anti diarrheal drugs

• Loperamide is an antidiarrhoeal drug that acts by inhibiting the release of neurotransmitters from nerve endings, thereby reducing intestinal motility.
• Diphenoxylate is used to treat diarrhoea caused by irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD).
• Antidiarrhoeals aim to control the loss of fluids, identify and treat the cause, provide symptomatic relief with antidiarrhoeal drugs, and refer to a physician if symptoms persist for several days, there is blood in the stool, or severe abdominal pain and cramps
• General lines of therapy for diarrhoea include maintenance of fluid & electrolyte balance, oral rehydrating therapy, and zinc tablets as first-line treatment in most cases
• Antidiarrheal drugs are classified into anti-motility agents, adsorbents, and drugs that modify fluid and electrolyte transport
• Anti-motility/ Anticholinergics agents like Atropine, Aminopentamide, Isopropamide, Propantheline, and Methoscopolamine are used to treat tenesmus and vomiting by decreasing intestinal muscle tone and peristalsis of the GI tract
• Atropine is used as an antispasmodic agent to relieve spasm associated with gastrointestinal disorders such as peptic ulceration, gastritis, and colitis.
• Adsorbents/Protectants/Anti-secretory agents like Aluminum hydroxide, Methylcellulose, Bismuth Subsalicylate, and Octreotide are used to control diarrhoea by adsorbing intestinal toxins or microorganisms and/or by coating or protecting the intestinal mucosa
• Antimotility agents like Diphenoxylate, Loperamide, codeine, and opium tincture decrease bowel motility and relieve rectal spasm by inhibiting acetylcholine release and decreasing peristalsis
• Probiotics like Lactobacillus acidophilus help restore and maintain healthy gut flora, suppressing the growth of diarrhoea-causing bacteria
• Antimicrobials are almost routinely prescribed for diarrhoea, but have a limited role in treatment due to bacterial pathogens being responsible for only a fraction of cases and the potential to prolong carrier states
• Diarrhoea caused by E. coli, campylobacter:

  • Norflox, cotrimoxazole, doxycycline, erythromycin
• Shigella enteritis:

  • Associated with blood and mucus
  • Treated with ciprofloxacin, nalidixic acid, norflox
• Salmonella enteritis:

  • Treated with fluroquinolones, ampicillin
• Enterocolitis:

  • Y. pestis
  • Treated with co-trimoxazole, ciprofloxacin
• Regularly useful in Cholera:

  • Tetracycline, co-trimoxazole, especially in children
• Campylobacter jejuni:

  • Treated with norfloxacin, erythromycin
• Clostridium difficile, pseudomembranous colitis:

  • Treated with metronidazole
• Amoebiasis and Giardiasis:

  • Treated with metronidazole, diloxanide furoate
• Constipation is infrequent defecation, often with straining and the passage of hard, uncomfortable stools
• Causes of constipation:

  • Decreased motility in colon due to decrease in water and fiber contents of diet
  • Difficulty in evacuation due to local painful conditions, lack of muscular exercise, drug-induced factors like anticholinergic agents, opioids, iron, antipsychotics
• General measures for treating constipation:

  • Adequate fluid intake
  • High fiber contents in diet
  • Regular exercise
  • Regulation of bowel habit
  • Avoiding drugs causing constipation
• Classification of laxatives:

  • Bulk forming laxatives
  • Osmotic laxatives
  • Stimulant laxatives
  • Stool softeners (lubricants)
• Bulk forming laxatives include:

  • Dietary fibers, bran powder, hydrophilic colloids, psyllium seed, methyl cellulose, carboxymethyl cellulose (CMC)
• Mechanism of action of bulk (fiber) laxatives:

  • Increase the bulk of intestinal contents by water retention, stimulating peristalsis and evacuation of soft stool
• Side effects of bulk (fiber) laxatives:

  • Delayed onset of action, intestinal obstruction, bloating, flatulence, distension, interference with other drug absorption
• Osmotic laxatives:

  • Water soluble compounds, poorly absorbable, increase water content in the large intestine, include sugars like lactulose, salts like magnesium sulfate or hydroxide, sodium or potassium phosphate, polyethylene glycol (PEG)
• Uses of lactulose:

  • Prevention of chronic constipation, hepatic encephalopathy, hemorrhoids
• Mechanism of lactulose in liver cirrhosis:

  • Lactulose → Lactic acid + Acetic Acid → acidification of the colon → ammonia absorption (NH4+)
• Saline laxatives:

  • Poorly absorbable salts, increase evacuation of watery stool, include magnesium sulfate, magnesium hydroxide, sodium phosphate, potassium phosphate
• Uses of balanced Polyethylene Glycol (PEG):

  • Isotonic solution of polyethylene glycol & electrolytes, used for whole bowel irrigation prior to colonoscopy or surgery
• Advantages of balanced Polyethylene Glycol (PEG):

  • Limited fluid or electrolyte imbalance, less flatulence and cramps
• Stimulant laxatives:

  • Act via direct stimulation of enteric nervous system, increasing peristalsis & purgation, include drugs like bisacodyl, castor oil, anthraquinone derivatives
• Side effects of stimulant laxatives:

  • Abdominal cramps, prolonged use may lead to dependence & destruction of myenteric plexus
• Fecal Softeners (Lubricants):

  • Act by decreasing surface tension or by softening the feces, promoting defecation, include drugs like docusate, glycerin, paraffin oil
• Side effects of paraffin oil:

  • Not palatable, impairs absorption of fat-soluble vitamins
• Side effects of diphenoxylate include drowsiness, dry mouth, constipation, and difficulty urinating.