LAXATIVES
LAXATIVES
- Used for preventing constipation, by promoting evacuation of bowels.
- Also referred to as “Aperients, Purgatives, Cathartics”.
Other best measures:
- High fiber diet, adequate fluid intake & regular exercise.
- Unresponsive patients require laxatives.
Classification of laxative drugs:
| Luminal active agents | Stimulant purgative | Prokinetics | New agents |
Subdivided into
1. Bulk-forming agents:
2. Surfactant (Stool softner):
3. Osmotic: Subdivided into: Saline laxatives & non-digestive sugars & alcohols.
|
1. Diphenylmethanes:
2. Anthraquinones:
3. Castro oil. |
1. 5HT4 agonists:
2. D2 antagonists:
This section is a separate module.
|
1. Chloride secretory agents:
2. Opioid receptor antagonists (For opioid-induced constipation):
|
Important drugs:
1. Chloride secretory agents:
- Drugs: Lubiprostone & Linaclotide.
- MOA:
- Stimulate Cl– channel opening in intestine.
- Increase liquid secretion in gut.
- Decrease transit time.
- Used for chronic constipation.
- Linaclotide:
- Guanylate cyclase agonist.
- Indicated for oral treatment of idiopathic constipation & IBS with constipation.
2. Non-digestive sugars & alcohols:
- Lactulose:
- MOA:
- Acts by conversion to short chain fatty acids in colon.
- Fatty acids –> result in decreased intestinal juice pH.
- At low pH, ammonia becomes ionized (NH4+) & cannot be absorbed.
Contraindications:
- In presence of megacolon – Bulk-forming agents.
- In chronic renal failure – Saline purgatives.
- In presence of intestinal obstruction – Stimulant purgatives.
Adverse effects:
- Melanosis coli (brown pigmentation of colon) – Chronic use of anthraquinone derivatives (senna & cascara).
- Risk of potential carcinogenicity – Phenolphthalein.
- Deficiency of fat-oluble vitamins – Liquid paraffin.
- Hypokalemia & causes constipation itself – Associated with laxative abuse.
Laxative/purgative abuse:
- Obsession for regular purgative usage.
- Maybe reflection of psychological problem.
Effects of purgative abuse:
- Constipation itself.
- Flaring of intestinal pathology (rupture of inflamed appendix).
- Fluid & electrolyte imbalance (especially hypokalaemia).
- Steatorrhoea
- Malabsorption syndrome.
- Protein-losing enteropathy.
- Spastic colitis.
Exam Important
- Laxatives used for preventing constipation, by promoting evacuation of bowels.
- Laxatives also referred to as “Aperients, Purgatives, Cathartics”.
- Senna & Cascara are including under stimulant purgative & are used as laxatives.
- Opioid receptor antagonists like Methylnaltrexone & Alvimopan are useful for opioid-induced constipation.
- Docusate (DOSS), liquid paraffin & mineral oil are all stool softner/surfactant.
- Lubiprostone & Linaclotide are chloride secretory agents.
- Luminal active agents useful as laxatives are further subdivided into bulk-forming, surfactant & osmotic agents.
- Phenolphthalein is a stimulant purgative.
- Lubiprostone & Linaclotide stimulates Cl– channel opening in intestine, increases liquid secretion in gut & decreases transit time, hence useful in chronic constipation.
- Linaclotide is a guanylate cyclase agonist, indicated for oral treatment of idiopathic constipation & IBS with constipation.
- Chronic use of anthraquinone derivatives (senna & cascara) causes Melanosis coli (brown pigmentation of colon).
- Phenolphthalein shows risk of potential carcinogenicity.
- Liquid paraffin result in deficiency of fat-soluble vitamins.
- Laxative/purgative abuse is assocaited with hypokalemia & causes constipation itself.
- Effects of laxative/purgative abuse include steatorrhoea, malabsorption syndrome, protein-losing enteropathy & spastic colitis.
Don’t Forget to Solve all the previous Year Question asked on LAXATIVES
