ANTIHISTAMINE

Question 1

What are autacoids? Potent endogenous substances that act locally

Answer 1

with complex physiological and pathophysiological functions outside traditional immune or autonomic groups.

Question 2

What are examples of amine autacoids? Histamine and serotonin (5-hydroxytryptamine).

Question 3

What is histamine

Answer 3

and where is it stored? A ubiquitous amine formed from histidine; stored in mast cells

Question 4

What triggers histamine release? Chemical and physical agents

Answer 4

such as injury or immune responses.

Question 5

What are histamine’s effects on the cardiovascular system? Decreases systolic and diastolic blood pressure

Answer 5

increases heart rate and contractility as a reflex.

Question 6

What are histamine’s effects on the GI tract? Increases gastric acid secretion via H2 receptors; causes smooth muscle contraction.

Question 7

What are histamine’s effects on the bronchi? Causes smooth muscle contraction and secretion

Answer 7

potentially leading to bronchoconstriction (e.g.

Question 8

What are histamine’s effects on nerve endings? Causes pain and itching.

Question 9

What are toxic effects of histamine? Flushing

Answer 9

headache

Question 10

What are H1 receptor antagonists? Drugs that competitively and reversibly block H1 receptors to antagonize histamine effects

Answer 10

often divided into first and second generations.

Question 11

What are the classifications of H1 receptor antagonists? Potent sedative (e.g.

Answer 11

diphenhydramine)

Question 12

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

Answer 12

anti-nausea

Question 13

What are the anticholinergic effects of first-generation antihistamines? Dry mouth

Answer 13

urinary retention

Question 14

Why are antihistamines not used for asthma? They are not strong bronchodilators.

Question 15

What is cyproheptadine used for? Treatment of skin allergies

Answer 15

cold urticaria

Question 16

What are common side effects of antihistamines? Sedation

Answer 16

antimuscarinic effects (dry mouth

Question 17

Why do first-generation antihistamines have more side effects? They have poor selectivity for H1 receptors and block other receptors (e.g.

Answer 17

cholinergic

Question 18

What are examples of clinical uses of H1 antihistamines? Treatment of allergic rhinitis

Answer 18

urticaria

Question 19

What are drug interactions with antihistamines? 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? Terfenadine

Answer 20

loratadine

Question 21

What is the mechanism of action of H1 receptor antagonists? They block H1 receptors

Answer 21

reducing histamine-induced effects like capillary permeability

Question 22

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

Question 23

What are the pharmacodynamics of first-generation antihistamines? Block H1 receptors

Answer 23

may also block muscarinic

Question 24

What are the pharmacokinetics of antihistamines? Well-absorbed orally and parenterally

Answer 24

with significant liver metabolism and urinary excretion of metabolites.

Question 25

What are the symptoms of histamine toxicity? Flushing

Answer 25

hypotension