Laxatives

Laxatives are medications used to treat constipation by facilitating bowel movements. They work through various mechanisms and are categorised based on their action in the gastrointestinal (GI) tract.

1. Bulk-Forming Laxatives

  • Mechanism of Action:
    • Bulk-forming laxatives absorb water into the intestines, increasing stool bulk and stimulating peristalsis (the wave-like contractions of the intestinal muscles).
  • Medications:
    • Psyllium (Metamucil):
      • Uses/Considerations: Used for chronic constipation and to promote regular bowel movements. Requires adequate fluid intake to avoid intestinal blockage.
      • Side Effects: Bloating, gas, and risk of intestinal obstruction if not taken with sufficient water.
    • Methylcellulose (Citrucel):
      • Uses/Considerations: Similar to psyllium, it helps soften stools and promote bowel movements. Also requires adequate hydration.
      • Side Effects: Similar to psyllium, including bloating and gas.

2. Stool Softeners

  • Mechanism of Action:
    • Stool softeners, also known as emollient laxatives, increase the amount of water and fat absorbed into the stool, making it easier to pass.
  • Medications:
    • Docusate Sodium (Colace):
      • Uses/Considerations: Used to relieve occasional constipation and prevent straining during bowel movements, especially in patients with hemorrhoids or after surgery.
      • Side Effects: Stomach cramps and diarrhea.
    • Docusate Calcium (Surfak):
      • Uses/Considerations: Similar to docusate sodium, used for occasional constipation.
      • Side Effects: Stomach cramps and diarrhea.

3. Osmotic Laxatives

  • Mechanism of Action:
    • Osmotic laxatives draw water into the bowel from the surrounding tissues, increasing the water content and volume of the stool.
  • Medications:
    • Polyethylene Glycol (Miralax):
      • Uses/Considerations: Used for short-term treatment of constipation. Safe for use in most patients, including children and the elderly.
      • Side Effects: Bloating, gas, nausea, and cramping.
    • Lactulose:
      • Uses/Considerations: Used for chronic constipation and to reduce ammonia levels in patients with hepatic encephalopathy.
      • Side Effects: Bloating, gas, diarrhea, and abdominal discomfort.
    • Magnesium Hydroxide (Milk of Magnesia):
      • Uses/Considerations: Used for occasional constipation and as an antacid. Should be used with caution in patients with kidney disease.
      • Side Effects: Diarrhea, electrolyte imbalance, and dehydration.

4. Stimulant Laxatives

  • Mechanism of Action:
    • Stimulant laxatives increase the rhythmic muscle contractions of the intestines.
  • Medications:
    • Bisacodyl (Dulcolax):
      • Uses/Considerations: Used for short-term relief of constipation and for bowel preparation before medical procedures.
      • Side Effects: Abdominal cramping, diarrhea, and potential for dependence with long-term use.
    • Senna (Senokot):
      • Uses/Considerations: Derived from the senna plant, used for short-term relief of constipation.
      • Side Effects: Abdominal pain, cramping, diarrhea, and potential for dependence with prolonged use.

5. Lubricant Laxatives

  • Mechanism of Action:
    • Lubricant laxatives coat the stool and the bowel lining with a waterproof film, allowing the stool to retain its moisture and pass more easily.
  • Medications:
    • Mineral Oil:
      • Uses/Considerations: Used for short-term relief of constipation. Should not be used long-term due to risks of lipid pneumonia if aspirated.
      • Side Effects: Risk of lipid pneumonia, reduced absorption of fat-soluble vitamins (A, D, E, K), and potential for anal leakage.

Side Effects and Considerations

  • Hydration: Many laxatives require adequate fluid intake to be effective and to prevent complications like dehydration and intestinal blockage.
  • Long-term Use: Prolonged use of some laxatives, especially stimulant laxatives, can lead to dependence and decreased bowel function.
  • Electrolyte Imbalance: Osmotic and stimulant laxatives can cause electrolyte imbalances, particularly with long-term use.
  • Abdominal Discomfort: Common side effects include bloating, gas, cramps, and diarrhea.
  • Interactions: Some laxatives can interact with other medications, reducing their effectiveness or increasing the risk of side effects.