Histamine

Question 1

What are some major histamine-producing cells?

Answer 1

Mast cell
Basophill
ECL cell
Histaminergic neuron

Question 2

Antihistamines acting at H1 in the CNS can lead to:

Answer 2

1. Antiemetic effects
2. Sedation
3. Impaired cognition, memory and psychomotor function

Question 3

What are the different types of Histamine receptors and their functions?

Answer 3

H1: allergic inflammation
H2: secretion of gastric acid
H3: neurotransmission
H4: immunomodulation

Question 4

What are some pathphysiological actions of histamine?

Answer 4

Smooth muscle contraction (bronchoconstriction)
Vasodilation
Increase vascular permeability
stimulation ofgastric acid secretion
snsory neuron to mediate pain and itch
immunomodulation

Question 5

Allergens trigger mast cell degranulation by…

Answer 5

Cross-linking FcεR1-bound IgEs (Fc epsilon RI)

Question 6

The triple vascular response of Lewis includes

Answer 6

Flush, Flare and Wheal

Question 7

Histamine triggers the formation of a wheal (a raised swelling on the skin) due to increased…

Answer 7

Vascular permeability

Question 8

Histamine triggers the formation of a flush and flare due to…

Answer 8

Dilation of blood vessels and disruption of capillaries

Question 9

In terms of agonist or antagonist activity, what kind of drugs are clinically used as antihistamine drugs?

Answer 9

Inverse agonists

Question 10

What are the 1st generation of antihistamine?

Answer 10

Chlorpheniramine
Triprolidine
Ketotifen
Diphenhydramine
Promethazine

Question 11

which receptors do first generation H1 antihistamines targets?

Answer 11

Muscarinic Cholinergic, alpha-adrenergic, serotonin, H1

Question 12

List at least THREE examples of 2nd generation antihistamines

Answer 12

Cetirizine, Loratadine, Fexofenadine

Question 13

List at least TWO examples of drugs sometimes considered 3rd or new generation antihistamines

Answer 13

Levocetirizine, Desloratadine

Question 14

Which second-generation antihistamine is most likely to still cause some sedation?

Answer 14

Cetirizine are less sedating that first-generation antihistamines but still notably more sedating than fexofenadine and loratadine.

Question 15

Why do 2nd generation antihistamines cross the blood-brain barrier (BBB) less?

Answer 15

2nd generation antihistamines are less lipophilic and/or have greater affinity for the P‐glycoprotein efflux pump than 1st generation antihistamines

Question 16

which 1st gen h1 antihistamine can be used to treat motion sickness?

Answer 16

Diphenhydramine

Question 17

List at least THREE adverse effects of first-generation antihistamines

Answer 17

Sedation, dry mouth, GIT disturbances with nausea and vomiting

Question 18

What is one effect of 1st gen H1 antihistamine on the CNS?

Answer 18

Decrease neurotrasmission

Question 19

What is the duration of action of MOST 2nd generation antihistamines?

Answer 19

12 to 24 hours

Question 20

What is the duration of action of MOST 1st generation antihistamines?

Answer 20

4 to 6 hours

Question 21

what is the difference in specificity of 1st and new gen antihistamine

Answer 21

old gen: low h1 receptor selectivity
new gen: high h1 specificty

Question 22

Why is topical application of antihistamine generally avoided?

Answer 22

Can induce contact dermatitis
Can induce systemic allergy to the antihistamine drugs

Question 23

What are some contraindictation of antihistamine?

Answer 23

1. Do not combine with otehr CNS depressants (Alcohol,opioid,antidepressant)
2. Do not use late in 3rd trimester of pregnancy
3. Do not use when breast feeding
4. Do not use first gen H1 antihistamine in closed angle glaucoma
5. Elderly patients are particularly susceptible to CNS effects, anticholinergic effects and postural hypotension

Question 24

Use of promethazine is contraindicated in children under the age of 2 years old because of increased risk of…

Answer 24

Respiratory depression

Question 25

What must be noted when taking fexofenadine?

Answer 25

Avoid fruit juice from 4 hours before to 1-2 hours aftr dosing
Fruit juice affect absorption