Chapter 189- Antihistamines

Question 1

First line therapy for chronic idiopathic and physical urticaria

Answer 1

H1 antihistamines

Question 2

Useful adjunct therapy to H1 antihistamine therapy in refractory cases of chronic idiopathic urticaria/angioedema

Answer 2

H2 antihistamines

Question 3

Histamine is metabolized by 2 major pathways (2)

Answer 3

Diamine oxidase

Histamine methyl transferase

Question 4

Inverse agonists that reversibly bind and stabilize the inactive form of H1 receptor

Answer 4

H1 antihistamines

Question 5

Second generation antihistamines have ___ lipophilicity and bind ___ hence have fewer CNS effects

Answer 5

Reduced

Selectively

Question 6

Safe for those with hepatic impairment (5)

Answer 6

Cetirizine
Levocetirizine
Desloratadine
Fexofenadine
Levocabastine

Question 7

Indications for treatment with H1 antihistamines (5)

Answer 7

Acute urticaria
Chronic idiopathic urticaria
Physical urticaria and dermographism
Pruritus associated with histamine release
Symptoms of mastocytosis

Question 8

Most commonly reported problem with first generation H1 antihistamines

Answer 8

Sedation

Question 9

All second generation antihistamines are less sedating except for (2)

Answer 9

Cetirizine

Levocetirizine

Question 10

Anticholinergic side effects are common in ff groups of antihistamines

Answer 10

Ethanolamine
Phenothiazine
Piperazine

Question 11

Most serious but rare side effects

Answer 11

Arrhythmias

Question 12

2 second gen antihistamines removed due to risk of QT interval prolongation and torsades de pointes

Answer 12

Terfenadine

Astemizole

Question 13

Contraindicated for patients receiving first generation H1 antihistamines

Answer 13

Monoamine oxidase inhibitors

Question 14

Central depressive effects are observed when 2nd gen antihistamines are combined with alcohol.
True or False

Answer 14

False, 1st gen

Question 15

Antihistamines are generally avoided during first trimester due to its association with

Answer 15

Cleft palate defects

Question 16

Antihistamines requiring adjustment for renal (3)

Answer 16

Acrivastine
Ebastine
Fexofenadine

Question 17

Antihistamines requiring adjustment for hepatic impairment (1)

Answer 17

Mizolastine

Question 18

Major features of acute poisoning in children (5)

Answer 18

Hallucinations
Ataxia
Incoordination
Athetosis
Convulsions

Question 19

First generation antihistamines are preferred for breastfeeding women.
True or False

Answer 19

False, second

Question 20

Indications for treatment with H2 antihistamines (3)

Answer 20

Acute allergic reaction
Chronic urticaria
Systemic symptoms associated with mastocytosis

Question 21

Requires dose adjustments in renal impairment (3)

Answer 21

Ranitidine
Famotidine
Nizatidine

Question 22

Uncommon side effects of cimetidine (5)

Answer 22

Gynecomastia
Galactorrhea
Loss of libido
Impotence
Reduction of sperm counts

Question 23

H2 atnihistamines that inhibit alcohol dehydrogenase activity (2)

Answer 23

Cimetidine

Ranitidine

Question 24

Cimetidine is an inhibitor and should not be taken with

Answer 24

Dofetilide
Warfarin
Phenytoin
BZD
Metformin
Sulfonylureas
SSRIs

Question 25

Uncommon side effect of H2 antihistamines to neonates

Answer 25

Necrotizing enterocolitis

Question 26

H2 antihistamines are FDA Category

Answer 26

B

Question 27

TCA most commonly used in dermatology

Answer 27

Doxepin 800 times more potent than diphenhydramine

Question 28

MC adverse effect of oral and topical doxepin

Answer 28

Sedation

Question 29

Oral doxepin is FDA Category

Answer 29

C

Question 30

Doxepin is not safe to use for children less than ___ years of age

Answer 30

12

Question 31

Benzocycloheptathiophene H1 antihistamine with mast cell and basophil stabilizing properties

Answer 31

Ketotifen