Gastrointestinal Flashcards
Name 2 osmotic laxatives and 2 indications for their use:
- lactulose, macrogol, phosphate enema
- for constipation and faecal impaction
- for bowel preparation prior to surgery/endoscopy
- for hepatic encephalopathy
MOA of osmotic laxatives
- based on osmotically active substances that are not digested/absorbed so …
- …and with regards to help with liver failure pts… lactulose….
- remain in the gut lumen
- so they hold water in the stool, maintaining the volume and stimulating peristalsis
- lactulose also reduces ammonia absorption by increasing gut transit rate and acidifying the stool which inhibits the proliferation of ammonia-producing bacteria
- helpful in pts with liver failure
3 SEs of osmotic laxatives:
e.g. lactulose, macrogol, phosphate enema
- flatulence, abdo cramps, nausea
- diarrhoea
- phosphate enemas can –> local irritation and electrolyte disturbances
osmotic laxatives are contraindicated in ____ ___ as there is a risk of perforation.
Phosphate enemas can cause signif fluid shifts so use with caution in pts with : __ ___, ____ and when they have _____ disturbances
CI: INTESTINAL OBSTRUCTION
Caution: HF, ascites, electrolyte
For osmotic laxatives to work how much should the patient drink?
-plenty! 6-8 glasses of liquid/day+
Why are phosphate enemas reserved for 2nd line? What should be tried first for faecal impaction?
- try a glycerol suppository (stimulant laxative) - less likely to cause electrolyte disturbance
- phosphate enemas are irritant and given with a signif fluid volume 100ml+ so are uncomfortable
Senna, bisacodyl, glycerol suppositories and docusate sodium are examples of what class of laxatives? Indicated for what?
- Stimulant laxatives
- for constipation
- as suppositories for faecal impaction
How do stimulant laxatives exert their action? e.g.Senna, bisacodyl, glycerol suppositories and docusate
- increase water and electrolyte secretion from colonic mucosa so increase the volume of colonic content and stimulate peristalsis
- direct pro-peristalsis action
2 SEs of stimulant laxatives eg. Senna, bisacodyl, glycerol suppositories and docusate
- abdo pain or cramping
- diarrhoea
- prolonged use can –> melanosis coli (reversible pigmentation of intestinal wall)
1 CI and 1 caution for use of stimulant laxatives e.g. Senna, bisacodyl, glycerol suppositories and docusate
CI: INTESTINAL OBSTRUCTION (risk of perforation)
Caution: rectal preparations are usually avoided if haemorrhoids or anal fissures present
How much water to be drunk with stimulant laxative administration?
-6-8 glasses per day
Gaviscon and Peptac are used for GORD/dyspepsia relief. What is the difference in MOA of antacids vs alginates?
Antacids: work by buffering stomach acids
Alginates: act to increase the viscosity of the contents so reduces reflux into oesophagus, they form a floating ‘raft’ separating contents from GOJ preventing mucosal damage
What do some preparations of antacids/alginates contain that can worsen hyperglycaemia in DM patients?
-sucrose
The divalent cations in compound alginates can bind to other drugs reducing their absorption, therefore how can you minimise the risk?
Suggest 3 medications affected
- separate doses by 2hrs from the other meds
- affected meds: ACEi, cephalosporins, ciprofloxacin, tetracyclines, bisphosphonates, digoxin, levothyroxine, PPIs
What medication class can increase the excretion of aspirin and lithium and why?
- Antacids/alginates
- as they contain sodium bicarb/calcium bicarb/mg/al salts
- they increase the alkalinity of urine so increase the excretion of those meds
