GI Flashcards
Gaviscon
Indication: gastric acid
- GORD
- ulcers (NSAIDs, smoking, alcohol, H.pylori)
Class: alginates and antacids
Action:
- antacids buffer stomach acid
- alginic acid increase stomach content viscocity and reduce reflux
Preperation:
Sodium alginate + aluminium hydroxide/magnesium carbonate
Adverse effects:
- magnesium carbonate can cause diarrhoea
- aluminium hydroxide can cause constipation
Warnings:
- renal failure - high Na+ and K+
- diabetes - high sucrose content - hyperglyceamia
Interactions:
- can reduce absorption of many drugs
- increase urine alkalinity can increase aspirin excretion
Lansoprazole/omeprazole
Indication: gastric acid
- alongside long term NSAID or steroid
Class: PPI
Action:
- irreversibly inhibit H+/K+ ATPase in parietal cells
- final stage - v.significant reduction
Adverse effects:
- GI - pain, constipation, diarhhoea
- headache, dizziness, dowrsiness, confusion
Warnings:
- mask symtptoms of gastro-oesaphageal cancer
- osteoprosis - fracture risk
Interactions:
- omeprazole is a CYP inhibitor - reduce clopidogrel action
- PPIs increase effecrs of warfarin and phenytoin
Ranitidine
Indication: gastric acid
Class: H2 recepptor antagonist
Action: inhibits histamines controbution to proton pump activation
Adverse effects:
- diarrhea
- headache
Warnings:
- mask symptoms of gasto-oesophageal cancer
- renal impairement
Large scale recall due to possible carcinogenic contaminant - lansoprazole is the alternative
H.Pylori treatment
One week triple therpay
Lansoprazole + clarithromycin + amoxicillin
Metronidazole for pencillin allergy
Mesalazine
Indication: UC
Class: aminosalicylates
Action:
- release of 5-ASA - antinflamatory
- action at the colon (enteric coated tablet limits gastric breakdwon)
Adverse effects:
- nausea, dyspepsia
- leukopenia (rare)
Warnings:
- hypersensitivty (similar to aspirin)
Interactions: enteric coated tabelts break down quicker in presence of PPI due to increased pH
Other:
- mesalazine - no role in RA
- sulfasalazine - more side effects so used less in UC but sulfa group good for RA
Hyoscine hydrobromide
Indication: antiemetics
- bowel obstruction
Class: muscarinic receptor antagonist
- act on vestibular nuceli and CTZ
Side effects:
- sedation
- memory
- glaucoma
- parasympatehtic - dry mouth and constipation
(Exploit side effects in neuro disorders to reduce salivation)
Cyclizine/promethazine/diphenhydramine
Indication: antiemetic
- opioid induced
- motion sickness - long journeys
- promethazine for morning sickness
Class: H1 receptor antagonist
- act on vestibular nuclei and CTZ
Action: inhibits histaminergic signals from vestibular system to CTZ in the medulla
Adverse effects:
- sedation
- excitation
- parasympathetic - dry mouth, constipation, urinary retention
- cardiac toxicity
Warnings:
- cyclizine in old ladies and children - disorientation + confusion
Ondansetron
Indication: antiemetic
- everone - 1st line treatment
- opioid induced
Class: serotonin (5HT3) receptor antagonist
- act on visceral afferents in the gut + CTZ
Action:
- peripherally reduces GI motility and secretions
- centrally inhibits the CTZ
Adverse effects: Uncommon
- constipation
- headache
- increased liver enzymes
- long QT
- extrapyramidal effects - dystonia, parkinsonism
Metoclopramide/domperidone
Indication: antiemetic
- impaired gastric emptying
- GORD
- ileus
- lactation in breastfeeding (domperidone)
Class: D2 recpetor (dopamine) antagonist
- act on visceral afferents in the gut
Action: PROKINETIC
