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Treatment of Constipation (Bulk-forming laxatives (Drugs: Ipaghula,…
Treatment of Constipation
Bulk-forming laxatives
Drugs:
Ipaghula, psyllium, sterculia
Mechanism of action:
They are polysaccharide polymers which are not broken down by digestion and attack to stool
They absorb water and increase the volume, bulk & moisture of stools, thereby distending the bowel
Distension of the wall stimulates peristalsis via stretch receptors
Route of administration & onset of action:
Taken orally, 48-72 hour onset of action (not for acute relief)
Clinical use:
Mild constipation, small hard stools, and long-term control
Better for use in normal transit time
Ensure adequate fluid intake to avoid intestinal obstruction
Adverse effects:
Flatulence, bloating, abdominal discomfort
Precautions:
Intestinal obstruction (partial or complete) - Contraindicated
Colonic atony - Contraindicated
Dysphagia - Avoid use, oesophageal obstruction may occur
Fluid restriction, immobility - Avoid use
Osmotic laxatives
Drugs:
Glycerol suppositories, lactulose, sorbitol, macrogol laxatives, saline laxatives
Mechanism of action:
Osmotic laxatives are poorly absorbed and therefore stay in the intestinal lumen
They exert an osmotic force causing water to move into the intestinal lumen thus adding volume and fluid to stool contents
Glycerol suppositories:
Rectal administration
Onset of action is 5-30 minutes
Well tolerated local effect
Lactulose, sorbitol and macrogol laxatives:
Oral administration
Onset of action is 1-3 days
Adverse effects include nausea, vomiting, diarrhoea, distension, cramps, pain
Saline laxatives:
Oral or rectal administration
Onset of action is 0.5-3 hours (oral) or 2-30 minutes (rectal)
Adverse effects include nausea, bloating, fluid and electrolyte disturbance
Stimulant laxatives
Drugs:
Bisacodyl, senna
Mechanism of action:
Precise mechanism of action is unknown
They may increase electrolyte and therefore water secretion by the mucosa and directly irritate intramural sensory nerve plexi endings
Clinical use:
Severe constipation unresponsive to bulking agents or osmotic laxatives
Short-term use preferred
May be long term for constipation due to spinal damage, chronic neuromuscular disease and people taking opioids
Route of administration & onset of action:
Oral: 6-12 hours
Rectal: 5-60 minutes
Adverse effects:
Diarrhoea, cramping, nausea
Stool-softening laxatives
Drugs:
Docusate, poloxamer, liquid paraffin
Mechanism of action:
Soften the stool and ease its passage
Docusate
and
poloxamer
are surfactants (allow the water and oil of stool to mix better)
Liquid paraffin
is a lubricant
Adverse effects:
Well tolerated
Route of administration and onset of action:
Oral: 1-3 days
Clinical use:
Used to treat constipation (usually with a stimulant or osmotic laxative) and to prevent straining after rectal surgery and in acute perianal disease
Little value as single agents in chronic constipation