Laxative/Purgative

Definition-
Laxatives (or purgatives) are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation.

Basic Concept-
1. Laxatives work to hasten the elimination of undigested remains of food in the large intestine and colon.
2. In many casses of intermittent constipation, it is best prevented by high fiber diet, adequate fluid intake, regular exercise and the heeding of nature's call.
3. If the above failed to do so, medical treatment can be an option.

Group of Laxatives

1. Bulk forming laxatives. Preparation include plant product- psyllium, methylcellulose, and synthetic fiber- polycarbophil.

Mode of action(MOA)- ( indigestible, hydrophilic colloids that) Absorb water, forming a bulky, emmolient gel that distend the colon and promote peristalsis.

2. Stool Surfactant Agents/ Softners. Preparation include Docusate ( oral, rectal ), glycerin suppository, and mineral oil

MOA- Agents soften stool materia, permitting water and lipid to penetrate.

Route of administration(ROA)- oral, rectal

Side effects(SE)- Long term ak Chronic use can impair absorpton of fat soluble vitamins-A,D,E,K

Contraindication(CI)- Severe Lipid Pneumonitis, can cause aspiration.

3. Osmotic Laxativeves
Concept- Increase in stool liqidity due to obligate increase in fecal fluid.

a.Non-absorbable Sugar or Salt
Preparation include Magnesium oxide aka milk of magnesia (commonly used), Sorbitol and Lactulose.

Most commonly used of Purgatives ( Agents that prompt bowel evacuation ) is magnesium citrate and sodium phosphate ( hyperosmolar agents)

MOA-
Sorbitol and lactulose are metabolized by the colonic bacteria, producing severe flatus and cramps
Hyperosmollar agents induce rapid movement of water into the distal small bowel and colon leads to a high volume of liquid stool followed by rapid relief of constipation

AE-
Cramps- Sorbitol and Lactulose
Intravascular volume depletion and electrolyte fluctuations- Hyperosmollar agent

CI-
Patient with hypermagnesemia-Milk of magnesia
Patient who are frail, elderly renal defect and significant cardiac disease-Hyperosmollar agents

b. Balanced Polyethylene Glycol(PEG)
Used for complete cleansing prior to GIT endoscopic procedures.

MOA- Balanced the isotonic solutions in the bowel. Solution are designed so that no significant shift of intravascular fluid or electrolyte occur. Hence it is safe for all patient.
No significant cramps or flatus reported.

4. Stimulant Laxatives

a. Anthraquinone derivatives. Prepation include aloe, senna and cascara-ocur naturally in plant.
Chronic use leads to Melanosis Coli- brown pigmentatio of colon.

b. Diphenylmethane derivatives.
Preparation include Phenolphthalein.
SE- Cardiac toxicity. Removed from the market

c. Castor Oil
MOA- It is hydrolyzed in upper intestine to ricinoleic acid, a local irritant that stimulates intestinal motility.

5. Serotonin 5-HT4 Receptor Agonist
Preparation include Tegaserod- Serotonin 5HT4 partial agonist.



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