- increases Ach at muscuranic recptors in the gut
- promotes gastric emptying
> increase tone of LOS
> increase tone + amplitude of contractions
> decrease tone of pylorus
- increases peristalsis
Adverse effects:
- galactorrhoea (prolactin release)
- extra-pyramidal effects - dystonia, parkinsosim
- sudden cardiac death (DOMPERIDONE ONLY)
Chlorpromazine/prochlorperazine/ haloperidol
Indication: antiemetics + antipsychotics
- Menieres
- motion sickness, vertigo
- prochlorperazine in pregnancy
- haloperidol for chemotherapy and palliation
Class: D2 receptor antagonists
- act on the CTZ
- may alos block H1 and muscuranic receptors
Side effects:
- extrapyramidal
- sedation
- hypotension
Dexamathasone/methylprednisolone
Indication: antiemetic
- perioperative nausea - at induction of anaesthesia
- cehmotherapy and pailliation
Class: corticosteroid
- act on CTZ
- properties of D2 receptor antagonists
Side effcects: CORTICOSTEROIDS
- insomnia
- increase appetite
- increase blood sugar
Nabilone
Indication: anitemetic
- last line chemotherapay
Class: cannabinoids
- acts on CTZ
Adverse effects:
- dizziness and drowsiness
Aprepitant
Indication: antiemetic
- chemotherapy - delyaed emesis
Class: neurkinin 1 receptor antagonist
- acts on CTZ
Action:
- prevents action of substance P at CTZ and peripheral nerves
- boosts effects of 5HT3 receptor antagonist
- anxiolytic and antidepressant
Adverse effects:
- headache
- diarhoea/constipation
- stevens-johnson syndrome
Treatment for motion sickness
1st line = hyoscine hydrobromide
Cinnirazine has fewer side effects (dont want sedative effect on driver)
Treatment for GORD/ileus
Try NG tube
Prokinetics - domperidome (increase peristalsis)
NOT in bowel obstruction - peristalsis against obstruction in painful and risk of perforation
Treatment for surgical bowel problems e.g obstruction
Ondansetron (5HT3 receptor antagonist
And/or
Cyclizine (H1 receptor antagonist)
Then
Dexamethasone (corticosteroid)
Treatment for hyperemesis gravidarum
Promethazine (H1 antagonist) or prochlorperazine (D2)
Then
Metoclopramide (D2 antagonist)
Then
Ondansetron (5HT3 antagonist)
- increased risk of cleft palette
Treatment for chemotherapy
Low risk: dexamethasone (+ metoclopramide if needed)
Moderate: dexamethasone + ondansetron (+ metoclopramide if needed)
High: dexamethasone + ondansetron + aprepitant (+ metoclopramide if needed)
Loperamide/codeine/morphine
Indication: diarrhoea
- loperamide GI specific
- codeine/morphine when pain too
Class: opioid receptor agonsit
Action:
- mod receptors in the myenteric plexus
- decrease tone of longitudinal and circular smooth muscle
- reduces peristalsis but increases segmental contraction
- decreases colonic mass movement by supressing gastrocolic reflex
Adverse effects:
- parayltic ileus
- nausea and vomiting
- sedation
- addiction
Lactulose/movicol
Indication: constipation
Class: osmotic laxatives
Actions:
- Lactulose draw fluid in
- macrogols retain the fluid they came with
Bisacodyl, senna, docusate sodium
Indication: constipation
Class: stimulant laxatives
Action:
- increase intestinal motility
- docusate is a stimulant and stool softner
Adverse effects: glycerin can cause rectal irritation and lubrication
Ispaghula husk/methylcellulose
Indication: constipation/diarrhoea
Class: bulk forming laxatives
Action: medicinal fibre
- softens constipation
- bulks diarrhea
Docusate sodium/glycerin suppository
Indication: constipation
Class: stool softner
Action:
- decrease surface tension of stool
- increase penetration of fluid into stool
