Unit 2. Histamine & Serotonin

Question 1

Diphenhydramine

Answer 1

Class: H1 blockers (1st gen)
MOA: antag @ H1
Uses: allergic rxns (not bronchial asthma, colds), motion sickness, N/V of pregnancy, “sleep aids”
Tox: sedation, atropine/anti-musc effects; can lead to poisoning (children), convulsions, allergy, local anesthesia
Note: 1st gen cross BBB, so get central effects

Question 2

Tripelennamine

Answer 2

Class: H1 blockers (1st gen)
MOA: antag @ H1
Uses: OTC "sleep aids"
Tox: moderately sedating
Note: 1st gen cross BBB, so get central effects

Question 3

Cyclazine

Answer 3

Class: H1 blockers (1st gen)
MOA: antag @ H1
Uses: anti-motion sickness (but others better)
Tox: sedation
Note: 1st gen cross BBB, so get central effects

Question 4

Promethazine

Answer 4

Class: H1 blockers (1st gen)
MOA: antag @ H1
Uses: anti-emetic
Tox: marked sedation & anti-musc effects
Note: 1st gen cross BBB, so get central effects

Question 5

Chlorpheniramine

Answer 5

Class: H1 blockers (1st gen)
MOA: antag @ H1
Uses: component of cold meds
Tox: less sedating ("day time")
Note: 1st gen cross BBB-->central effects; cheap

Question 6

Loratidine

Answer 6

Class: H1 blockers (2nd gen)
MOA: antag @ H1
Uses: allergic rhinitis
Tox: CV effects (Vtach) rare, @high doses
Note: 2nd gen, does not cross BBB; so NO sedation, central effects; longer t1/2 so QD dosing; more expensive

Question 7

Fexofenadine

Answer 7

Class: H1 blockers (2nd gen)
MOA: antag @ H1
Uses: allergic rhinitis
Tox: CV effects (Vtach) rare, @high doses
Note: 2nd gen, does not cross BBB; so NO sedation, central effects; longer t1/2 so QD dosing; more expensive

Question 8

Azelastine

Answer 8

Class: H1 blockers (2nd gen)
MOA: antag @ H1
Uses: allergic rhinitis (intranasal spray), allergic conjunctivitis (opthalm soln)
Note: no sedation, central effects (2nd gen)

Question 9

Cetirizine

Answer 9

Class: H1 blockers (2nd gen)
MOA: antag @ H1
Uses: allergic rhinitis (zyrtec); used in combo w decongestant
Note: no sedation, central effects (2nd gen)

Question 10

Cimetidine

Answer 10

Class: H2 blockers
MOA: antag @ H2–> blocks gastric acid secretion (moreso nocturnal than at meals)
Uses: dyspepsia, duod+gastric ulcers, hypersecretory conditions (e.g. Zollinger-Ellison syndrome)
Tox: anti-androgen (impotence, gynecomastia), inhib of p450s (drug rxns!), CNS dysfxn in elderly

Question 11

Ranitidine

Answer 11

Class: H2 blockers
MOA: antag @ H2–> blocks gastric acid secretion (moreso nocturnal than at meals)
Uses: dyspepsia, duod+gastric ulcers, hypersecretory conditions (e.g. Zollinger-Ellison syndrome)
Tox: liver toxicity, CNS dysfxn in elderly

Question 12

Famotidine

Answer 12

Class: H2 blockers
MOA: antag @ H2–> blocks gastric acid secretion (moreso nocturnal than at meals)
Uses: dyspepsia, duod+gastric ulcers, hypersecretory conditions (e.g. Zollinger-Ellison syndrome)
Tox: CNS dysfxn possible in elderly

Question 13

Nizatidine

Answer 13

Class: H2 blockers
MOA: antag @ H2–> blocks gastric acid secretion (moreso nocturnal than at meals)
Uses: dyspepsia, duod+gastric ulcers, hypersecretory conditions (e.g. Zollinger-Ellison syndrome)
Tox: least side effects of H2 blockers (drug of choice)

Question 14

Cyproheptadine

Answer 14

Class: 5HT blockers
MOA: antiserotinergic and antihistaminic
Uses: skin allergies/urticaria (anti-H1), diarrhea of carcinoid syndrome (anti-5HT2)
Tox: sedation, antimusc effects

Question 15

Ketanserin

Answer 15

Class: 5HT blockers
MOA: selective antag @ 5HT2A,2C; also antag @ alpha1, H1
Uses: antiHTN (relaxes vasc and tracheal smooth muscle), anti-platelet aggregation

Question 16

Ondansetron

Answer 16

Class: 5HT blockers
MOA: antag @ 5HT3 (*only ion channel rec)
Uses: prevention of N/V assoc w chemo

Question 17

Ergotamine

Answer 17

Class: Ergot alkaloids
MOA: nonspecific partial agonist @ all 5-HT1, 2 receptors; agonist/antag @ alpha receptors
Uses: prodrome of migraines
Tox: N/V, cumulative+prolonged vasoconstriction
Note: combine w caffeine–>CAFERGOT

Question 18

Methylsergide

Answer 18

Class: Ergot alkaloids
MOA: partial agonist @ all 5-HT1 rec; antag @ 5HT2
Uses: migraine prophylaxis
Tox: GI disturbances, inflammatory fibrosis (chronic use), hallucinations **withdrawn

Question 19

Ergonovine

Answer 19

Class: Ergot alkaloid
MOA: alpha agonist
Use: postpartum hemorrhage (oxytocic)

Question 20

Bromocriptine

Answer 20

Class: Ergot alkaloid
MOA: agonist @ D2–>suppresses prolactin release from pituitary cells
Uses: prolactinemia, parkinsonism

Question 21

Triptans

Answer 21

Class: Non-ergot 5HT analogs
MOA: agonists @ 5HT1B, 1D –> vasoconstriction and pre-synaptic inhibition of release of pro-inflam peptides
Uses: effective (70%) migraine treatment

Question 22

Name the 1st ten H1 blockers; what does 1st gen imply?

Answer 22

Diphenhydramine, Tripelennamine, cyclizine, promethazine, chlorpheniramine

1st gen crosses BBB–> sedation + central effects

Question 23

Name the 2nd gen H1 blockers

Answer 23

Loratidine, Fexofenadine, Azelastine, Cetirizine

Question 24

Name the H2 blockers; which is drug of choice?

Answer 24

Cimetidine, Ranitidine, Famotidine, Nizatidine
-Nizatidine is choice drug because has least side effects (does not inhibit p450s, no hepatotox, no anti-androgen effects)

Question 25

Name the serotonin blockers; which receptors do they antagonize?

Answer 25

Cyproheptadine, Ketanserin, Ondansetron

1. 5HT2, H1 (plus other 5HTs likely)
2. 5HT 2A, 2C; also alpha1, H1
3. 5HT3

Question 26

Name the ergot alkaloids; which drug class is better than ergots for migraines?

Answer 26

Ergotamine, Methylsergide, Ergonovine, Bromocriptine

-Triptans better for migraines; can use ergotamine in prodrome