P year‎ > ‎Pharmacology‎ > ‎

13.02.07 GI pharmacology

Clopidogrel + PPI Interaction
  • PPIs reduce the effectiveness of clopidogrel in preventing the recurrence of adverse cardiac events such as heart attack and coronary artery restenosis


Drugs increasing mucosal resistance

  • Physical barriers
    • Bismuth
    • Sucralfate
  • Prostaglandin analogues
    • Misoprostol


Antacids

  • Increase rate of emptying => Short effect
  • Stimulate gastrin release => Tolerance/adaptation


H. pylori eradication

  • Must have a PPI
  • Plus any two of:
    • Amoxicillin
    • Metronidazole
    • Clarythromycin
  • Doses vary depending on combination
  • Choose the ones patient hasn't taken recently


Management of constipation

  • Contraindications
    • Intestinal perforation or obstruction
  • Bulk-forming
    • Fybogel, Methylcellulose
  • Stimulants (NB abdo. cramps)
    • Anthraquinones
      • Senna
      • Co-danthramer (palliative only - ?carcinogenic)
    • Docusate sodium (dual effect)
    • Diphenylmethabe derivatives
  • Softeners (NB risk of incontinence)
    • Docusate sodium
    • Liquid parafin
  • Osmotic
    • Lactulose
    • PEG (Movicol)
    • Magnesium salts
    • Phosphate


Diarrhoea

  • Drug causes
    • Magnesium-containing antacids
    • NSAIDs
    • Lithium
    • PPIs
  • Treatment
    • Rehydration fluids MUST CONTAIN GLUCOSE for salt uptake
    • Generally no Abx
  • C. diff
    • Treat with oral metronidazole or vancomycin
  • Antimotility drugs
    • NEVER in anyone <12


Nausea + vomiting pathways

  • Chemoreceptor trigger zone
    • Dopamine + 5-HT3 serotonin receptor
  • Vestibular
    • Cholinergic muscarinic receptor 
  • Vomiting centre pathways
    • Histamine + cholinergic muscarinic receptors
  • Gastric status
    • Dopamine + 5-HT4 serotonin receptor


Antiemetics

  • Metoclopramide
    • Dopamine D2 antagnoist
    • => Causes dystonia, esp. if <18 or >70
      • Can treat with procyclidine (anticholinergic)
  • Promethazine
    • 1st generation antihistamine
    • Safe in pregnancy (e.g. hyperemesis gravidarum)
    • Sedative effects

Crohn's remission
  • Yes
    • Azathioprine
    • Infliximab
    • Methotrexate
  • No
    • Aminosalicilates (but probably not harmful so often continued)
    • Cyclosporin (high risk of adverse events)
    • Corticosteroids (harm > benefit)

Stomach acid secretion



Notes
  • Metronidazole tastes bad
  • Beware antimotility drugs in UC
    • => Paralytic ileus + megacolon
Comments