Antihistamines

Question 1

chlorpheniramine

Answer 1

1st generation H1 antihistamine
MOA: reversibly bind to receptor and stabilize inactive form
Use: allergic rhinitis and other allergic conditions
Effects: moderately sedating and antimuscarinic activity; NO antiemetic or antimotion sickness actions
Drug interactions: MAOI prolong/intensify anticholinergic effects; additive sedative effects with sedatives; additive anticholinergic effects

Question 2

diphenhyramine (Benadryl)

Answer 2

1st generation H1 antihistamine
MOA: reversibly bind to receptor and stabilize inactive form
Use: allergic rhinitis, allergic conjunctivitis, urticaria, cough suppressant, relief of motion sickness, reduce extrapyramidal reactions, acute dystonic reactions (parenterally), local anesthetic effects (block Na+ channels)
Effects: significant sedative, antimuscarinic, and antimotion sickness actions
Drug interactions: MAOI prolong/intensify anticholinergic effects; additive sedative effects with sedatives; additive anticholinergic effects

Question 3

pyrilamine

Answer 3

1st generation H1 antihistamine
MOA: reversibly bind to receptor and stabilize inactive form
Use: allergic rhinitis and other allergic conditions
Effects: low to moderate sedation, very low antimuscarinic activity; NO antimotion sickness actions
Drug interactions: MAOI prolong/intensify anticholinergic effects; additive sedative effects with sedatives; additive anticholinergic effects

Question 4

hydroxyzine

Answer 4

1st generation H1 antihistamine
MOA: reversibly bind to receptor and stabilize inactive form
Use: antiemetic (migraines), sedative, mild anxiolytic agent, skin allergies
Effects: sedation and antimuscarinic action
Drug interactions: MAOI prolong/intensify anticholinergic effects; additive sedative effects with sedatives; additive anticholinergic effects

Question 5

meclizine

Answer 5

1st generation H1 antihistamine
MOA: reversibly bind to receptor and stabilize inactive form
Use: motion sickness and vertigo
Effects: minimal antimuscarinic actions, less sedating than hydroxyzine
Drug interactions: MAOI prolong/intensify anticholinergic effects; additive sedative effects with sedatives; additive anticholinergic effects

Question 6

promethazine

Answer 6

1st generation H1 antihistamine
MOA: reversibly bind to receptor and stabilize inactive form
Use: antiemetic, antimotion sickness, antipsychotic, local anesthetic (block Na+ channels)
Effects: inhibit alpha 1 adrenergic receptor–> orthostatic hypotension; significant antimuscarinic effects
Drug interactions: MAOI prolong/intensify anticholinergic effects; additive sedative effects with sedatives; additive anticholinergic effects

Question 7

cyproheptadine

Answer 7

1st generation H1 antihistamine
MOA: reversibly bind to receptor and stabilize inactive form
Use: serotonin syndrome
Effects: low to moderate sedative and antimuscarinic activity; anti-serotonin activity–>increased appetite and weight gain
Drug interactions: MAOI prolong/intensify anticholinergic effects; additive sedative effects with sedatives; additive anticholinergic effects

Question 8

azelastine (Atelin)
fexofenadine (Allegra)
loratadine (Claritin)
desloratadine
(Clarinex)
cetirizine (Zyrtec)

Answer 8

2nd generation antihistamines (more selective than 1st gen.)
Less lipophilic
MOA: bind noncompetitively to H1 receptor
Use: treat allergic rhinitis, allergic conjunctivitis, uticaria
Effects: less sedation
Interaction: citrus juice and antacids can reduce bioavailability of fexofenadine

Question 9

cromolyn

nedocromil

Answer 9

Mast cell stabilizers
MOA: inhibition of Cl- channels in cell membrane–> inhibit degranulation
Use: allergic rhinitis, allergic conjunctivitis, antigen and exercise-induced asthma

Question 10

omalizumab

Answer 10

Recombinant humanized monoclonal antibody
MOA: bind IgE–> prevents binding to mast cells–> inhibit sensitization
Use: chronic urticaria, asthma
Expensive

Question 11

Doxepin

Answer 11

Tricyclic antidepressant
MOA: inhibits H1 and H2 receptors
Use: chronic urticaria

Question 12

ketotifen

Answer 12

H1 antihistamine and mast cell/basophil stabilizing properties
Use: allergic conjunctivitis
Ophthalmic prep.