Constipation

Question 1

Bulk-forming laxatives – Examples, onset, MoA, side fx, counselling pts

Answer 1

Examples

• Ispaghula husk
• Methyl cellulose
• Sterculia

Onset
- 2-3 days

MoA
- Increasing mass of faeces to stimulate peristalsis

Common side fx
- Flatulence and abdominal distension

Counselling

• Adequate hydration to prevent intestinal obstruction
• Do not take before bed time

Question 2

Stimulant laxatives – Examples, onset, MoA, side fx, counselling pts

Answer 2

Examples

• Bisacodyl
• Docusate sodium
• Glycerol
• Senna
• Sodium picosulfate

Onset
- 6-12 hours suppositories 15-60 mins

MoA

• Direct intestinal motility stimulation via colonic nerves
• Docusate sodium has stimulant and stool softener properties
• Glycerol acts as a rectal stimulant

Side fx
- Abdominal pain

Counselling
- Take at bedtime for an effect the next morning

Question 3

Faecal softener laxatives – Examples, onset, MoA, side fx, counselling pts

Answer 3

Examples

• Liquid paraffin (not recommended) some evidence to suggest granuloma formation
• Docusate sodium

Onset
- 1-2 days

MoA
- Docusate: surface tension of stool is reduced to allow water to pass through and soften the structure + mild stimulant activity

Side fx

• Liquid paraffin: anal seepage & irritation, granulomatous reactions via absorption of the drug, lipoid pneumonia and malabsorption of fat-soluble vitamins
• Docusate: Abdominal pain (rare)

Counselling
- Adequate hydration (and nourishment)

Question 4

Osmotic laxatives – Examples, onset, MoA, side fx, counselling pts

Answer 4

Examples

• Lactulose
• Macrogols
• Magnesium salts

Onset

• 1-3 days
• Magnesium salts: few hours

MoA
- Fluid retained in the bowel via osmosis/altering of the fluid distribution in the faeces

Side fx

• Flatulence
• Bloating
• Abdominal cramps

Counselling
- Adequate hydration