antihistamines

Question 1

diphenhydramine (Benadryl)

Answer 1

Antihistamine
H1 (1G)
Tissues: peripheral H1 + CNS
main clinical use: allergies
main mode of action: blocks H1 receptors
adverse effects/note: drowsiness, (-) PS (dry mouth, blurred vision, etc). Good for motion sickness since H1 in CNS affects vestibular, vomiting

Question 2

dimenhydrinate (dramamine)

Answer 2

Antihistamine
H1 (1G)
Tissues: peripheral H1 + CNS
main clinical use: allergies
main mode of action: blocks H1 receptors
adverse effects/note: drowsiness, (-) PS (dry mouth, blurred vision, etc). Good for motion sickness since H1 in CNS affects vestibular, vomiting

Question 3

Chlorpheniramine (Chlor-Trimeton)

Answer 3

Antihistamine
H1 (1G)
Tissues: peripheral H1 + CNS
main clinical use: allergies
main mode of action: blocks H1 receptors
adverse effects/note: drowsiness, (-) PS (dry mouth, blurred vision, etc). Good for motion sickness since H1 in CNS affects vestibular, vomiting

Question 4

cyclizine (marezine)

Answer 4

Antihistamine
H1 (1G)
Tissues: peripheral H1 + CNS
main clinical use: allergies
main mode of action: blocks H1 receptors
adverse effects/note: drowsiness, (-) PS (dry mouth, blurred vision, etc). Good for motion sickness since H1 in CNS affects vestibular, vomiting

Question 5

meclizine (antivert, bonine)

Answer 5

Antihistamine
H1 (1G)
Tissues: peripheral H1 + CNS
main clinical use: allergies
main mode of action: blocks H1 receptors
adverse effects/note: drowsiness, (-) PS (dry mouth, blurred vision, etc). Good for motion sickness since H1 in CNS affects vestibular, vomiting

Question 6

promethazine (phenergan)

Answer 6

Antihistamine
H1 (1G)
Tissues: peripheral H1 + CNS
main clinical use: allergies
main mode of action: blocks H1 receptors
adverse effects/note: drowsiness, (-) PS (dry mouth, blurred vision, etc). Good for motion sickness since H1 in CNS affects vestibular, vomiting

Question 7

loratadine (claritin)

Answer 7

Antihistamine
H1 (2G)
Tissues: peripheral H1 only
main clinical use: allergies
main mode of action: blocks H1 receptors, but not those in CNS

Question 8

desloratadine (clarinex)

Answer 8

Antihistamine
H1 (2G)
Tissues: peripheral H1 only
main clinical use: allergies
main mode of action: blocks H1 receptors, but not those in CNS

Question 9

fexofenadine (allegra)

Answer 9

Antihistamine
H1 (2G)
Tissues: peripheral H1 only
main clinical use: allergies
main mode of action: blocks H1 receptors, but not those in CNS

Question 10

cetirizine (zyrtec)

Answer 10

Antihistamine
H1 (2G)
Tissues: peripheral H1 only
main clinical use: allergies
main mode of action: blocks H1 receptors, but not those in CNS

Question 11

cimetidine (Tagamet)

Answer 11

Antihistamine
H2
Tissues: stomach
main clinical use: antiacid
main mode of action: decreases gastric acid secretion

Question 12

ranitidine (zantac)

Answer 12

Antihistamine
H2
Tissues: stomach
main clinical use: antiacid
main mode of action: decreases gastric acid secretion

Question 13

famotidine (pepcid)

Answer 13

Antihistamine
H2
Tissues: stomach
main clinical use: antiacid
main mode of action: decreases gastric acid secretion

Question 14

H1(2G) - 5 drugs

Answer 14

acrivastine
loratidine (claritin)
desloratadine (clarinex)
fexofenadine (allegra)
cetirizine (zyrtec)

Question 15

H2 - 4 drugs

Answer 15

Cimetidine (tagamet)
ranitidine (zantac)
famotidine (pepcid)
nizatinide (axid)

Question 16

H1 (1G) - 6 main ones; 2 small

Answer 16

diphenhydramine (benadryl)
dimenhydrinate (dramamine)
chlorpheniramine (chlortrimeton)
cyclizine (marezine)
meclizine (antivert, bonine)
promethazine (phenergan)

clemastine (tavist)
tripelennamine

Question 17

general characteristics of 1st generation H1 antagonists

Answer 17

• muscarinic blocking effects! (drowsiness, dry mouth and airway, urinary retention)
• metbolized by hepatic cytochrome P450 (from 2nd generation - loratidine (claritin) is metabolized by CYP450)