How are H1 receptor antagonists metabolized and how fast?
rapidly metabolized via liver microsomes
What are H1 receptor antagonists used for and what are their general side effects?
Use: allergic reactions, motion sickness, nausea and vomiting in pregnancy, sleep aids.
SE: sedation; anti-muscarinic action, poisoning (especially children) with convulsions, allergy, local anesthesia
Diphenhydramine (Benadryl)
class
mech
SE
Ether/ethanolamine derivative
H1 receptor antagonist
SE: anti-muscarinic, sedation
Tripelennamine
Class
Mech
Use
ethylenediamine derivative
H1 receptor antagonist
Use: OTC sleep aid
Cyclizine
Class
Mech
Use
Piperazine derivative
H1 receptor antagonist
Use: Motion sickness
Promethazine class mech use SE
phenothiazine derivative
H1 receptor antagonist
Use: Antiemetic
SE: Anti-muscarinic, sedation
Chlorpheniramine Class mech use SE
Alkylamine
H1 receptor antagonist
Use: Component of cold meds
SE: less sedation
Laratadine (claritin) class mech use SE
Piperidine derivative
2nd gen H1 receptor antagonist
Use: Allergic rhinitis
SE: no sedation, rare CV effects
Fexofenadine (allegra) Class mech use SE
Piperidine derivative
2nd gen H1 receptor antagonist
Use: Allergic rhinitis
SE: no sedation, rare CV effects
Azelastine
mech
use
SE
2nd gen H1 receptor antagonist
Use: allergic rhinitis (internasal spray), allergic conjunctivitis (opthalmic solution)
SE: No sedation
Cetirizine
mech
use
SE
2nd gen H1 receptor antagonist
Use: allergic rhinitis
SE: No sedation
Cimetidine
Mech
use
SE
H2 receptor antagonist; blocks gastric acid secretion (more so with nocturnal acid secretion than meal secretion)
Use: Dyspepsia, duodenal and gastric ulcers, hypersecretory conditions
SE: Antiandrogen (causing impotence and gynecomastia), inhibition of P450 enzymes
Ranitidine (Zantac)
Mech
Use
SE
H2 receptor antagonist; blocks gastric acid secretion (more so with nocturnal acid secretion than meal secretion)
Use: Dyspepsia, duodenal and gastric ulcers, hypersecretory conditions
SE: Liver toxicity
Famotidine
Mech
Use
H2 receptor antagonist; blocks gastric acid secretion (more so with nocturnal acid secretion than meal secretion)
Use: Dyspepsia, duodenal and gastric ulcers, hypersecretory conditions
Nizatidine
Mech
Use
H2 receptor antagonist; blocks gastric acid secretion (more so with nocturnal acid secretion than meal secretion)
Use: Dyspepsia, duodenal and gastric ulcers, hypersecretory conditions
Why do second gen H1 antagonists cause less sedation?
poorly cross BBB
What is a possible SE of all H2 antagonists?
CNS dysfunction possible
Cyproheptadine
mech
Use
SE
Antihistaminic and antiserotinergic
Use: Skin allergies (urticaria, anti-5HT1)
Diarrhea of carcinoid syndrome (anti 5HT2)
SE: Sedation, antimuscarinic
Ketanserin
Mech
Use
Selective 5HT2A, 2C receptor antagonist as well as alpha 1 and H1 receptor antagonist
Use: Antihypertensive (Relaxes vascular and tracheal smooth muscle), antiplatelet aggregation
Odansetron
Mech
Use
5HT3 receptor antagonist
Use: Nausea and vomiting in chemotherapy
Ergot Alkaloids
Mech
SE
Agonist and antagonist actions at 5HT and alpha adrenergic receptors (also some dopamine)
SE: powerful hallucinations, smooth muscle contraction (vascular and uterine)
Ergotamine Class Mech Use SE
Ergot alkaloid
nonspecific partial agonist at all 5HT1,2 receptors; partial agonist at alpha adrenergic receptors
Use: Prodrome of migraines
SE: N/V, cumulative and prolonged vasoconstriction
Methysergide Class Mech use SE
Ergot alkaloid
partial agonist at all 5HT1 receptors, antagonist at 5HT2
Use: Prophylaxis of migraines
SE: GI disturbances, inflammatory fibrosis (chronic use), hallucinations
Ergonovine
Class
Mech
Use
ergot alkaloid
alpha agonists
pospartum hemorrhage (Oxytocic)
Bromocriptine
Class
Mech
Use
Ergot alkaloid
Dopamine agonist
Use: parkinsonism, hyperprolactinemia
Triptans
Class
Mech
Use
Non-ergot serotonin analog
5HT1,b,D receptor agonist
Use: Effective (70%) migraine treatment.