Pharm Chem Exam 1 Part 4

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  1. Histamine
    histamine is synthesized from the essential AA histidine through histidine decarboxylase
  2. Histamine (HA) receptor subtypes
    H1: mast cells store histamine in granules as heparin salts (sulfate)

    H2: enterochromafffin-like cells of gastric mucosa; activate protein pump which secretes HCl
  3. First generation antihistamines: H1-receptor antagonists
    see pharmacophore on page 33
  4. Diphenhydramine (NyQuil, Robitussin)
    • 1G antihistamine: H1 receptor antagonist
    • X=O
    • enthanolamine antihistamine
    • salt version: Benadryl (diphenhydramine chlorotheophyllinate) decreases drowsiness due to the stimulant effect of theophylline
    • chloro group of benadryl increases acidity salt and favors the salt conformation
  5. Pyrilamine (Midol)
    • 1G H1-receptor antagonists
    • X=N
    • ethylenediamine antihistamine
    • less anticholinergic SEs which can induce cough
  6. Chlorpheniramine
    • 1G H1-receptor antagonists
    • X=C
    • alkylamine antihistamine
    • reduced drowsiness
    • FYI: other examples: dimetapp, acetifed
  7. Hydroxyzine (Vistaril)
    • 1G H1-receptor antagonists
    • piperazine antihistamine
  8. Promethazine (Phenergan)
    • 1G H1-receptor antagonists
    • phenothiazine antihistamine
    • 10% as antidopaminergic as chlorpromazine
    • Tx: allegic rhinitis, N&V, muscarinic antagonist
  9. 2G H1-receptor antagonists
    • non-sedating
    • highly polar preventing penetration of BBB
  10. Terfenadine (Seldane)
    • 2G H1-receptor antagonists
    • victim drug
    • oxidized by 3A4 (DDIs!!!!!)
    • perpertrator drug
  11. Fexofenadine (Allegra)
    • 2G H1-receptor antagonists
    • %F unknown
    • fecal elimination
    • good Pgp substrate
    • no known DDIs
  12. Loratadine (Claritin)
    • 2G H1-receptor antagonist
    • shorter half life than parent drug desloratadine
    • metabolized by 2D6 and 3A4 DDIs: carbamate --- amine
    • went from Rx to OTC
  13. Desloratadine (Clarinex)
    • 2G H1-receptor antagonist
    • long half life
    • no 3A4 DDI or 2D6 polymorphism
    • premetabolized
    • BBB Pgp effluxes BBB --- non-sedative
  14. Cetirizine (Zyrtec)
    • 2G H1 receptor antagonist
    • metabolite of 1G hydroxyzine
    • COOH derivative so it does not cross BBB so much is excreted unchanged (typical of AA drugs) --- also decreases DDI
  15. Levocetirizine
    • racemic switch of cetirizine
    • claims of decreased sedation
  16. H2 receptor antagonists (blockers)
    Tx: gastric ulcers, GERD
  17. Cimitidine (Tagament)
    • H2 receptor antagonist
    • largely excreted unchanged
    • guanidine-like functional group
    • imidazole problem
    • binds to and inhibits a wide range of CYPs --- many DDIs
    • inhibits gastric alcohol dehydrogenase
  18. Ranitadine
    • H2 receptor antagonist
    • largely excreted unchanged
    • no imidazole ring --- only 10% as much CYP inhibition as cimitidine
    • "me better" drug of cimitidine
  19. Famotidine (Pepcid)
    • H2 receptor antagonist
    • no CYP inhibition
    • "me too" drug of cimitidine
  20. Nizatidine (Axid)
    • H2 receptor antagonist
    • 90% bioavailable
    • no CYP inhibition
    • "me too" drug of cimitidine
  21. Proton Pump Inhibitors (PPIs)
    • covalent binding to sulfhydryl group on parietal cells
    • targets proton and/or potassium pumps
  22. Omeprazole (Prilosec)
    • PPI
    • broad range of PD half life because it is a prototypic 2C19 inhibitor
    • 3A4 substrate
    • marketed as a racemic sulfoxide
    • enteric coated to prevent premature activation
  23. Tx: GERD
    PPI + amoxicillin + clarithromycin (H. Pylori)
  24. Esomeprazole (Nexium)
    • PPI
    • S-enantiomer eliminating 2C19 issues leading to predicatable plasma levels of parent drug and clarithromycin
    • dose: 2x of omeprazole
    • chiral center is at the S-sulfoxide group
  25. Lansoprazole (Prevacid)
  26. Pantoprazole (Protonix)
    • PPI
    • more acid stable so not affected by food stimulated acid production
  27. Rabeprazole (Aciphex)
    • PPI
    • sulfone group is acted on by 3A4 and the O-demethyl group is acted on by 2C19
  28. PPI PD:
    • irreversible long acting inhibitors of H+, K+ ATPase
    • forms cystine (disulfide) linkages with enzyme after prodrug is acid-activated to electrophilic sulfenamide
    • ion trapping effect at canaliculi
  29. Misoprostol (Cytotec)
    • Prostaglandin
    • Tx: anticulcer, NSAID-induced ulcers
    • opposes influence of HA on PP
  30. THC
    • marijuana
    • makes your hair grow --- Hippies!
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Pharm Chem Exam 1 Part 4
2012-01-27 22:04:44
Pharm Chem Exam Part

Pharm Chem Exam 1 Part 4
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