Laxative Drugs
Laxatives are medications used to promote bowel movements and relieve constipation. They work by increasing the frequency or ease of stool passage.
Classification/Examples
- 1. Osmotic Laxatives:
- Lactulose
- Magnesium sulfate
- Magnesium hydroxide
- 2. Contact Laxatives:
- Bisacodyl
- Sodium picosulfate
- Castor oil
- 3. Bulk-forming Laxatives:
- Psyllium
- Methylcellulose
- 4. Stool Softeners:
- Docusate sodium
- Docusate calcium
Pharmacodynamics
- Osmotic Laxatives:
- Create an osmotic gradient in the colon, drawing water into the lumen and increasing intraluminal pressure, which stimulates bowel motility.
- Contact Laxatives:
- Directly stimulate nerve endings in the intestinal mucosa. They inhibit Sodium and Potassium ATPase, increasing adenyl cyclase activity and promoting bowel movement.
- Bulk-forming Laxatives:
- Increase fecal mass and stimulate peristalsis by promoting water retention in the stool, leading to improved bowel movements.
- Stool Softeners:
- Facilitate the incorporation of water and fat into the stool, softening it and easing its passage through the intestines.
Side Effects
- Common:
- Abdominal cramping, discomfort, diarrhea, nausea or vomiting, dehydration, electrolyte imbalances (such as low potassium or magnesium levels), excessive gas or bloating, rectal irritation or discomfort, and changes in bowel habits (including diarrhea or constipation).
- Rare/Severe:
- Dependence or habituation with long-term use, allergic reactions (rash, itching), severe allergic reactions (including anaphylaxis), rectal bleeding, hemorrhoids, kidney damage (with certain osmotic laxatives), and electrolyte disturbances.