Allergy: Histamines and Antihistamines

Question 1

What is an allergy?

Answer 1

disorder of the immune system resulting in excessive histamine release

Question 2

What are some common allergic reactions?

Answer 2

eczema, hives, asthma, hay fever

Question 3

What are the 1st generation of antihistamines?

Answer 3

chlorpheniramine, diphenhydramine, hydroxyzine

high drowsy children

Question 4

What are the 2nd generation of antihistamines?

Answer 4

cetirizine, azelastine, loratadine, fexofenadine (CALF)

Question 5

What are autocoids produced by?

Answer 5

neural and non-neural tissues

Question 6

What is included in autocoids?

Answer 6

histamines, serotonin, prostaglandins, leukotrienes

Question 7

What is histamine released in response to?

Answer 7

injury and allergic reaction

Question 8

What can a high conc. of histamine lead to?

Answer 8

anaphylactic shock

Question 9

Histamines come from what amino acid?

Answer 9

histidine

Question 10

What enzyme is responsible for the formation of histamines?

Answer 10

L-histidine decarboxylase

Question 11

What stimuli is released during the release of histamines?

Answer 11

increase the cGMP which will increase histamine

Question 12

Histamine is an agonist for what receptor?

Answer 12

G-protein coupled receptors

Question 13

What is histamine metabolized by?

Answer 13

N-methyltransferase

Question 14

What site does an agonist have affinity for?

Answer 14

active site

Question 15

What is the role of H1 receptors?

Answer 15

involved in allergic reactions causing dermatitis, rhinit, conjunctivitis

Question 16

What results from H1 receptors?

Answer 16

1. vasodilation: decrease in blood pressure
2. increase vascular permeability
3. nerve ending cause pruritus and lungs initiates the cough reflex
4. bronchoconstriction

Question 17

Antihistamines are what type of agonists for the H1 receptor?

Answer 17

inverse agonist

shifts equil. to inactive

Question 18

Which generation of antihistamines can cross the BBB?

Answer 18

first gen

Question 19

Is the 2nd generation of antihistamines sedative?

Answer 19

NO

Question 20

Why is the first general distributed across the BBB?

Answer 20

due to higher lipid solubility

Question 21

How are antihistamines eliminated?

Answer 21

metabolized in the liver by N-methyltransferase

Question 22

Since antihistamines are inverse agonist, what site do they have affinity for?

Answer 22

inactive site

Question 23

How do antihistamines affect the block production of cGMP?

Answer 23

decrease it

Question 24

What are 1st generation of antihistamines used for?

Answer 24

allergic rhinitis, nausea, vomiting, and sedation

Question 25

What are 1st generation of antihistamines used to prevent?

Answer 25

motion sickness and vertigo

Question 26

What are 2nd generation of antihistamines used for?

Answer 26

treat allergies

Question 27

What are side effects of 1st generation antihistamines?

Answer 27

dry mouth, tachycardia, blurred vision, urinary retention ## Footnote diphenhydramine can block muscarinic receptors

Question 28

What are side effects of 2nd generation antihistamines?

Answer 28

azelastine causes dizziness, headache, nasal irritation, dry-mouth, weight gain