Laxatives (aperients, Purgatives, Cathartics): These are drugs that promote evacuation of bowel. A distinction is sometimes made according to the intensity of action.
- Laxative or aperient: milder action, elimination of soft but formed stools.
- Purgative or cathartic: stronger action resulting in more fluid evacuation.
Many drugs in low doses act as laxative and in larger doses as purgative.
- Bulk forming
Dietary fibre: Bran, Psyllium (Plantago), Ispaghula, Methylcellulose
- Stool softener
- Stimulant purgatives
Fixed oil: Castor Oil
- Osmotic purgatives
Magnesium salts: sulfate, hydroxide
Sodium salts: sulfate, phosphate
All purgatives increase the water content of the faeces by:
- A hydrophilic or osmotic action, retaining water and electrolytes in the intestinal lumen-increase volume of colonic content and make it easily propelled.
- Acting on intestinal mucosa, decrease net absorption of water and electrolyte; intestinal transit is enhanced indirectly by the fluid bulk.
- Increasing propulsive activity as primary action-allowing less time for absorption of salt and water as well as a secondary effect.
Common Medicine for Constipation and Diarrhea:
A semi-synthetic, colloidal, hydrophilic derivative of cellulose that remains largely unfermented in colon. A dose of 4-6 g/day is satisfactory in most individuals.
Generous amounts of water must be taken with all bulk forming agents. The choice among different bulking agents is a matter of personal preferences.
It is a viscous liquid; a mixture of petroleum hydrocarbons, that was introduced as a laxative at the turn of 19th century.
Millions of gallons have passed through the intestinal pipeline since then. It is pharmacologically inert. Take for 2-3 days, it softens stools and is said to lubricate hard scybali by coating them
Dose: 15-30 ml/day-oil as such or in emulsified form.
They are partly absorbed and re-excreted in bile. The enterohepatic circulation is greater in case of phenolphthalein which can produce protracted action.
Bisacodyl is activated in the intestine by deacetylation. The primary site of action of diphenyl methanes is in the colon where they irritate the mucosa, produce mild inflammation and increase secretion. One or two semi-formed motions occur after 6-8 hours. Optimum doses vary considerably among individuals.
It is one of the oldest purgatives. Castor oil is bland vegetable oil obtained from the seeds of Ricinus communis. It mainly contained triglyceride of ricinoleic acid which is a polar long-chain fatty acid.
Castor oil is hydrolyzed in the ileum by lipase to ricinoleic acid and glycerol. Ricinoleic acid, being polar, is poorly absorbed. It was believed to irritate the mucosa and stimulate intestinal contractions. The primary action is now shown to be decreased intestinal absorption of water and electrolytes, and enhanced secretion by a detergent like action on the mucosa.
Due to unpalatability, frequent cramping, a rather violent action, possibility of dehydration and after-constipation (Due to complete evacuation of colon), it is no longer a favored purgative. Regular use is particularly to be avoided-may damage intestinal mucosa.
It is a semisynthetic disaccharide of fructose and lactose which is neither digested nor absorbed in the small intestine-retains water.
Further, it is broken down in the colon by bacteria to osmotically more active products. In a dose of 10 g BD taken with plenty of water, it produces soft formed stools in 1-3 day.
Flatulence and flatus are common, cramps occur in few. Some patients feel nauseated by its peculiar sweet taste.
Choice and Use of Purgatives:
Laxatives are as important for their harmfulness as they are for their value in medicine.
All laxatives are contraindicated in:
- A patient of undiagnosed abdominal pain, colic or vomiting.
- Organic(secondary) constipation due to stricture or obstruction in bowel, hypothyroidism, hypercalcemia, malignancies and certain drugs, e.g.-opiates, sedatives, anticholinergics including antiparkinsonian, antidepressants and antihistaminic, oral iron, clonidine, verapamil and laxative abuse itself.
Treatment of Diarrheas:
Diarrhea is too frequent, often too precipitate passage of poorly formed stools. It is defined by WHO as 3 or more loose or watery stools in a 24-hour period.
In pathological terms, it occurs due to passage of excess water in faeces. This may be due to:
- Decrease electrolyte and water absorption.
- Increased secretion by intestinal mucosa.
- Increased luminal osmotic load.
- Inflammation of mucosa and exudation into lumen.
- About 88% of diarrhea-associated deaths are attributable to unsafe water, inadequate sanitation, and insufficient hygiene.
- Rotavirus is the leading cause about 40% of hospitalizations for diarrhea in children under 5.
- Most diarrheal germs are spread from the stool of one person to the mouth of another. These germs are usually spread through contaminated water, food, or objects.
Diarrhea diseases constitute a major cause of morbidity and mortality worldwide; especially in developing countries.
Recurrent or protracted diarrhea is also a major cause of protein-calorie malnutrition in developing countries. Even mild diarrhea, and that in adults, is a disabling symptom and an inconvenience.
It is more prevalent among children. The global burden of pediatric diarrhea is estimated to be 2.5 billion episodes with 2.5-3.5 million deaths under 5 years of age per year.
Diarrhea is responsible for the death of more than 90% of under 5 children in low and lower-middle income countries. Regionally, South Asia and sub-Saharan Africa accounted for 88% of the deaths with the same age group.