Irritable bowel syndrome Flashcards
What is the aetiology / causes of IBS?
Exact cause of IBS is NOT understood
- Food intolerances (e.g. Lactose/Gluten) are precursors to developing IBS
- No lesions are present (i.e. gut is not damaged/diseased)
- Post infective bowel dysfunction, gut hypersensitivity, altered colonic motility and heightened pain sensation all implicated
(1 in 6 patients developed IBS who have recently recovered from gastroenteritis) - Stress commonly implicated
What is the pathophysiology of IBS?
Structurally the gut is normal - therefore not detectable using standard tests.
However IBS is a ‘functional’ GI disorder
- Blood tests, stool samples, colonoscopy may be used to rule out other conditions
- Functional conditions require symptom management
What are the symptoms of IBS?
- Abdominal cramping
- Diarrhoea/constipation/alternating
- Flatulence (gas)
- Bloating
- Urgency to defecate
In addition:
- Acid indigestion
- Nausea
- Lethargy (lack of energy, sluggishness)
- Eating may worsen symptoms
- Passing mucus in stools
How is IBS diagnosed? What factors are considered?
- Abdominal pain present for at least 6 months
- Relieved by defecation
or - Increased/decreased bowel frequency or stool form
+
2 of the following signs and symptoms: - Abdominal bloating/distension
- Altered stool passage (straining, urgency, incomplete evacuation)
- Worsened by eating
- Passing mucus
How is IBS diagnosed in secondary care?
In secondary care, the Rome IV criteria are sometimes used- IBS-C, IBS-D, IBS-M, IBS-U
- Abdominal pain 1 day per week in last 3 months
- Symptoms began at least 6 months prior to diagnosis
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2 of the following symptoms: - Symptoms related to defecation
- Change in stool frequency
- Change in stool form
What are the treatment options for IBS?
- Antispasmodic drugs
- Antidepressants
- Laxatives
- Loperamide
- Linaclotide
What antispasmodic drugs are used in the treatment of IBS?
Preferable to use as they are direct acting smooth muscle relaxants:
- Alverine Citrate 60-120mg up to TDS
- Mebeverine 135mg TDS (20mins before food) or 200mg BD for MR preparations
- Peppermint oil capsules, 1-2 caps up to TDS
Hyoscine butylbromide and Dicycloverine can also be used but they tend to have more antimuscarinic effects
- Contraindicated in intestinal obstruction or paralytic ileus because we are slowing down motility.
How are antidepressants used in the treatment of IBS?
Use of antidepressants is unlicensed for people with IBS pain.
Usually given to people who didn’t respond to typical treatments.
Doses given are lower than you would see for mental health uses e.g. Amitriptyline 10-30mg at night
SECOND LINE - SSRI: (Unlicensed)
- E.g. Sertraline, Citalopram, Fluoxetine
These medications would have a pain modulatory effects/peripheral effects on GI function which is the benefits of this medication
Counsel patients as they may be shocked when reading patient info leaflet
How are laxatives used in the treatment of IBS?
- Laxatives are used for IBS-C - prominently constipation symptoms
- Laxatives from any class can be used apart from Lactulose
- Lactulose can increase gas production and can worsen symptoms
- Dose should be titrated according to symptoms
- AVOID PROLONGED STIMULANT LAXATIVE USE
How is loperamide used in the treatment of IBS?
- Loperamide is used for IBS-D - prominently diarrhoea symptoms
- P/GSL versions of loperamide can be used for acute diarrhoea in IBS but only for patients >18 years old
- MUST have been DIAGNOSED with IBS
- Only for attacks lasting up to 48 hours (refer if longer)
- Can be used for 2 weeks maximum, as long as individual bouts are less than 48hours.
How is Linaclotide used in the treatment of IBS?
Linaclotide is used for moderate to severe IBS-C in adults - constipation symptoms
- Patient must’ve had IBS-C for at least 12 months
- Should only be used if max tolerated dose of laxatives haven’t worked
- 290mcg once daily 30mins before food
- Avoid in GI obstruction due to its laxative effect/IBD
What is the pharmacology/mechanism of action of antispasmodics?
- Antispasmodics act on smooth muscle cells
- Works by blocking voltage operated sodium channels
- Which prevents the build up of intracellular calcium
- Reduction of calcium = reduction in contractility of smooth muscles
- This reduces symptoms of colonic hypERmotility
What is the pharmacology/mechanism of action of Linaclotide?
- Linaclotide is a GC-C agonist
- GC-C activation leads to increased production of cGMP
- Increased cGMP stimulates the CFTR ion channel
- CFTR ion channel increases secretion of chloride and bicarbonate into the intestinal lumen
- This increases the moisture content of the lumen hence:
- GI transit increased
What are the red flag symptoms for IBS indicating referral?
- Unintentional weight loss
- Unexplained rectal bleeding
- Family history of bowel/ovarian cancer
- Loose stools for OVER 6 weeks in patients OVER 60 years old
- Anaemia
- Elevated inflammatory markers
- Abdominal/rectal masses
