Antihistamines

Question 1

histamine: describe it’s varied effects, where it is stored and what happens in allergic release

Answer 1

histamine is present in all tissues

effects: dilates small blood vessels, increases capillary permeability, produces constriction of smooth muscle, secretion of stomach acid, neurotransmitter in CNS.

In an allergic response, histamine interacts with nerves to promote itching, constricts muscles in the lungs, and causes vomiting and diarrhea.

Question 2

contrast the effect of H1 receptor stimulation with H2 receptor

Answer 2

H1
Vasodilation (warm, flushed skin)–>Increased capillary permeability–> Endothelial cells contract and create openings and fluids, protein platelets escape
Bronchoconstriction (Does not cause asthma)
Central nervous system (CNS) effects
Cognition, memory, sleep/waking and suppress seizures
Other–Nerves: itching, pain, mucous secretion

H2: Stimulation of the histamine H2 receptor causes accumulation of cAMP or adenylate cyclase in the brain In vascular smooth muscles, histamine H2 receptor stimulation induces relaxation.

Question 3

regarding H1 antagonists: list MOA, main drug effects and clinical uses. Use Benadryl as a prototype.

Answer 3

MOA: Histamine H1 receptor antagonists work by blocking the histamine H1 receptor

main drug effects: Drowsiness, dizziness, constipation, stomach upset, blurred vision, or dry mouth/nose/throat may occur.

clinical uses: