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Home > Pre-Reg Pharmacist > Over-the-counter (OTC) laxatives for constipation

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Over-the-counter (OTC) laxatives for constipation

Laxative Class Examples of Laxatives Onset of Action Mechanism of Action Common Adverse Effects / Side Effects Counselling Points
Bulk-forming laxatives Ispaghula husk, methylcellulose and sterculia 2-3 days Increase faecal mass which stimulates peristalsis Flatulence and abdominal distension Drink adequate amounts of fluid to avoid intestinal obstruction

Do not take before bedtime
Stimulant laxatives Bisacodyl, docusate sodium, glycerol, senna, and sodium picosulfate 6-12 hours

Suppositories 15-60 minutes
Increase intestinal motility by directly stimulating the colonic nerves

Docusate sodium acts both as a stimulant and as a softening agent

Glycerol acts as a rectal stimulant
Abdominal pain Take at bedtime to produce an effect the next morning
Faecal softeners Liquid paraffin (should not be recommended – see adverse / side effects) and docusate sodium 1-2 days Docusate sodium acts as a faecal softener by lowering the surface tension which allows fluid to penetrate the stool, thereby softening the stool. Docusate sodium also has mild stimulant action Liquid Paraffin: anal seepage and irritation, granulomatous reactions caused by absorption of small quantities of liquid paraffin, lipoid pneumonia, and malabsorption of fat-soluble vitamins  
Osmotic laxatives Lactulose, macrogols and magnesium salts 1-3 days

Magnesium salts – few hours
Retain fluid in the bowel by osmosis or alter the pattern of water distribution in the faeces Flatulence, bloating, abdominal cramps Drink adequate amounts of fluid


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