Laxatives
Laxatives are milder in action and deal with evacuation of rectum. With use of laxatives, there is elimination of formed stools.
Cathartics
Cathartics are severe in action and deal with evacuation of colon. With their use, liquid form of stool is eliminated.
Purgatives
In between the two.
Functions Of Colon
- Modification of consistency
Maintenance of consistency of stool through reabsorption of water. More water is reabsorbed, stool will harder.
- Storage of fecal material
- Evacuation takes place only when it is convenient for person.
Factors affecting function of colon
1. Diet
Diet rich in fiber content will produce a softer consistency of stool
2. Water intake
Also plays important role
What is constipation ?
Different in different parts of world. It is based on culture as well e.g. in west, passing 2 stool/week is no constipation, but in the east, passing 1 stool in one day is constipation.
If person is straining hard and consistency of stool is also hard, it is constipation and usually is said that 2 stools /week are constipation.
Causes
- Diet
Diet lacking fiber content will lead to constipation
- Structural abnormalities
Hemorrhoids and anal fissure. In these, patient is reluctant to pass stool.
- Tumors of colon can cause constipation
- Intestinal obstruction
- Drugs
a. Opioids
b. Anticholinergics
c. TCAs
d. Calcium channel blockers
- Systemic diseases
- Hypothyroidism
- Diabetes mellitus
- Parkinsonism
- Idiopathic
Management of constipation
- To remove the cause
- Diet changes
- Use of drugs –mostly wrongly described.
Purgatives
Bulk Purgatives
Hydrophilic colloids
- Ispaghula Husk
- Bran
- Methylcellulose
- Psyllium seed
Stimulant Purgatives
Anthraquinone derivatives
- Senna
- Cascara
- Aloe
Diphyenyl methane derivatives
- Bisacodyl
- Phenolphthalein –withdrawn due to cardiotoxicity
Castor oil
Osmotic Laxatives
Saline Purgatives
- Magnesium sulfate
- Magnesium Hydroxide
- Sodium Phosphate
Non-absorbable Sugars
- Lactulose
- Sorbitol
Alcohol
- Glycerin
Stool Softeners
- Sodium docusate,
- Calcium docusate,
- Potassium docusate
- Mineral Oil
5 HT4 Receptor Agonist
Tegaserod
Bulk Forming Purgatives
Mechanism of Action
Fiber in our diet is:
A. Partly fermented
B. Unfermented
Fermented portion is converted into short chain fatty acids which have got prokinetic activity (they increase motility and secretion)
Unfermented portion imbibes water and increases bulk of stool due to this there is distention and increase in peristalsis.
Side Effects
- Abdominal discomfort
- Allergic reaction (with psyllium seeds)
Uses
- Mainly constipation
- Irritable bowel syndrome
- Diverticulosis
- When staining of stool is to be avoided
Stimulant Purgatives
Powerful purgatives
Anthraquinone Purgatives
Mechanism of Action
Contain active principle EMODIN which is a glycoside. It is passed into colon where it is acted upon by bacteria and they liberate ANTHROL which has prokinetic activity
Take a few hours (5-6 hours) to produce their actions.
Side Effects
1. Melanosis coli
Harmless pigmentation of colonic mucosa. It may be due to use of these drugs or due to pigment rich bacteria.
2. Cathartic colon
when used for long period of time, abnormal dilation of colon occurs and haustrations are lost. Damage to muscularis mucosae and neurons of myenteric plexus takes place.
These two adverse effects are reversible in some persons.
Diphenylyl methane Derivatives
Bisacodyl
Mechanism of Action
Hydrolysed in gut through deacetylation and converted to active form which produces low grade inflammation as a result of which motility and secretions are increased.
Take 5-6 hours for action to occur.
Indications
- Constipation
- Prepration of bowel for Radiographic Studies
Side Effects
- Abdominal pain/discomfort
- Few allergic reactions (rarely Steven’s Johnsons syndrome)
Castor Oil
Oldest purgative largely used by quacks.
02 components
a. Triglyceride – Glycerol & Ricinoleic acid
b. Proteins
Triglyceride component is acted upon by pancreatic lipases as result of which glycerol and ricinoleic acid is formed. Ricinoleic acid has prokinetic activity.
Prolonged use is prohibited, it can damage intestinal mucosa as well as intestinal neurons.
Fecal Softeners
Docusate
Softens stool
Cause accumulation of water in the lumen of colon because of which they soften the stool.
Motility of gut
Increased by stimulating cAMP
Emulsifies colonic contents by increasing the penetration of water into stool.
Disrupts mucosal barrier
Interfere with absorption of fat soluble vitamins (A, E and K)
Can interfere with absorption of different drugs
Side Effects
Mainly GIT
Abdominal Cramps, Pain, Nausea, Bitter In Taste
Hepatotoxicity has been feared on prolonged use
Liquid Paraffin
A viscous mixture of petroleum hydrocarbons with a lubricant action
Introduced as laxative at start of 19th century and largely used then.
Taken for about 2-3 days.
Use
Helps in relieving constipation as it coats the stool.
Side Effects
Unpleasant to swallow
Interference with absorption of fat soluble vitamin
Osmotic Purgatives
Not absorbed in small intestine & retain water due to osmolar action
By absorbing water, increase the bulk of stool because of which there is distention of colon and increase in motility
Magnesium salts can increase secretion of CCK, which aids in purgative action of Mg.
Uses
- Preparation of bowel before surgery
- Preparation of bowel before colonoscopy
- In food and drug poisoning
- Glycerine
Given in form of suppository. Acts in 02 ways
- Osmotic action
- Lubricant action
- Lactulose
Neither digested nor absorbed. Converted into organic acid, decrease pH of colon, converts ammonium into non-absorbable ammonium ion and thus decreases ammonia absorption.
Uses
Hepatic encephalopathy
Contraindications
Mg salts in renal diseases
Na salts in congestive heart failure and patients suffering from Na retaining conditions
Prolonged use
Electrolyte and fluid imbalance.
Side Effects
- Renal and cardiac disease
- Abdominal distension
- Flatulence
Tegaserod
Partial agonist at serotonin 4 receptors and has high affinity for these receptors as compared with 5HT3 receptors.
Resembles serotonin and increases release of Acetylcholine and calcitonin Gene Related Peptides by acting on pre-junctional serotonin 4 receptors.
Increases cAMP dependent chloride efflux thus increases secretion, motility
Prokinetic activity is seen in stomach and small/large intestine.
Uses
- In chronic constipation when all other remedies fail.
- Gastropharesis
- Irritable bowel syndrome
Adverse Effects
- Diarrhea
- Abdominal discomfort
- Flatulence
- Headache
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