Laxatives

• What are the four main categories of laxatives mentioned?

  Irritant or stimulants, bulk forming agents, osmotic laxatives, stool softeners
• Name two examples of irritant or stimulant laxatives.

  Bisacodyl and Senna
• What is the function of bulk forming agents?

  They retain water and promote colonic distension, increasing peristalsis
• How do osmotic laxatives work?

  They hold water by osmosis, distending the bowel and increasing intestinal activity
• What is the onset time for oral Bisacodyl?

  1. 10 hours
• What is the onset time for rectal Bisacodyl?

  30 minutes to 2 hours
• What is the role of hydrophilic colloids and dietary fibers in laxatives?

  They are not broken down by digestive enzymes and retain water, promoting colonic distension and peristalsis
• What is the treatment of choice for chronic constipation?

  Bulk forming agents
• How do saline cathartics work?

  They are non-absorbable salts that hold water by osmosis, distending the bowel and increasing intestinal activity
• What is the onset time for saline cathartics like MgSO4?

  1 hour
• What is the purpose of Docusate as a stool softener?

  It mixes aqueous and fatty materials for stool softening and increases water and electrolyte secretion
• What is the onset time for Docusate?

  1. 3 days
• How does Lactulose function as an osmotic laxative?

  It is converted in the colon by bacteria to fructose and galactose, which act as osmotic laxatives
• What is the onset time for Lactulose?

  1. 3 days
• What are the effects of Lactulose in hepatic encephalopathy?

  It inhibits ammonia-producing organisms and converts ammonia to ammonium, reducing systemic ammonia levels
• What is the onset time for glycerin when used rectally?

  Less than 1 hour
• What is the purpose of enemas in bowel preparation?

  They soften stool and distend the bowel for procedures like surgery and endoscopy
• What is the safest laxative for all patients?

  Balanced Polyethylene Glycol (PEG)
• How does PEG work for bowel cleansing?

  It contains inert, non-absorbable, osmotically active sugar designed to prevent significant intravascular fluid shifts
• What are the clinical indications for laxatives?

  Treatment of chronic idiopathic constipation, drug-induced constipation, and prevention in certain populations
• What are the side effects of chronic laxative use?

  • Abdominal cramps
  • Cathartic colon (especially with Senna)
  • Melanosis coli (benign brown pigments)
  • Laxative dependence
  • Bloating and flatus
• What are the potential adverse effects of saline cathartics and Lactulose?

  • Electrolyte disturbance
  • Severe flatulence and abdominal cramps (high dose Lactulose)
  • Cardiac depression in renal failure patients
  • Neuromuscular disorders
  • CNS depression
• What are chloride channel activators used for?

  They are used for chronic constipation and IBS-C
• How does Lubiprostone function?

  It activates chloride channels in the intestines, increasing fluid secretion and motility
• What is the mechanism of action for Methylnaltrexone?

  It antagonizes peripheral µ-opioid receptors without crossing the blood-brain barrier
• What is the role of Prucalopride in treating constipation?

  It is a high-affinity 5-HT4 agonist used for chronic constipation when others fail
• How does Linaclotide work?

  It binds to guanylate cyclase receptors, increasing cGMP and fluid secretion while decreasing pain-sense nerve activity
• What are the indications for using laxatives?

  1. Chronic idiopathic constipation & IBS-C
  2. Drug-induced constipation (e.g., opioids, anticonvulsants)
  3. Prevention in anal piles, pregnancy, elderly, or acute illness
• Lactulose is an osmotic laxative that draws water into the bowel, increasing stool volume.
• Osmotic laxatives help draw water into the intestines to soften the stool and ease its passage.
• Stimulant laxatives promote bowel movements by irritating the intestinal lining, causing contractions.