Histamine & Serotonin

Question 1

What is an H1 antagonist used for?

Answer 1

Allergic reactions, motion sickness, nausea and vomiting in pregnancy, sleep aids

Question 2

What are common side effects of H1 antagonists?

Answer 2

Sedation, anti-muscarinic action, poisoning (especially children) with convulsions, allergy, local anesthesia

Older agents cross CNS to cause central effects

Question 3

Where are H1 antagonists metabolized? What are the oral absorption and distribution properties?

Answer 3

rapid metabolism by liver microsomes

Rapidly absorbed orally and widely distributed

Question 4

What is the mechanism of action of these drugs?

Tripelennamine (Pyribenzamine)

Meclizine (Dramamine II, Antivert)

Hydroxyzine (Atarax)

Promethazine (Phenergan)

Chlorpheniramine (Chlor-Trimeton)

Diphenhydramine (Benadryl)

Answer 4

H1 receptor antagonists

Question 5

what is a common OTC sleep aid?

Answer 5

Tripelennamine (Pyribenzamine)

Ethylenediamine derivitive

H1 receptor antagonist

Question 6

What histamine blockers are used for motion sickness?

Answer 6

Meclizine (Dramamine II, Antivert)

Hydroxyzine (Atarax)

Piperazine derivative

H1 receptor antagonist

Question 7

What is a major side effect of diphenhydramine?

Answer 7

Anti-muscarinic, sedating

Ether/ethanolamine derivitive

H1 receptor antagonist

Question 8

What is promethazine used for?

Answer 8

Antiemetic

Phenothiazine derivative

H1 receptor antagonist

Anti-muscarinic, sedating

Question 9

what is chlorpheniramine?

Answer 9

Alkylamine derivitive

H1 receptor antagonist

Component of “cold” medications

Less sedating

Question 10

What is the mechanism of action? What are they used to treat?

Loratadine
Fexofenadine
Azelastine
Cetirizine

Answer 10

2nd generation H1 receptor antagonists

2nd gen H1 blockers treat allergic rhinitis

Loratadine (Claritin)
Fexofenadine (Allegra)
Azelastine (Astelin)
Cetirizine (Zyrtec)

Question 11

What is major difference between 1st and second gen H1 blockers?

Answer 11

second gen blockers poorly cross BBB, so fewer central and side effects - e.g. no sedation, although rare cadiovascular effects at high doses in loratadine (claratin) and fexofenadine (allegra)

Question 12

What is azelastine?

Answer 12

2nd generation H1 receptor antagonist

Treats allergic rhinitis (intranasal spray), allergic conjunctivitis (ophthalmic solution)

Question 13

What antihistamines can cause cardiovascular effects at high doses?

Answer 13

Loratadine (Claritin)
Fexofenadine (Allegra)

2nd generation H1 receptor antagonist

Question 14

What is the mechanism of action? What are the “…tidine” drugs used for?

Cimetidine
Ranitidine
Famotidine
Nizatidine

Answer 14

H2 receptor antagonists; block gastric acid secretion (more so with nocturnal acid secretion than meal secretion)

Question 15

What class of drugs are used to treat dyspepsia, duodenal and gastric ulcers, hypersecretory conditions? What is a common possible side effect?

Answer 15

H2 receptor antagonists; block gastric acid secretion (more so with nocturnal acid secretion than meal secretion)

CNS dysfunction

Question 16

Of the H2 receptor antagonists, which has the most side effects? What are they?

Answer 16

Cimetidine (Tagamet)

Antiandrogen effects (causing impotence and gynecomastia), inhibition of P450 enzymes

Question 17

What is Rantidine? What is the most concerning side effect?

Answer 17

Zantac - H2 receptor antagonist; blocks gastric acid secretion (more so with nocturnal acid secretion than meal secretion)

liver toxicity

CNS dysfunction possible

Question 18

Of the H2 antagonists, which has the least side effects?

Answer 18

Nizatidine (Axid)

Question 19

What is ketanserin? what is it used for?

