GI Drugs Flashcards by Megan Haggerty

PPIs- PKs?

Omeprazole is a prodrug activated by stomach acid!

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PPIs- ADRs?

GI disturbance, headache, rash, osteoporosis

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PPIs- DDIs?

CYP inhibitor- increase MTX, decrease clopidogrel (reduced activation by CYP!)

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H2 antagonists- mechanism?

Antagonise H2 receptors -> decrease acid secretion, acts immediately and has short half life so take 2 x day

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H2 antagonists- ADRs?

GI disturbance, headache, gynaecomastia, hypotension

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H2 antagonists- DDIs?

Cimetidine is CYP inhibitor- increase AEDs, aminophylline, decrease clopidogrel

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PPIs- mechanism?

Inhibit H+/K+ ATPase (omeprazole IRREVERSIBLY inhibits!) -> decrease acid secretion! Takes days to have full effect (take out all pumps!)

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Domperidone- mechanism?

Dopamine (D2) antagonist -> inhibits vomiting response from trigger centre in 4th ventricle (postrema) ALSO increase rate of stomach emptying

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Domperidone- uses?

Acute N&V esp in parkinsons (caused by L-dopa)

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Ondansteron -mechanism?

Serotonin antagonist -> Inhibits postrema in 4th ventricle, inhibits vagal vomiting signals from GI tract

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Domperidone- ADRs?

Increased prolactin-> galactorrhoea, dystonia

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Ondansteron - uses?

Iatrogenic vomiting- chemotherapy and post op nausea

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Ondansteron- ADRs

Headache, constipation, flushing

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Hyoscine - mechanism?

ACh antagonist in vestibular apparatus -> stops MOTION SICKNESS

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Hyoscine ADRs

Anti-cholinergic effects plus bradycardia (unexpected!!)

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Cyclizine- mechanism?

Histamine (H1) antagonist -> inhibits vomiting centre in medulla and vestibular apparatus

Cyclizine- uses?

Acute N&V

Cyclizine- ADRs

Long QT, sedation

Metoclopramide- mechanism?

D2 antagonist, anti-cholinergic AND serotonin antagonist

Metoclopramide- uses?

GI causes of N&V, migraine, post op nausea

Metoclopramide- ADRs

Galactorrhoea, dystonia, extra pyramidal signs (avoid in parkinsons)

Drugs for hard faeces constipation?

Bulk forming, faecal softeners, osmotic laxatives

Soft faeces constipation?

Stimulant laxatives e.g. Senna

Bulk forming laxatives mechanism?

E.g isphaghula, indigestible vegetable fibre!! (Yum)

When don't use bulk laxatives?

Ulceration/adhesions -> obstruction!!

Faecal softeners- example, mechanism, uses?

E.g. Arachis oil, glycerol -> lubricate and soften stool, use in adhesions (no obstruction risk!), haemorrhoids and anal fissures

Osmotic laxatives- Mg/Na salts mechanism, example, uses?

E.g. Phosphate enema -> Increase water retention -> increase peristalsis, quick acting! Use in resistant constipation for urgent relief!!

Osmotic laxatives - lactulose mechanism, uses?

Galactose and fructose, bacteria FERMENT it -> acetic and latic acid -> osmotic effect, use in LIVER FAILURE (decreased ammonia)

Stimulant laxatives- example, mechanism?

Senna -> excite sensory nerves -> increase water and electrolyte retention -> increase peristalsis!

Stimulant laxatives- ADRs and contra indications

Abdo cramps, colonic atony, hypokalaemia DONT use in OBSTRUCTION

Anti motility drugs- example, mechanism?

Loperamide (opiate analogue) -> opioid receptors in bowel -> decrease motility, increase time for water and salt resorption, increase anal tone, decrease defecation reflex

Loperamide- indications and contraindications

Use in chronic diarrhoea NOT in IBD as -> toxic megacolon

Anti-spasmodics- example, mechanism, uses?

Meberavine, anti-muscarinic-> decrease spasms and painful cramps, maintain motility, use with bulk forming agent to treat IBS!