Histamine & Serotonin Flashcards
What is an H1 antagonist used for?
Allergic reactions, motion sickness, nausea and vomiting in pregnancy, sleep aids
What are common side effects of H1 antagonists?
Sedation, anti-muscarinic action, poisoning (especially children) with convulsions, allergy, local anesthesia
Older agents cross CNS to cause central effects
Where are H1 antagonists metabolized? What are the oral absorption and distribution properties?
rapid metabolism by liver microsomes
Rapidly absorbed orally and widely distributed
What is the mechanism of action of these drugs?
Tripelennamine (Pyribenzamine)
Meclizine (Dramamine II, Antivert)
Hydroxyzine (Atarax)
Promethazine (Phenergan)
Chlorpheniramine (Chlor-Trimeton)
Diphenhydramine (Benadryl)
H1 receptor antagonists
what is a common OTC sleep aid?
Tripelennamine (Pyribenzamine)
Ethylenediamine derivitive
H1 receptor antagonist
What histamine blockers are used for motion sickness?
Meclizine (Dramamine II, Antivert)
Hydroxyzine (Atarax)
Piperazine derivative
H1 receptor antagonist
What is a major side effect of diphenhydramine?
Anti-muscarinic, sedating
Ether/ethanolamine derivitive
H1 receptor antagonist
What is promethazine used for?
Antiemetic
Phenothiazine derivative
H1 receptor antagonist
Anti-muscarinic, sedating
what is chlorpheniramine?
Alkylamine derivitive
H1 receptor antagonist
Component of “cold” medications
Less sedating
What is the mechanism of action? What are they used to treat?
Loratadine
Fexofenadine
Azelastine
Cetirizine
2nd generation H1 receptor antagonists
2nd gen H1 blockers treat allergic rhinitis
Loratadine (Claritin)
Fexofenadine (Allegra)
Azelastine (Astelin)
Cetirizine (Zyrtec)
What is major difference between 1st and second gen H1 blockers?
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)
What is azelastine?
2nd generation H1 receptor antagonist
Treats allergic rhinitis (intranasal spray), allergic conjunctivitis (ophthalmic solution)
What antihistamines can cause cardiovascular effects at high doses?
Loratadine (Claritin)
Fexofenadine (Allegra)
2nd generation H1 receptor antagonist
What is the mechanism of action? What are the “…tidine” drugs used for?
Cimetidine
Ranitidine
Famotidine
Nizatidine
H2 receptor antagonists; block gastric acid secretion (more so with nocturnal acid secretion than meal secretion)
What class of drugs are used to treat dyspepsia, duodenal and gastric ulcers, hypersecretory conditions? What is a common possible side effect?
H2 receptor antagonists; block gastric acid secretion (more so with nocturnal acid secretion than meal secretion)
CNS dysfunction
Of the H2 receptor antagonists, which has the most side effects? What are they?
Cimetidine (Tagamet)
Antiandrogen effects (causing impotence and gynecomastia), inhibition of P450 enzymes
What is Rantidine? What is the most concerning side effect?
Zantac - H2 receptor antagonist; blocks gastric acid secretion (more so with nocturnal acid secretion than meal secretion)
liver toxicity
CNS dysfunction possible
Of the H2 antagonists, which has the least side effects?
Nizatidine (Axid)
What is ketanserin? what is it used for?
Selective 5HT2A,2C receptor antagonist, as well as α1 and H1 receptor antagonist
Antihypertensive (relaxes vascular and tracheal smooth muscle), antiplatelet aggregation
Mechanism of action for the “…setron” drugs? Used for?
Odansetron
Granisetron
5HT3 receptor antagonists
Nausea and vomiting in chemotherapy
“…SErotoninThreeReceptor antagonist used by ONcologists”
5-HT = serotonin
What is Cyproheptadine?
Dual action antihistaminic and antiserotinergic
used for skin allergies (urticaria, anti-5HT1), diarrhea of carcinoid syndrome (anti-5HT2)
Side effects: Sedation, antimuscarinic
What class of drugs? What is a common side effect?
Methysergide
Ergonovine
Bromocriptine
Ergotamine
Ergot alkaloid
Powerful hallucinations, smooth muscle contraction (vascular and uterine)
Which ergot alkaloid is used to treat hyperprolactinemia? Why?
Bromocriptine (Sansert)
because it’s a dopamine agonist - DA inhibits prolactin release from anterior pituitary
What does ergonovine treat?
Postpartum hemorrhage (Oxytocic)
What is methysergide? What is it used for?
ergot alkaloid
Partial agonist at all 5HT1 receptors, antagonist at 5HT2
Prophylaxis of migraines
What is ergotomine? What is it used for?
Ergot alkaloid
Nonspecific partial agonist at all 5HT1,2 receptors; partial agonist at α-adrenergic receptors
Prodrome of migraines
What are triptans? Mechanism? Used for?
Sumatriptan
Naratriptan
Rizatriptan
Zolmitriptan
Non-ergot serotonin analogs
5HT1B,D receptor agonist
Effective (70%) migraine treatment
Why should you analyze doses of other drugs and consider lowering them in a patient who is taking cimetidine?
Cimetidine has an effect on the cytochrome P450 system.
H1 receptors are found mainly:
skin, lungs, GI, nasal mucosa and blood
What drugs induce histamine release?
Morphine
Codeine
ACh
tubocurarine
H1 receptors are found:
smooth muscle, endothelium brain (hence drowsiness - CNS effect of H1 antagonism)
H2 receptors are found:
gastric mucosa (think H-blockers for acid reflux), cardiac muscle, mast cells, brain
H3 receptors are found:
CNS
H4 receptors are found:
eosinophils
neutrophils
CD4+ T cells
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
H1 receptor antagonists
Antihistamines
H1 receptor antagonists are largely ineffective for what conditions?
Bronchial asthma
colds
How is Nizatidine different from other H2 receptor antagonists?
It does not affect the cytochrome P450 system
Liver toxicity is a side effect of what H2 receptor blocker?
Ranitidine
Gynecomastia and impotence are side effects of what H2 receptor blocker?
Cimetidine
How are loradidine and fexofenadine different from other H1 receptor blockers?
They cross the BBB poorly, so less sedating;
fewer side effects in general
What is 5-hydroxytryptamine?
Serotonin
Release of 5-HT can be induced by what drug?
Reserpine
