DRUGS FOR CONSTIPATION
LAXATIVES
• Aperients, Purgatives, Cathartics
• These are drugs that promote evacuation of bowels.
• According to the intensity of action:
(a) Laxative or aperient:: milder action, elimination of soft but formed stools.
(b) Purgative or cathartic: stronger action resulting in more fluid and forceful evacuation.
MECHANISM OF ACTION
All purgatives increase the water content of the faeces by:
(a) A hydrophilic or osmotic action, retaining water and electrolytes in the intestinal lumen
lumen- increase
volume off colonic content and make it easily propelled.
(b) Acting on intestinal mucosa, decrease net absorption of water and electrolyte; intestinal transit is
enhanced indirectly by the fluid bulk.
(c) Increasing propulsive activity as primary action
action- allowing less time
me for absorption of salt and
water as a secondary effect.
Karthika D P
M.Pharm Pharmacology
, BULK PURGATIVES
Dietary fibre: bran
• Dietary fibre consists of unabsorbable cell wall and other constituents of vegetable food-
cellulose, lignins, gums, pectins, glycoproteins and other polysaccharides.
• Bran is the residual product of flour industry which consists of ~40% dietary fibre.
• It absorbs water in the intestines, swells, increases water content of faeces- softens it and
facilitates colonic transit.
• Dietary fibre supports bacterial growth in colon which contribute to the faecal mass.
• Increased intake of dietary fibres is the most appropriate method for prevention of functional
constipation.
• It is the first line approach for most patients of simple constipation.
• Drawbacks: Bran is generally safe, but it is unpalatable, large quantity needs to be ingested (20-
40 g/day) .
• Not be used in patients with gut ulcerations, irritable bowel syndrome (IBS) may be worsened
Psyllium (Plantago) and lspaghula
• They contain natural colloidal mucilage which forms a bulky gelatinous mass by absorbing water.
• It is largely fermented in colon: increases bacterial mass and softens the faeces.
• Prolonged intake of ispaghula and other soluble fibres reduces rectosigmoid intraluminal pressure
and helps to relieve symptoms of IBS, including pain, constipation as well as diarrhoea.
Methylcellulose
• 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.
STOOL SOFTENER
Docusates (Dioctyl sodium sulfosuccinate: DOSS)
• It is an anionic detergent, softens the stools by net water accumulation in the lumen by an action
on the intestinal mucosa.
• It emulsifies the colonic contents and increases penetration of water into the faeces.
• It is a mild laxative.
• Cramps and abdominal pain can occur. It is bitter; liquid preparations may cause nausea.
Hepatotoxicity is feared on prolonged use.
Karthika D P
M.Pharm Pharmacology
LAXATIVES
• Aperients, Purgatives, Cathartics
• These are drugs that promote evacuation of bowels.
• According to the intensity of action:
(a) Laxative or aperient:: milder action, elimination of soft but formed stools.
(b) Purgative or cathartic: stronger action resulting in more fluid and forceful evacuation.
MECHANISM OF ACTION
All purgatives increase the water content of the faeces by:
(a) A hydrophilic or osmotic action, retaining water and electrolytes in the intestinal lumen
lumen- increase
volume off colonic content and make it easily propelled.
(b) Acting on intestinal mucosa, decrease net absorption of water and electrolyte; intestinal transit is
enhanced indirectly by the fluid bulk.
(c) Increasing propulsive activity as primary action
action- allowing less time
me for absorption of salt and
water as a secondary effect.
Karthika D P
M.Pharm Pharmacology
, BULK PURGATIVES
Dietary fibre: bran
• Dietary fibre consists of unabsorbable cell wall and other constituents of vegetable food-
cellulose, lignins, gums, pectins, glycoproteins and other polysaccharides.
• Bran is the residual product of flour industry which consists of ~40% dietary fibre.
• It absorbs water in the intestines, swells, increases water content of faeces- softens it and
facilitates colonic transit.
• Dietary fibre supports bacterial growth in colon which contribute to the faecal mass.
• Increased intake of dietary fibres is the most appropriate method for prevention of functional
constipation.
• It is the first line approach for most patients of simple constipation.
• Drawbacks: Bran is generally safe, but it is unpalatable, large quantity needs to be ingested (20-
40 g/day) .
• Not be used in patients with gut ulcerations, irritable bowel syndrome (IBS) may be worsened
Psyllium (Plantago) and lspaghula
• They contain natural colloidal mucilage which forms a bulky gelatinous mass by absorbing water.
• It is largely fermented in colon: increases bacterial mass and softens the faeces.
• Prolonged intake of ispaghula and other soluble fibres reduces rectosigmoid intraluminal pressure
and helps to relieve symptoms of IBS, including pain, constipation as well as diarrhoea.
Methylcellulose
• 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.
STOOL SOFTENER
Docusates (Dioctyl sodium sulfosuccinate: DOSS)
• It is an anionic detergent, softens the stools by net water accumulation in the lumen by an action
on the intestinal mucosa.
• It emulsifies the colonic contents and increases penetration of water into the faeces.
• It is a mild laxative.
• Cramps and abdominal pain can occur. It is bitter; liquid preparations may cause nausea.
Hepatotoxicity is feared on prolonged use.
Karthika D P
M.Pharm Pharmacology
