Bowel Preparation Flashcards
1
Q
Osmotic laxatives (lactulose, macrogol, phosphate enema)
Common indications
A
- Constipation and faecal impaction
- Bowel preparation prior to surgery or endoscopy
- Hepatic encephalopathy
2
Q
Osmotic laxatives (lactulose, macrogol, phosphate enema)
MOA
A
- These medicines are based on osmotically active substances (Sugars and alcohols) that are not digested or absorbed and which therefore remain in the gut lumen
- They hold water in the stool, maintaining its volume and stimulating peristalsis
- Lactulose, in particular, also reduces ammonia absorption
- It does this by increasing gut transit rate and acidifying the stool, which inhibits the proliferation of ammonia-producing bacteria
- This is helpful in patients with liver failure, in whom ammonia plays a major role in the pathogenesis of hepatic encephalopathy
3
Q
Osmotic laxatives (lactulose, macrogol, phosphate enema)
Important adverse effects
A
- Flatulence, ab cramps and nausea are common adverse effects, although they may decrease with time
- As with other laxatives, diarrhoea is a possible complication
- Phosphate enemas can cause local irritation and electrolyte disturbance
4
Q
Osmotic laxatives (lactulose, macrogol, phosphate enema)
Warnings
A
- Osmotic laxatives are contraindicated in intestinal obstruction as there is a risk of perforation
- Phosphate enemas can cause significant fluid shifts so should be used with caution in HF, ascites and when electrolyte disturbances are present
5
Q
Osmotic laxatives (lactulose, macrogol, phosphate enema)
Important interactions
A
- There are no significant adverse drug interactions with osmotic laxatives although the effects of warfarin may be slightly increased
6
Q
Osmotic laxatives (lactulose, macrogol, phosphate enema)
Prescription
A
- Orally administered osmotic laxatives should generally be prescribed in the regular section of the drug chart
- For example, when treating constipation or faecal impaction you might prescribe lactulose 15mL BD, titrating this to response
- Be aware that it may take a few days for an effect to be seen, as the drug needs to pass through the GI tract to the colon
- When using a phosphate enema to treat faecal impaction, prescribe it in the OD or as-required section for rectal administration
- The dose should not usually exceed one enema in 24hours
- For bowel preparation, you should refer to a local protocol for prescribing advice
- When using lactulose to treat or prevent hepatic encephalopathy, you might start with 30-50mL (Doubled in constipation) TDS, aiming for the patient to produce three soft/loos stools daily
7
Q
Osmotic laxatives (lactulose, macrogol, phosphate enema)
Administration
A
- Osmotic laxatives may be taken with or without food
- Oral solutions can be taken as they are or diluted in another liquid; powdered forms are dissolved in water
- Enema are administered with the patient lying on their side, as a rectal examination
- They should stay in this position for a few minutes or until they need to open their bowels
8
Q
Osmotic laxatives (lactulose, macrogol, phosphate enema)
Communication
A
- Explain that you are offering treatment with a laxative that will hopefully make their stool softer and easier to pass
- To work, it requires them to drink plenty of water: they should aim to have at least 6-8 glasses of liquid per day
- Mention that side effects such as abdominal cramps and flatulence can occur, but these may get better overtime
- Advise that the dose should be adjusted to maintain comfort
- If they are regularly passing more than 2 or 3 soft stools per day, the dose should definitely be reduced or the laxative stopped (Unless being used for hepatic encephalopathy)
9
Q
Osmotic laxatives (lactulose, macrogol, phosphate enema)
Monitoring
A
- When treating inpatients, a stool chart is useful to monitor the effects of treatment
- This is particularly important when treating hepatic encephalopathy, where you should also monitor electrolytes
