Concept About Purgatives, Laxatives – This book covers the entire syllabus of “Pharmacology” prescribed by BNMC- for diploma in nursing science & midwifery students. We tried to accommodate the latest information and topics. This book is an examination setup according to the teachers’ lectures and examination questions.
At the end of the book, previous questions are given. We hope in touch with the book students’ knowledge will be upgraded and flourish. The unique way of presentation may make your reading of the book a pleasurable experience.
Concept About Purgatives, Laxatives
Purgatives are the agents that promote defecation largely by reducing the viscosity of the contents of lower colon.
Laxatives;
Agents that evacuate soft, formed stool without griping and without much loss of water are called laxatives.
➤ Insulin
➤Steroid
Classification of Purgatives:
A. Bulk forming purgatives:
1. Hydrophilic colloid:
➤ Ispaghula husk
➤ Methyl-cellulose
➤ Sterculia
2. Indigestible vegetable:
➤ Agar
➤ Bran
B. Osmotic laxative:
➤ Saline purgatives
➤lactulose(disaccharide)
➤ MgSO4, MgCO
➤ Mg(OH):
➤ Na-citrate
➤ Na phosphate
C. Faecal softeners (lubricants):
➤ Liquid paraffin
➤Docusate sodium
➤ Mineral oil
D. Stimulant or irritant laxatives:
➤Anthraquinone group (aloes and aloin, senna)
➤Irritant oils (castor oil, croton oil)
Purgative resins (Jolap, cologynth)
Other compounds: Bisacodyl
E. Recently administered laxatives
1. Suppository:
➤ Bisacody
➤Docusate sodium
➤Glycerin
2. Enema:
➤Docusate sodium
➤Arachis oil
➤MgSO4
Criteria of an ideal purgative
a. Dependable and selective action on intestine.
b. Should not interfere digestion and absorption.
c. Should not produce colic and vomiting.
d. Should not produce tolerance and habituation.
e. Should not cause pelvic congestion (abortion)
f. Poorly absorbed and should not toxic and nonirritant
g. Should be cheap and available.
Indication of purgatives
a. Prevention and treatment of functional constipation.
b. In food or drug poisoning to finish the intestinal tract (saline purgatives).
c. Following antihistamine to eliminate the parasites (saline).
d. Before and after surgery (castor oil).
e. Prior to radiological examination of abdomen.
f. In patients with anal fissure, hernia, piles, typhoid fever and cardiac disease to avoid excessive straining during defecation (lubricant purgatives).
g. Prior to proctologic examination.
h. In hepatic coma and megacolon (MgSO4).
i. Along with oxytocin to initiate labour
Adverse effects of purgatives:
a. GIT disturbance: dyspepsia, anorexia, nausea.
b. Nutritional deficiency of calories, vitamins and minerals due to inhibition of their absorption.
c. Loss of fluid and electrolytes (mainly K and Ca++); giving rise to hypokalemia and osteomalacia.
d. Complete dependence and resistance to mild purgative due to development of spastic colon.
Contraindication of purgatives Absolute contraindication
a. Acute abdomen (peritonitis, acute appendicitis, intestinal obstruction
b. Weak and collapse condition.
c. Pregnancy.
d. During menstruation.
Choice of purgatives
a. Bulking agents
b. Bisacodyl
c. Senna glycosides
Mechanism of action of Purgatives
A. Bulk purgatives act by increasing volume of non-absorbable solid residue (fibres) retaining water and decreasing the viscosity of bowel to promote large, soft, solid stocil
1. Generally acting within 1-3 hours.
2. No serious unwanted effect.
3. Useful in: anal fissure, haemorrhoids. Diverticular disease, IBS.
B. Osmotic purgatives act by retaining water and electrolytes in the intestinal lumen by the osmotic properties of the drugs or their metabolites, so intestinal transit is increased directly
dr.re to increase intestinal bulk and distend the colon which promote evacuation.
C. Faecal softeners soften the faeces by levering the static tension of fluids in the bowel, whichallows more water remains in the faeces.
D. Useful in anal fissure, haemomhoids.
E. Stimulant purgative act by increasing motility (peristalris) and secretion, so net absorption of electrolytes and H2O are decreased indirectly because of the reduce time for absorption.
Suppositories are conical, solid bodies introduced through the anal orifice for case defecation. Suppository is solid in ordinary temperature but melt at nail temperature Lubricate and stimulate mucosa Ease defecation.
Example: Glycerine suppository, Biscdyl, soap etc. It is used in patients confined to bed and also in children.
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