Anti_Histamines

Question 1

Autacoids

Answer 1

endogenous molecules that do not fall into traditional autonomic groups. They do not act on cholinoceptors
or adrenoceptors but have powerful pharmacologic effects on
smooth muscle and other tissues.

Question 2

Most important amine autacoids

Answer 2

Histamine and Serotonin (5-hydroxytryptamine, 5-HT)

Question 3

Acid-peptic disease

Answer 3

The disease of the upper digestive tract caused by acid and pepsin; includes gastroesophageal reflux,
erosions, and ulcers

Question 4

Carcinoid

Answer 4

A neoplasm of the gastrointestinal tract or bronchi that may secrete serotonin and a variety of peptides

Question 5

Ergotism (“St. Anthony’s

fire”)

Answer 5

Disease caused by excess ingestion of ergot alkaloids; classically an epidemic caused by consumption of grain (eg, in bread) that is contaminated by the ergot fungus

Question 6

Gastrinoma

Answer 6

A tumor that produces large amounts of gastrin; associated with hypersecretion of gastric acid and pepsin leading to ulceration

Question 7

IgE-mediated immediate

reaction

Answer 7

An allergic response, for example, hay fever or angioedema, caused by interaction of an antigen
with IgE antibodies on mast cells; results in the release of histamine and other mediators of allergy

Question 8

Oxytocic

Answer 8

A drug that causes contraction of the uterus

Question 9

Zollinger-Ellison syndrome

Answer 9

Syndrome of hypersecretion of gastric acid and pepsin, often caused by gastrinoma; is associated
with severe acid-peptic ulceration and diarrhea

Question 10

Histamine is synthesized by

Answer 10

Histidine

Question 11

Where is histamine stored?

Answer 11

stored in high concentrations in vesicles in mast cells, enterochromaffin cells in the gut, some neurons, and a few other cell types

Question 12

Histamine is metabolized by the enzymes

Answer 12

monoamine oxidase

and diamine oxidase.

Question 13

Excess production of histamine in the body

Answer 13

systemic mastocytosis

Question 14

How is systemic mastocytosis measured?

Answer 14

detected by measurement of its major metabolite, imidazole acetic acid, in the urine. Because
it is released from mast cells in response to IgE-mediated (immediate) allergic reactions,

Question 15

the pathophysiologic role of Histamine

Answer 15

plays a pathophysiologic role in seasonal rhinitis (hay fever), urticaria, and angioneurotic edema. (The peptide bradykinin also plays an important role in
angioneurotic edema

Question 16

scombroid poisoning

Answer 16

Fish that has been stored improperly
generates high concentrations of histamine; consumption of
such fish may produce severe histamine toxicity

Question 17

receptors that have most Histamine actions

Answer 17

H1 and H2

Question 18

triple response

Answer 18

histamine effect on the skin is mediated mainly by H1 and H2
receptors. This response involves a small red spot at the center of an intradermal injection of histamine surrounded by an edematous wheal, which is surrounded by a red flare.

Question 19

H1

Answer 19

Smooth muscle, endothelium, brain Gq; ↑ IP3, DAG

Typical responses include pain and
itching in the skin, bronchoconstriction, and vasodilation, the latter caused by the histamine-evoked release of nitric oxide. Capillary endothelial cells, in addition to releasing nitric oxide (NO) and other vasodilating substances, also contract, opening gaps in the permeability barrier and leading to the formation of local edema.
These effects occur in allergic reactions and in mastocytosis

Diphenhydramine, loratidine

Question 20

H2

Answer 20

Stomach, heart, mast cells, brain Gs; ↑ cAMP Cimetidine

This Gs-coupled receptor mediates gastric acid secretion by parietal cells in the stomach. It also has a cardiac stimulant effect. A third action is to reduce histamine release from mast cells—a negative feedback effect.

Question 21

H3

Answer 21

Nerve endings, CNS Gi; ↓ cAMP
Clobenpropit

presynaptic modulation of histaminergic neurotransmission in the central nervous system (CNS). Food intake and body weight increase in H3-receptor knockout animals; therefore,
selective H3 agonists are under investigation as appetite suppressants. In the periphery, it appears to be a presynaptic heteroreceptor with modulatory effects on the release of another transmitter

Question 22

H4

Answer 22

Leukocytes, CD4-T cells Gi; ↓ cAMP
Thioperamide

is located on leukocytes (especially eosinophils) and mast cells and is involved in chemotactic responses by these cells

Question 23

5-HT1D/1B

Answer 23

Brain

Gi; ↓ cAMP

Question 24

5-HT2

Answer 24

Smooth muscle, platelets, brain Gq; ↑ IP3, DAG Ketanserin

Question 25

5-HT3

Answer 25

Area postrema (CNS), sensory and 
enteric nerves
Ligand-gated Na+/K+channel 

Ondansetron

Question 26

5-HT4

Answer 26

Presynaptic nerve terminals in the
enteric nervous system
Gs; ↑ cAMP

Tegaserod (partial agonist)

Question 27

H1 blockers, first-generation

Answer 27

Diphenhydramine, dimenhydrinate
Competitive pharmacologic 
block of peripheral and CNS H1
receptors plus α- and M-receptor 
block. Anti-motion sickness effect

Hay fever, angioedema, motion sickness • used orally as OTC sleep aid; used parenterally for dystonias
Oral, parenteral
Duration: 6–8 h

Sedation, autonomic block Rare CNS excitation

Question 28

Promethazine:

Answer 28

H1 blocker with less anti-motion sickness action and more sedative and autonomic effects

Question 29

Cyclizine, meclizine

Answer 29

H1 blockers with more anti-motion sickness action and less sedative and autonomic effect

Question 30

Chlorpheniramine

Answer 30

H1 blocker with negligible anti-motion sickness, sedative, and autonomic effects

Question 31

H1 blockers, second generation

Answer 31

Cetirizine

Competitive pharmacologic block of peripheral H1 receptors.

No autonomic or anti-motion sickness effects

Hay fever, angioedema Oral
Duration: 12–24 h

Minimal toxicities

Question 32

Fexofenadine, loratadine, desloratadine

Answer 32

similar to cetirizine

Question 33

H2 blockers

Answer 33

Cimetidine, famotidine, ranitidine, nizatidine

Competitive pharmacologic block. No H1, autonomic, or anti-motion effects

Gastroesophageal reflux disease, stress ulcers

Oral, parenteral Duration (large doses):
12–24 h

Cimetidine: drug interactions;
other H2 blockers much less

Question 34

5-HT1 agonists

Answer 34

Sumatriptan

5-HT1D/1B agonist • causes vasoconstriction • modulates neurotransmitter release

Migraine and cluster headache

Oral, inhaled,
parenteral

Duration: 2–4 h

Paresthesias, dizziness, chest
pain • possible coronary
vasospasm

Question 35

Almotriptan, eletriptan, frovatriptan, naratriptan, rizatriptan, zolmitriptan

Answer 35

very similar to sumatriptan; oral preparations only; durations: 2–27 h