Constipation is an unsatisfactory defecation distinguished by difficult stool passage, infrequent stools or both.
Difficult stool passage may include straining, feeling of difficulty in passing stool, incomplete evacuation, lumpy/hard stools, prolonged time to defecate, need for manual maneuver to pass stool, abdominal discomfort and feeling of anorectal blockade.
Chronic constipation is considered when symptoms of constipation have existed ≥3 months.
Symptoms of chronic constipation may be due to dysfunction of intestinal motility, visceral sensitivity, anorectal musculature or the enteric nervous system.

Principles of Therapy

  • Treatment should be instituted primarily to obtain regular and complete bowel movements and secondarily to palliate symptoms of anorexia, bloating, and abdominal pain
  • Efficacy, safety and drug dependency should all be considered when deciding on which laxative to suggest
    • Bulk-producing and osmotic laxatives are generally the 1st choice
    • Newer agents for management of chronic constipation may be considered after a therapeutic trial of fiber supplementation and laxatives
    • Propulsives can be used for slow transit constipation


Bulk-Producing Laxatives

  • Eg Ispaghula (Psyllium), Methylcellulose, Sterculia
  • Increases bulk of stool, decreases colonic transit time, increases gastrointestinal (GI) motility
  • Psyllium has been shown to increase stool frequency in patients with chronic constipation
  • Therapy should be started with 2 daily doses in the morning and evening with fluids; dose may be adjusted after 7-10 days
  • Patients should be informed that immediate response should not be expected and that bloating and abdominal distension may occur especially at the start of fiber therapy but may decrease over time or with a dose reduction

Osmotic Laxatives

  • Eg Lactulose, Milk of Magnesia, Sorbitol, PEG, Na chloride, Na phosphate
  • Poorly absorbed or nonabsorbed substances which cause secretion of water into the intestines osmotically increasing intraluminal fluids that ease transport of colonic content
  • Osmotic laxatives may be attempted if an increase in fiber fails to relieve symptoms
  • Lactulose has been shown to be effective at increasing stool frequency and stool consistency in patients with chronic constipation
    • May have a prebiotic effect ie growth of colonic probiotic bacteria is supported that could bring about bowel function improvement
  • Polyethylene glycol (PEG) has been demonstrated to be useful for fecal disimpaction in the elderly
  • Combination therapy may also be considered with either a stimulant or an enterokinetic agent (eg Prucalopride) plus an osmotic agent
  • Patients may be instructed to adjust dose so that soft, but not liquid stools, are achieved and that these agents may take several days to work

Stimulant Laxatives

  • Eg Bisacodyl, Na picosulfate, Senna, Glycerin
  • Active metabolites have both secretory and anti-absorptive effects increasing intestinal motility
    • Glycerin supp causes local rectal stimulation thus inducing defecation
  • Work within hours but may cause abdominal cramps
  • Long-term oral use of stimulant laxatives should be avoided
  • Short-term use of senna is considered safe during pregnancy and no increased risk of congenital abnormalities was observed with its use during pregnancy


  • Distend the colon thus inducing stool evacuation
  • Aid in the treatment of fecal impaction
    • Cleansing enema or short-term stimulant laxative can be used to relieve symptoms
    • Bulk-producing or osmotic laxative may then be used to maintain bowel patency


  • Stool softener eg Docusate sodium
  • Lubricant eg Mineral oil
  • Probiotics, in a systematic review, was shown to improve stool consistency and increase stool frequency in patients with chronic constipation

New Agents for Constipation

Peripheral Opioid Receptor Antagonists

  • Eg Methylnaltrexone, Naloxegol
  • Inhibit decreased gastrointestinal motility and delayed gastrointestinal transit time caused by opioids thereby reducing opioid-induced constipation
  • Given to patients with constipation as complication of advanced disease following opioid use


  • Eg Lubiprostone, Linaclotide
  • Stimulate chloride and fluid secretion into the intestinal lumen accelerating small bowel and colon transit
  • These agents have no arrhythmic effects

Serotonin 5-HT4 Receptor Agonist

  • Eg Prucalopride
  • Accelerates colonic transit time
  • Has demonstrated no adverse cardiac side effects in large trials
    • May be given to elderly patients and those with stable cardiovascular disease
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