GI Flashcards by joe rose-grey

What drug class is Gaviscon?

antacid and alginate

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How do antacids work?

they buffer the stomach acid to raise the pH of the stomach contents

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how do alginates work?

increase the viscosity of stomach contents and form a floating raft to form a barrier between the gastric contents and the GOJ

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what are the indications to take Gaviscon (antacids/alginates)?

GORD

2. dyspepsia

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what are the contra-indications to taking Gaviscon (antacids/alginates)?

Frequent alcohol use, severe dehydration, renal impairment

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what are the side effects to Gaviscon?

normally well tolerated

can cause: Nausea, constipation, diarrhoea (from magnesium), headache

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what are possible interactions of alginates?

they bind to other drugs and can reduce absorption

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what are the possible interactions of antacids?

can reduce serum concentrations of other drugs e.g. ACEi, some abx, PPIs etc
increase excretion of aspirin and lithium

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What class of drug is Ranitidine?

H2 antagonist

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How do H2 antagonists work?

Reduce gastric acid output by blocking histamine H2-receptors

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what are the indications for taking Ranitidine?

Peptic ulcer disease -gastric and duodenal ulcers (including NSAID related ulcers)
GORD

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what are the contra-indications for taking Ranitidine?

hepatic and renal impairment (metabolised by liver and excreted by kidneys)

can disguise symptoms of gastric cancer

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what are the side-effects of Ranitidine?

Diarrhoea, headache, dizziness

rarely: hepatitis, cholestatic jaundice, bradycardia

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what are the possible interactions of Ranitidine?

increases plasma conc and side effects of Loperamide

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how quickly is Ranitidine eliminated from the body?

Half-life: 2.5 hours (oral with normal renal function)

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Why take H2 antagonists over PPIs?

although H2 antagonists are just shit PPIs (less complete acid suppression) they have a quicker onset. this can be useful pre-operation especially.

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What class of drug are Lansoprazole and Omeprazole?

PPIs

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How do PPIs work?

they reduce gastric acid secretion by irreversibly inhibiting H+/K+ ATPase in gastric parietal cells. aka the proton pump bringing in H+

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what are the indications to take PPIs?

Peptic ulcer/NSAID ulcers
dyspepsia/ GORD
eradication of H. Pylori (in combo with abx)

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what are the conta-indications to taking PPIs?

disguise symptoms of gastric cancer
increase risk of fracture (warning in osteoporosis)

(hepatic impairment, interstitial nephritis, C diff colitis)

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what are the side effects to PPIs?

GI disturbance (nausea, vomiting, abdo pain, flatulence, diarrhoea, constipation), headache

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what are the possible interactions with PPIs?

P450 enzyme inhibitor

reduce effect of clopidogrel
Diazepam, warfarin and phenytoin (prolongs elimination)
citalopram; atazanavir; dasatinib; tenofovir; methotrexate (increase blood levels and effects)

How are PPIs eliminated?

Eliminated mainly in urine as broken down metabolites

What class of drug is Loperamide?

Antimotility drug - anti-diarrhoeal agent

How does Loperamide work?

agonist of opiod receptors in GI tract - decreases peristaltic movements - increases anal tone allows more water to be absorbed from stool as longer in the bowel

what are the indications to take Loperamide?

diarrhoea

what are the contra-indications to taking Loperamide?

avoid in UC - greater chance of toxic megacolon C. diff infection for same reason acute bloody diarrhoea - can be caused by E. coli and taking Loperamide increases chance of developing HUS

what are the side-effects of Loperamide?

Nausea, flatulence, headache, dizziness

what are the possible interactions with Loperamide?

when taking other opioids there is risk of toxicity eg codeine phosphate

what are the three types of laxative?

bulk forming eg methyl cellulose osmotic eg lactulose stimulant eg Senna

how do stimulant laxatives work?

most common type increase water and electrolyte secretion which increases colonic volume and increases peristalsis

what are the indications to take laxatives?

general: constipation, faecal impaction osmotic: hepatic encephalopathy (stops absorption of ammonia)

what are the side effects of laxatives?

abdominal pain and cramping diarrhoea nausea hypokalaemia

what are the contra-indications to taking laxatives?

Intestinal obstruction (could induce perforation) and undiagnosed abdo pain osmotic: can cause big fluid shifts. careful in Heart failure, ascites, electrolyte imbalance

what are the interactions with laxatives?

Digoxin, diuretics, increase effect of warfarin

what class of drug are Mesalazine (better one) and Sulfalazine?

aminosalicylates

how do aminosalicylates work?

release 5-aminosalicylic acid - this has antiinflammatory and immunosuppressant actions topically on the gut

what are the indications to take mesalazine?

mild UC

what are the contraindications to take mesalazine?

aspirin hypersensitivity, hepatic impairment

what are the side-effects of mesalazine?

``` GI upset (Diarrhoea, nausea, vomiting, abdo pain) rarely cause leucopenia and thrombocytopenia and renal impairment ```

what are the possible interactions of mesalazine?

PPIs - may cause premature release of capsule content

what class of drug are metaclopramide and domperidone?

antiemetic - Dopamine receptor antagonist

how does metaclopramide (D2 receptor antagonist) work?

promotes relaxation of gut and stomach | Binds to dopamine receptors in CNS preventing nausea and vomiting triggered by most stimuli

what are the indications to take metaclopramide?

nausea and vomiting (esp in context of reduced gut motility)

what are the contra-indications of metaclopramide?

avoid in children and young adults (more common extrapyrimidal side effects) GI obstruction/perforation

what are the side-effects of metaclopramide?

diarrhoea, Extrapyramidal effects (drug induced movement disorders including acute and tardive symptoms) - domperidone does not cuase this - does not cross blood brain barrier hyperprolactinaemia, galactorrhoea, gynecomastia, menstrual changes, dry mouth

what are the possible interactions with metaclopromide?

antipsychotics - inc risk of extrapyramidal antagonise effect of dopamine based parkinson drugs paracetamol and aspirin (increase rate of absorption)

what class of drug is cyclizine?

antiemetic - Histamine receptor antagonist

what are the indications for taking cyclizine?

nausea and vomiting (esp with motion sickness and vertigo)

how does cyclizine work?

Histamine is main receptor in vomiting centre of the brain along with Ach. Cyclizine blocks both

what are the side effects of cyclizine?

drowsiness dry mouth and throat tachycardia + palpitation

what are the contra-indications to taking cyclizine?

sedating effect - avoid in hepatic encephalopathy | prostatic hypertrophy - can cause urinary retention (anticholinergic side-effects)

what are the interactions of cyclizine?

opioids/benzodiazepines - increased sedation

when is ondansetron useful?

sickness in chemotherapy