Liver Disease/Dyspepsia/Altered Bowel Habit Flashcards
What are the main problems in prescribing with liver impairment?
- Hypoproteinemia
- Impaired drug metabolism
- Reduced clotting
- Hepatic encephalopathy
- Fluid overload
- Hepatotoxic drugs
What is the resulted of hypoproteinaemia secondary to liver disease?
Low albumin is associated with reduced protein binding and increased toxicity of drugs which are highly protein bound
eg. phenytoin, prednisolone
Which drugs undergo the majority of their 1st pass metabolism in the liver? Why is this relevant?
Aspirin, Lidocaine, GTN, levodopa, morphine, salbutamol
If the liver is severely damaged, drug metabolism of these will be impaired
Which drugs precipitate hepatic encephatlopathy?
Sedatives, opiods, diuretics, drugs that cause constipation
Which drugs cause fluid retention?
NSAIDs, steroids
Which drugs are hepatotoxic?
Paracetamol, isoniazid, statins, methotrexate, phenytoin, aspirin, alcohol, COCP, abx
What is hepatic drug clearance? What 4 variables does it take into account?
The volume of blood perfusing the liver that is cleared of the drug per unit time.
Takes into account
Q - blood flow
F - fraction of free drug
Clint - intrinsic ability of liver to metabolise drug
Extraction ratio - % of drug removed from blood in the liver
What is a high extraction ratio?
> 0.7 - high first pass effect, most of the drug removed in the liver
If a patient with known liver disease is given a drug, how should the dose be adjusted?
What is the equation?
LOWER DOSE as the liver will no longer be able to metabolise drug so more will go into systemic circulation
New dose = (normal dose x (1-ER))/100
What is the pathophysiology of dyspepsia?
INCREASED ACID PRODUCTION (gastrin, pepsin, H. pylori, histamine)
DECREAED MUCOSAL PROTECTION (mucin, Cox, H. yplori)
What is the main cause of dyspepsia?
H. pylori infection
What else can cause dyspepsia?
NSAIDS Steroids (if not given alongside PPI) Alcohol Smoking Stress Hypersecretory states (Zollinger-Ellison)
How should an <55yo with dyspepsia be investigated?
Test for H.pylori with faecal antigen, C13 urea breath test
Prescribe 4 wk PPI in the mean time
How should an >55yo with dyspepsia be investigated?
Urgent endoscopy (DONT PRESCRIBE PPI!) and CLO test by biopsy
How should ulcer secondary to H.pylori infection be treated?
Triple therapy for 1/2 weeks
PPI + amoxicilllin + clarithromycin/metronidazole
Following triple therapy to eradicate h.pylori, how can peptic ulcer disease be further managed?
Antacids (aluminium, magnesium)
H2 receptor antagonist (cimetidine) and PPI for 8 weeks
Stop NSAID use
If gastric ulcer, repeat endoscopy at 8 weeks
In which cases is surgery indicated for PUD?
Failed management of upper GI bleed
Complications of PUD
How does PPI work?
Irreversible inhibition of H/K ATPase to stop H+ secretion from parietal cells
How do H2RAs work?
Block action of histamine on parietal cells
How do antacids work?
Raise stomach pH, bind to an inactivate pepsin
What are the symptoms of upper GI bleed?
Malaena - sticky black stools
N&V
Upper abdo pain
Coffee ground vomit
What is the Blatchford score for?
Evaluation of need for intervention after UGI bleed
Score > 0 indicates need for transfusion, endoscopy, surgery
What is the Rockall score for? What factors does it take into account?
Measures risk of mortality and re-bleed following an endoscopy
Looks at age, shock, comorbidities, endoscopic signs, diagnosis
How is an acute UGI bleed managed? (conservative, medical, surgical)
- IV fluids
- Assess haemodynamic status
- Calculate blatchord score
- Offer endoscopy (severe = now, non-severe = in 24h)
- Endoscopic therapy (clips, adrenaline, probe)
- Monitor and calculate Rockall score
- STAT omeprazole then IV for 72 hrs
Following discharge from hospital, how should an UGI bleed be managed?
- High dose PPI for 2 months
- Stop NSAIDS
- Repeat endoscopy at 6-8 weeks
In patients with CVS risk factors, should COX2 inhibitors or NSAIDS be used?
NSAIDS - cox2 are prothrombotic
In patients with GI disease, should COX2 inhibitors or NSAIDS be used?
COX2 - these are selective so less likely to damage the gut
What can cause acute diarrhoea?
Gastroenteritis C. diff IBD IBS Pancreatitis Colitis Alcoholic gastritis
What special tests can be done in the setting of acute diarrhoea?
Flexi sig, serum amylase, faecal calprotectin (sign of inflammation), elastase, CT
What drug is used for diarrhoea, and when is it contraindicated?
Loperamide (anti motility agent)
Contra: severe UC, toxic megacolon, bloody stool
What can cause constipation?
Primary: Hirschprungs, rectocoele
Secondary: medication, neurological, low fibre, mechanical, metabolic, endocrine (hypothyroid, diabetes)
Which meds cause constipation?
Opiates, CCBs, iron
In what case does constipation require investigation?
> 40yrs, recent change in bowel habit and associated symptoms
What investigations can be done for constipation?
BLOODS: FBC, U&E, LFT, TFTs, bone, PSA, haematinics
IMAGING: AXR, CT
SPECIAL: OGD/colonoscopy
What are the 4 types of laxatives? Give examples
- BULK FORMING
- STIMULANT
- OSMOTIC
- STOOL SOFTENERS
Give an example of a bulk forming laxative
Bran
Isphagula husk
Give an example of a stimulant laxative
Senna
Bisacodyl
Give an example of an osmotic laxative
Macrogol
Movicol
Lactulose
Give an example of a stool softener
Liquid paraffin
Docusate sodium
A patient has constipation related to poor diet and needs long term laxatives. What is the best choice?
Bulk forming (bran, ispaguhla husk)
A patient has renal failure. Which laxatives should not be used?
Osmotic (macrogol, lactulose)
A patient on morphine has constipation. What laxative should be used and why do you use with care?
Stimulnat (senna, bisacodyl) - risk of cathartic colon as they are very strong
A patient has had recent surgery but is not yet constipated. What should be used to prevent constipation?
Stool softeners (docusate sodium, liquid paraffin)
