

Located in gastric mucosa. Mediate acid production by gastric parietal cells

H3 receptor antagonists (name + use)

Pitolisant, ciproxifan

Modulate histamine in CNS and are used in narcolepsy and cognitive disorders

General uses of antihistamines

Antiallergic, anti pruritic, anti ulcer, antiemetic, anti vertigo, sedative, anxiolytic.

H1 antihistamine uses

Allergic and inflammatory conditions (allergic rhinitis, urticaria)

Allergic conjunctivitis

Motion sickness

Nausea

Sedation

Insomnia (not first line)

H1 antihistamine names

Diphenhydramine

Hydroxyzine

Mclizine

Promethazine (Phenergan)

H2 antihistamine uses + names

Treatment of ulcers and heartburn

Cimetidine, famotidine