Chapter 73: Antihistamines

Question 1

Histamine function

Answer 1

• dilates small blood vessels in the vascular system
• constricts smooth muscles in the bronchi
• stimulates acid secretion in the stomach

Question 2

Histamine is

Answer 2

a neurotransmitter in the CNS

Question 3

histamine is present

Answer 3

in almost all tissues; especially skin, lungs and GI

Question 4

histamine has an important role in

Answer 4

• allergic reactions
• regulation of gastric secretions

Question 5

histamine is stored in

Answer 5

mast cells and basophils in the periphery

Question 6

histamine is produced by

Answer 6

neurons in the CNS

Question 7

histmain release can be

Answer 7

• allergic
• nonallergic

Question 8

allergic release of histamine requires

Answer 8

prior exposure to the allergen

Question 9

nonallergic release of histamine can be due to

Answer 9

several agents (certain drugs, radiocontrast media, plasma expanders)

Question 10

H1 receptors functions

Answer 10

• vasodilation
• increased capillary permeability (edema)
• bronchoconstriction
• CNS effects (cognition, memory, sleep-wake cycles)
• itching, pain, secretion of mucus

Question 11

H2 receptors functions

Answer 11

• secretion of gastric acid by acting directly on parietal cells

Question 12

what is the principle use of h1 blockers

Answer 12

treatment of mild allergic disorders
- rhinitis, itching, localized edema (h1 receptors)

Question 13

what is the principle use of H2 blockers

Answer 13

treatment of gastric and duodenal ulcers

Question 14

H1 antagonists

Answer 14

• blockage of H1 receptors
• used for treatment of mild allergic disorders

Question 15

H2 antagonists

Answer 15

• blockage of H2 receptors
• used for treatment of gastric and duodenal ulcers

Question 16

what are the H1 antagonist prototypes

Answer 16

• Diphenhydramine (benadryl) –> first generation
• Cetirizine (reactine) –> second generation

Question 17

first generation H1 antagonists are

Answer 17

highly sedating

Question 18

H1 antagonists therapuetic uses

Answer 18

• mild allergy
• severe allergy
• motion sickness
• insomnia
• common cold

Question 19

H1 antagonists adverse effects

Answer 19

• sedation
• nonsedative CNS effects (dizziness, fatigue, coordination problems, confusion)
• GI effects (nausea, vomiting, loss of appetite, constipation)

Question 20

what are the sings of toxicity for H1 antagonists

Answer 20

• dilated pupils, flushed face, hyperpryexia, dry mouth, urinary retention
• coma, cardivoascular collapse, death

Question 21

treatment for overdose of H1 antagonists

Answer 21

• activated charcoal
• cathartic
• Sezuires: IV bensodiazepines (lorazepam, midazolam)

Question 22

antihistamines are contradicted in

Answer 22

• thired trimester of pregnancy
• nuring mothers
• newborn infants

Question 23

What are the examples of second generation H1 antagonists

Answer 23

• Cetirizine (reactine)
• Fenofexadine (allegra)
• Loratadine (Claritin)
• Desloratadine (Aerius)

Question 24

benefits of second generation H1 antagonists

Answer 24

• produce much less sedation