Laxatives
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laxatives AND constipation
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NICE constipation laxatives adult management guideline
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https://cks.nice.org.uk/topics/constipation/management
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Laxatives
Laxatives are drugs that facilitate defecation and relieve constipation. Start with adequate dietary fibre, fluids, exercise, and responding to the urge to defecate. Persistent constipation should be assessed for causes such as medication effects, endocrine/metabolic disease, or bowel obstruction. Katzung's Basic and Clinical Pharmacology, 16th ed., p. 1709.
| Class | Examples | Main action | Common use / cautions |
|---|---|---|---|
| Bulk-forming | Psyllium, methylcellulose, calcium polycarbophil | Absorb water, increase stool bulk, and stimulate peristalsis | Often suitable for long-term use. Take with plenty of water. Can cause bloating and flatulence; avoid if bowel obstruction or inadequate fluid intake is possible. |
| Stool softeners / surfactants | Docusate, glycerin suppository | Allow water and lipids to penetrate stool | Useful when straining should be minimized. Limited effect for established chronic constipation. |
| Lubricant | Mineral oil | Coats stool and reduces water absorption | Avoid routine or prolonged use. Aspiration can cause lipoid pneumonia; may reduce absorption of vitamins A, D, E, and K. |
| Osmotic | Polyethylene glycol (PEG/macrogol), lactulose, sorbitol, magnesium hydroxide, magnesium citrate | Retain water in the bowel, softening stool | PEG is commonly effective and causes less gas than lactulose. Lactulose may cause cramps and flatulence. Avoid prolonged magnesium products in renal impairment because of hypermagnesemia. |
| Stimulant | Senna, bisacodyl, sodium picosulfate | Stimulate enteric nerves and increase colonic fluid/electrolyte secretion | Helpful for short-term rescue or if osmotic agents are insufficient. May cause abdominal cramps and diarrhea. |
| Secretagogues | Lubiprostone, linaclotide, plecanatide | Increase intestinal chloride and water secretion | Prescription options for chronic idiopathic constipation or constipation-predominant IBS when simple measures fail. |
| Peripheral opioid antagonists | Naloxegol, naldemedine, methylnaltrexone | Block gut μ-opioid receptors without substantially reversing analgesia | For opioid-induced constipation after inadequate response to usual laxatives. |
Practical approach
- Hard, infrequent stool: consider fibre if hydration is good, or an osmotic laxative such as PEG.
- Persistent difficulty despite osmotic treatment: add a short course of stimulant laxative.
- Opioid-related constipation: a stimulant plus an osmotic agent is often used; consider a peripheral opioid antagonist if this is ineffective.
- Faecal impaction or suspected obstruction: do not simply self-treat with repeated laxatives. Seek clinical assessment.
Important safety points
Seek urgent medical care for constipation with severe or worsening abdominal pain, vomiting, marked abdominal distension, inability to pass gas, rectal bleeding or black stool, fever, unexplained weight loss, or new constipation in an older adult. Do not use laxatives if bowel obstruction is suspected.
PEG has strong evidence for improving stool frequency and consistency in chronic idiopathic constipation, while bisacodyl/sodium picosulfate are effective stimulant options. Sleisenger and Fordtran's Gastrointestinal and Liver Disease, p. 289. A recent systematic review also evaluated osmotic versus stimulant therapy in childhood constipation, so children need age-appropriate clinician or pharmacist advice rather than adult self-treatment (Cochrane review, PMID 42770374).
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