Antihistamines

Question 1

How is histamine formed

Answer 1

Synthesized in tissues by decarboxylation of the amino acid 1-histidine

Question 2

Where is histamine stored

Answer 2

In the tissues (mast cells, gastric mucosa and neurons) and in the blood (basophils)

Question 3

Where is histamine rapidly replenished

Answer 3

in the CNS (neurons) and stomach

Question 4

where is histamine slowly replenished

Answer 4

mast cells and basophils

Question 5

What is the triple response of Lewis

Answer 5

Localized red spot within seconds, bright red flash developing more slowly, and wheal within minutes occupies the same area as red spot

Question 6

What causes the localized red spot (mm) in the triple response of Lewis

Answer 6

vasodilation (H1 in the endothelium)

Question 7

What causes the brighter red flush in the triple response of lewis

Answer 7

histamine stimulation of axon reflexes causing indirect vasodilation

Question 8

what causes the wheal in the triple response of lewis

Answer 8

histamine’s ability to increase capillary permeability (edema)

Question 9

Where is the H1 receptor found

Answer 9

SM, endothelium, and CNS tissue

Question 10

Where is the H2 receptor found

Answer 10

On parietal cells

Question 11

Where is the H3 receptor found

Answer 11

CNS and some peripheral nervous system tissue

Question 12

Where is the H4 receptor found

Answer 12

Primarily in basophils and in bone marrow; also the thymus, small intestine and colon and spleen

Question 13

This histamine receptor’s function is to cause vasodilation, bronchoconstriction, SM contraction, which are all immediate events of allergic response

Answer 13

H1

Question 14

This histamine receptor’s function is to stimulate gastric acid secretion

Answer 14

H2

Question 15

This histamine receptor’s function is decreased NT release: histamine, Ach, NE, serotonin; counteract the effect of histamine

Answer 15

H3

Question 16

This histamine receptor’s function plays a role in chemotaxis; get mast cell chemotaxis and leukotriene productions (all about inflammation)

Answer 16

H4

Question 17

What are the 3 localized cutaneous responses of histamine

Answer 17

Erythema, urticaria (increased permeability=edema and erythema: hive/wheals), and Pruritus

Question 18

Itchiness and pain is caused by sensitization of afferent nerve terminals due to which histamine receptor

Answer 18

H1

Question 19

What are the 3 strategies to inhibit histamine action

Answer 19

Administer antihistamines, counteract the effects of histamine (epi) and mast cell stabilizers

Question 20

What do mast cell stabilizers do

Answer 20

prevents release of histamine from mast cells

Question 21

This is used in the treatment of allergic rhinitis, conjunctivitis, and asthma

Answer 21

Mast cell stabilizers

Question 22

Cromolyn sodium and Nedocromil

Answer 22

Mast cell Stabilizers

Question 23

1st generation are reversible, competitive antagonist against which histamine receptor

Answer 23

H1

Question 24

What is a problem with first generation H1 receptor blockers drugs

Answer 24

Will cross the BBB and placenta; cause sedation, tachycardia

Question 25

Diphenhydramine, hydroxyzine, cyclizing, dimenhydrinate, meclizine, promethazine

Answer 25

1st generation H1 receptor antagonist

Question 26

Why are 2nd generation H1 receptor antagonists more useful

Answer 26

they are non-sedating anti-allergy therapeutics

Question 27

What is an adverse effect of 2nd generation H1 receptor antagonists

Answer 27

Cetirizine induces more CNS actions than other 2nd generation drugs; not recommended for pilots

Question 28

Which 2nd generation H1 antagonists are excreted mainly in the unmetabolized form in the urine/feces

Answer 28

Cetirizine, Loratadine, Fexofenadine

Question 29

What do 2nd generation H1 receptor drugs end in

Answer 29

-adine, except for cetirizine

Question 30

What do the H2 receptor antagonists end in

Answer 30

-Tidine (cimetidine, Famotidine, and Ranitidine)