Answer 19

Selective 5HT2A,2C receptor antagonist, as well as α1 and H1 receptor antagonist

Antihypertensive (relaxes vascular and tracheal smooth muscle), antiplatelet aggregation

Question 20

Mechanism of action for the “…setron” drugs? Used for?

Odansetron
Granisetron

Answer 20

5HT3 receptor antagonists

Nausea and vomiting in chemotherapy

“…SErotoninThreeReceptor antagonist used by ONcologists”

5-HT = serotonin

Question 21

What is Cyproheptadine?

Answer 21

Dual action antihistaminic and antiserotinergic

used for skin allergies (urticaria, anti-5HT1), diarrhea of carcinoid syndrome (anti-5HT2)

Side effects: Sedation, antimuscarinic

Question 22

What class of drugs? What is a common side effect?

Methysergide
Ergonovine
Bromocriptine
Ergotamine

Answer 22

Ergot alkaloid

Powerful hallucinations, smooth muscle contraction (vascular and uterine)

Question 23

Which ergot alkaloid is used to treat hyperprolactinemia? Why?

Answer 23

Bromocriptine (Sansert)

because it’s a dopamine agonist - DA inhibits prolactin release from anterior pituitary

Question 24

What does ergonovine treat?

Answer 24

Postpartum hemorrhage (Oxytocic)

Question 25

What is methysergide? What is it used for?

Answer 25

ergot alkaloid Partial agonist at all 5HT1 receptors, antagonist at 5HT2 Prophylaxis of migraines

Question 26

What is ergotomine? What is it used for?

Answer 26

Ergot alkaloid Nonspecific partial agonist at all 5HT1,2 receptors; partial agonist at α-adrenergic receptors Prodrome of migraines

Question 27

What are triptans? Mechanism? Used for? Sumatriptan Naratriptan Rizatriptan Zolmitriptan

Answer 27

Non-ergot serotonin analogs 5HT1B,D receptor agonist Effective (70%) migraine treatment

Question 28

Why should you analyze doses of other drugs and consider lowering them in a patient who is taking cimetidine?

Answer 28

Cimetidine has an effect on the cytochrome P450 system.

Question 29

H1 receptors are found mainly:

Answer 29

skin, lungs, GI, nasal mucosa and blood

Question 30

What drugs induce histamine release?

Answer 30

Morphine Codeine ACh tubocurarine

Question 31

H1 receptors are found:

Answer 31

smooth muscle, endothelium brain (hence drowsiness - CNS effect of H1 antagonism)

Question 32

H2 receptors are found:

Answer 32

gastric mucosa (think H-blockers for acid reflux), cardiac muscle, mast cells, brain

Question 33

H3 receptors are found:

Answer 33

CNS

Question 34

H4 receptors are found:

Answer 34

eosinophils neutrophils CD4+ T cells

Question 35

``` These classes of drugs are all what kind of drug? Ethers or ethanolamine derivatives Ethylenediamine derivative Piperazine derivative Phenothiazine derivative Alkylamine derivative Piperidine derivative Azelastine ```

Answer 35

H1 receptor antagonists | Antihistamines

Question 36

H1 receptor antagonists are largely ineffective for what conditions?

Answer 36

Bronchial asthma | colds

Question 37

How is Nizatidine different from other H2 receptor antagonists?

Answer 37

It does not affect the cytochrome P450 system

Question 38

Liver toxicity is a side effect of what H2 receptor blocker?

Answer 38

Ranitidine

Question 39

Gynecomastia and impotence are side effects of what H2 receptor blocker?

Answer 39

Cimetidine

Question 40

How are loradidine and fexofenadine different from other H1 receptor blockers?

Answer 40

They cross the BBB poorly, so less sedating; | fewer side effects in general

Question 41

What is 5-hydroxytryptamine?

Answer 41

Serotonin

Question 42

Release of 5-HT can be induced by what drug?

Answer 42

Reserpine