Constipation: It is a condition where there is infrequent bowel movement.
Causes: Diet( lack of fibers and liquids),
- lack of exercise,
- irregular bowl habits,
- drugs induced,
- disease state
Sign and Symptoms: Infrequent defecation,
- rectal bleeding,
- weight loss in chronic constipation.
Treatment: Drugs that promote evacuations of bowel.
A. Laxatives: Elimination of soft but formed stools. They are generally used to relieve constipation. It has mild action
B. Purgatives: It has stronger action, resulting in more fluid evacuation.
Mechanism of action of Laxatives:
- Inhibiting Na+K+ATPase of villous cells, impairing electrolyte and water imbalance.
- Stimulating adenylyl cyclase in crypt cells, increasing water and electrolyte secretion.
- Enhancing PG synthesis in mucosa which increase secretion.
- Increasing NO synthesis which enhances secretion and inhibits non-propulsive contractions in colon
- Structural injury to the absorbing intestinal mucosal cells.
Classification of laxatives:
A. Bulk forming agents:
Dietary fibre: Bran, psyllium, Ispaghula, Methyl cellulose.
B. Stool softener:
Docusates (DOSS), Liquid paraffin
C. Osmotic purgatives:
Mag. sulfate, mag. hydroxide, sod. sulfate, sod. phosphate, sod. pot. tartrate, lactulose, lactitol.
D. Stimulant purgative:
Bisacodyl, Sod. picosulfate
Senna, Cascara sagrada
A. Bulk forming agents: These are indigestible, hydrophilic colloids that absorb water, forming a bulky, emollient gel that distends the colon and promotes peristalsis.
Uses: Improve stool consistency and frequency with regular use.
Side effects: Bloating, flatulence and distension.
B. Stool softener:
1. Docusates: It is an anionic detergent, softens the stool, by net water accumulation in the lumen by an action on the intestinal mucosa.
2. Liquid paraffin: It is viscous liquid mixture of petroleum hydrocarbons that is pharmacologically inert.
Uses: May be useful with anal fissures of haemorrhoids. Liquid paraffin is not recommended for treatment of constipation.
Side effects: Long term use may result in depletion of Vit A, D, E, K. Risk of aspiration and lipid pneumonia.
C. Osmotic laxatives: Osmotic laxatives are soluble but non absorbable compounds that result in increased stool liquidity due to increase in fecal fluid. lactulose is a semisynthetic disaccharide of lactose and fructose 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.
Uses: Saline laxatives such as mag. hydroxide, mag. sulfate, poorly absorbed sugars such as lactulose, may be used for the treatment of acute constipation, or the prevention of chronic constipation. Magnesium oxide (milk of magnesia) is a commonly used osmotic laxative. It should not be used for prolonged periods in patients with renal insufficiency due to risk of hypermagnesemia. lactulose used in hepatic encephalopathy, distal ulcerative colitis.
D. Stimulant purgatives:
a. Bisacodyl: It is absorbed in the intestine and excreted in bile to undergo partial enterohepatic circulation . After activation in the intestine by deacetylation it irritates colonic mucosa to increase fluid secretion.
Side effects: Stevens-Johnson syndrome, skin rashes and fixed drug eruption.
b. Sodium picosulfate: It is converted in to active form by colonic bacteria through hydrolysis. Which then acts locally to irritate the mucosa and activate myenteric neurons.
Uses: It is sued in colonic surgery and to evacuate the colon for colonoscopy.
Senna and cascara sagrada: Senna is most popularly used. Unabsorbed in the small intestine, they are passed to the colon where bacteria liberate the active anthrol form, which either acts locally or is absorbed in to circulation- excreted in bile to act on small intestine. The active principle stimulates the myenteric plexus to increase peristalsis and promote secretion and inhibit salt and water absorption in the colon.
Side effects: Skin rashes, fixed drug eruption are the occasional adverse effects.
3. 5-HT4 agonists:
Prucalopride: It is selective 5-HT4 agonist. It activates prejunctional 5-HT4 receptors on intrinsic enteric neurons to enhance release of the excitatory transmitters ACh, promoting propulsive contractions in ileum and more prominently in colon.
Uses: Colonic transit and stool frequency improved in constipation-predominent IBS(inflammatory bowel syndrome).
Side effects: Dizziness, headache, fatigue, abdominal pain and diarrohea.
4. PG analogue:
Lubiprostone: It is an EP4 receptor agonist which activates mucosal cl channel by stimulating guanylyl-cyclase C. It produces cl rich intestinal fluid and accelerates colonic transit.
Uses: It is used in constipation- prominent IBS, and in idiopathic chronic constipation.
1. What is infrequent bowel movement?
2. What are the causes of constipation?
a. Lack of exercises
b. Lack of fibers and liquids
c. Disease state
d. All of these.
3. What are the sign and symptoms of constipation?
a. Infrequent defecation
c. Weight loss due to chronic constipation
d. All of these
4. Elimination of soft but formed stools.
5. It has stronger action, resulting in more fluid evacuation.
6. Which type of laxative is DOSS?
a. Bulk forming agents
b. Osmotic purgatives
c. Stool softener
d. Stimulant purgatives
7. Which is 5-HT4 agonist?
a. Liquid paraffin
c. Mag. hydroxide
8. Which drug caused “Steven-Johnson syndrome”?
d. Liquid paraffin
9. Which drug is used in colonoscopy?
a. Liquid paraffin
b. Sodium picosulfate
d. Mag. sulfate
10. Which drugs are used in constipation-predominent IBS(inflammatory bowel syndrome)?
c. a & b
11. What are the side effects of bulk forming agents?
d. All of these
12. Which drug is EP4 receptor agonist?
c. Liquid paraffin
13. What is osmotic laxative?
a. Mag. hydroxide
b. Liquid paraffin
14. Senna and cascara sagrada are:
b. PG analogue
15. Mech of action of laxatives.
a. Inhibiting Na+K+ATPase of villous cells, impairing electrolyte and water imbalance.
b. Stimulating adenylyl cyclase in crypt cells, increasing water and electrolyte secretion.
c. Enhancing PG synthesis in mucosa which increase secretion.
d. All of above.
- “K.D Tripathi”, Drugs for constipation, page no- 721-726, 8th edition, june2018.
- ” Dr. Inderjeet Banerjee”, Health and medicine 13july 2017.