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Constipation

Constipation

Aetiology

� Diet: low fibre, low fluid intake

� Reduced mobility

� Drugs: opioids, anti-cholinergics, anti-depressants, anti-parkinson’s therapy

Normal fibre intake: 10-20g/day

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Incidence

� ± 12m prescription in the UK/annum

� Prevalence: 8.2%

� Men: 39%, women: 52% in surveys

� Constipation increases with age

Causes of severe/refractory constipation

A. Slow colonic transit

N: 35hrs. >72 hrs = abnormal

Idiopathic colonic inertia – women

B. Pelvic floor dysfunction (=outlet disorders)� Excessive straining

� Sense of incomplete evacuation

� Need for digital pressure: vagina perineum

� Digital disimpaction

C. Irritable bowel syndrome� Abdominal pain

� Bloating

� Sense of incomplete evacuation

� Normal stool: 70-85% water ≥ 3/week

� Rome II criteria 2 or more of the following

symptoms for at least 12 w in the preceding yr:

� Straining at defecation on at least a ¼ of occasions

� Stools lumpy/hard – at least 25% of times

� Sensation of incomplete evacuation – 25% of times

� 3 or less bowel movements per week

Diagnosis

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Management

� Diet: fluid, fibre rich diet

� Avoidance of constipating drugs

ONLY THEN CONSIDER MEDICATION!

Laxatives

� Bulk-forming

� Stimulant

� Faecal softeners

� Osmotic laxatives

� Bowel cleansing solutions

� Oral

� Rectal suppositories

General contraindications: intestinal perforation and obstruction

Bulk-forming laxatives

� Increase faecal mass which stimulates peristalsis

� Bulk/softness/hydration dependant on fibre

� Ensure adequate fluid intake (obstruction)

� Effect can be delayed by a few days

� Try dietary fibre� Wheat bran, oat brasn, bran biscuits

� Pectins/hemicellulose (fruits, vegetables)

� Ispaghula (Fybogel, Isogel)

� Methylcellulose (Cevelac)

� Sterculia (Normacol)

� Contraindication: intestinal obstruction, colonic atony, faecal impaction

� Side effects: flatulence, abdominal distension, GI obstruction, rarely hypersensitivity

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Stimulant laxatives

Increase intestinal motility

� Diphenylmethane derivatives� Sodium picosulfate, hydrolyzed by bacteria to active form, effects vary

� Bisacodyl (Dulco-lax), usually 5-10mg nocte

� Anthraquinone Laxatives� Require activation in colon (bacteria), onset of action delayed (6-12 hours)

� Senna (Senokot), plant derivative

� Danthron (Co-danthramer) possibly carcinogenic, only use in terminally ill

� Docusate sodium

� Stimulant and softening

� Glycerol suppositories

� (Parasympathomimetics such as bethanecol, neostimin rarely used)

Side effects: diarrhoea, hypokalemia

Osmotic laxatives

Osmotically mediated water retention

� Nondigestible sugars and alcohols

� Synthetic disaccharide, resists intestinal disacharidase

� Draw water in osmotically, not absorbed

� Lactulose

� Use: elderly, opioids, hepatic encephalopathy (↓ ammonia production)

� Magnesium salts

� Phosphates (rectal, Fleet)

� Sodium citrate (rectal, Micralax Micro-enema)

� Polyethylene Glycol-Electrolyte Solutions – Macrogels

� Sequester fluid in bowel, poorly absorbed

� Movicol

Faecal softeners - Emollients

Sodium docusate (stimulant and softening)

� Arachis oil enema for impacted faeces

� Liquid paraffin (oral solution)

Side effects: anal irritation, interference with absorption of fat soluble

vitamins, granulomatous reactions

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Bowel cleansing solutions

� Before surgery, colonoscopy and radiological

examinations

� E.g. Fleet, Klean-Prep, Picolax

� Contraindications: obstruction, GI-ulceration,

perforation, CCF, toxic colitis or megacolon,

ileus

� Side effects: nausea, bloating, cramps,

vomiting

Prokinetic drugs

� Metoclopramide

� Domperidone

� Cisapride

� These are agonists at 5-HT4 receptors in enteric nervous system.

� They facilitate cholinergic transmission and prokinesia, increasing gastric emptying

� Decrease small bowel transit time

� Increase gastro-oesophageal sphincter tone

Antimuscarinic antispasmodic agents

� Atropine and belladonna alkaloids and synthetic antimuscarinic agents

� Relief muscle spasm

� Hyoscine: belladonna alkaloid

� Synthetic tertiary amines:

o Dicycloverine

o Mebeverine

� Synthetic quaternary ammonium compounds:

o Propantheline

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Antipropulsives

� Reduce gastrointestinal motility

� Symptomatic management of diarrhoea

� Do not use in children

� NB!! Fluid and electrolyte replacement

� Treat underlying cause of diarrhoea

� Diphenoxylate

� Loperamide

Diphenoxylate

� Diphenoxylate and atropine in Lomotil®

� Non-analgesic derivative of opioids

� Derivative of Pethidine

� Opiate-like constipating effects

� Reduces peristalsis

� Atropine added to discourage abuse

Loperamide

� Structurally related to pethidine

� Binds to opioid receptors presynaptically in

enteric nervous system, inhibiting acetyl

choline release

� Slows gastrointestinal motility by inhibiting

contractions

� Does not cross BBB

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Opioids

� Codeine and Morphine

� Causes “spastic paralysis”

� Increased segmental contraction and reduced

peristalsis

� Reduction in propulsion increases absorption

of water and contents of intestinal tract thicken

Medications that can cause

constipation

� Anticholinergics

� Iron

� Diuretics

� Opiates

� Purgative abuse

� Antidepressants

� Aluminium salts

� Calcium salts

� Calcium channel blockers