ANTIHISTAMINE

Question 1

What are autacoids?

Answer 1

Potent endogenous substances that act locally with complex physiological and pathophysiological functions outside traditional immune or autonomic groups.

Question 2

What are examples of amine autacoids?

Answer 2

Histamine and serotonin (5-hydroxytryptamine).

Question 3

What is histamine and where is it stored?

Answer 3

A ubiquitous amine formed from histidine; stored in mast cells

Question 4

What triggers histamine release?

Answer 4

Chemical and physical agents such as injury or immune responses.

Question 5

What are histamine’s effects on the cardiovascular system?

Answer 5

Decreases systolic and diastolic blood pressure increases heart rate and contractility as a reflex.

Question 6

What are histamine’s effects on the GI tract?

Answer 6

Increases gastric acid secretion via H2 receptors; causes smooth muscle contraction.

Question 7

What are histamine’s effects on the bronchi?

Answer 7

Causes smooth muscle contraction and secretion potentially leading to bronchoconstriction (e.g.

Question 8

What are histamine’s effects on nerve endings?

Answer 8

Causes pain and itching.

Question 9

What are toxic effects of histamine?

Answer 9

Flushing
headache

Question 10

What are H1 receptor antagonists?

Answer 10

Drugs that competitively and reversibly block H1 receptors to antagonize histamine effects often divided into first and second generations.

Question 11

What are the classifications of H1 receptor antagonists?

Answer 11

Potent sedative (e.g. diphenhydramine)

Question 12

What pharmacological actions are associated with first-generation H1 antihistamines?

Answer 12

Sedation
anti-nausea

Question 13

What are the anticholinergic effects of first-generation antihistamines?

Answer 13

Dry mouth
urinary retention

Question 14

Why are antihistamines not used for asthma?

Answer 14

They are not strong bronchodilators.

Question 15

What is cyproheptadine used for?

Answer 15

Treatment of skin allergies
cold urticaria

Question 16

What are common side effects of antihistamines?

Answer 16

Sedation antimuscarinic effects (dry mouth

Question 17

Why do first-generation antihistamines have more side effects?

Answer 17

They have poor selectivity for H1 receptors and block other receptors (e.g. cholinergic

Question 18

What are examples of clinical uses of H1 antihistamines?

Answer 18

Treatment of allergic rhinitis urticaria

Question 19

What are drug interactions with antihistamines?

Answer 19

Increased sedation with alcohol or other sedatives; liver enzyme inhibitors increase arrhythmia risk with some second-generation antihistamines.

Question 20

What are examples of second-generation non-sedative antihistamines?

Answer 20

Terfenadine
loratadine

Question 21

What is the mechanism of action of H1 receptor antagonists?

Answer 21

They block H1 receptors reducing histamine-induced effects like capillary permeability

Question 22

How are antihistamines metabolized?

Answer 22

Primarily metabolized in the liver; degradation products are excreted in urine.

Question 23

What are the pharmacodynamics of first-generation antihistamines?

Answer 23

Block H1 receptors may also block muscarinic

Question 24

What are the pharmacokinetics of antihistamines?

Answer 24

Well-absorbed orally and parenterally with significant liver metabolism and urinary excretion of metabolites.

Question 25

What are the symptoms of histamine toxicity?

Answer 25

Flushing
hypotension