Describe the underlying processes in diarrhea and constipation and correlate them with the types of drugs used to treat these conditions.

Underlying Processes

 Diarrhea:

 Increased Intestinal Motility: Diarrhea simply can be defined as the passing more number of stools than is normal for a given individual and the passing of loose stools. This can be due to increased frequency of contraction of the intestines, which in so doing minimizes the time taken for food and waste cycling within the intestines and therefore reduces water retention.

 Altered Fluid and Electrolyte Transport: Diarrhea can arise especially when there is perceived inflammation or infection of the intestinal mucosa, in that the normal functions of the mucosa lead to the secretion of more fluids and electrolytes in the lumen of the intestines than is normal. This leads to diarrhoea which may be loose and watery in nature with bad smell.

 Malabsorption: Any condition that alters nutrient uptake (for instance, celiac disease, Crohn’s disease), will compromise the amount and efficiency of nutrients and fluids that are absorbed and this leads to diarrhea.

 Constipation:

 Decreased Intestinal Motility: The symptoms of constipation are where one experiences a long time frame between bowel movements and passes out dry and firm stool. This is due to decreased peristaltic movements leading to slow, hence, long transit time and excessive water content from the feces.

 Increased Colonic Absorption: Many people suppose that the colon is solely responsible for osmosis of water in to the waste material. In constipation, this process takes long, resulting to the formation of hard, dry feces that are inclined to be expelled.

 Obstruction or Structural Issues: Structural problem such as the diminution of colon mobility , tumors or strictures are also likely to lead to constipation seeing that they will hinder the passage of stool through the large intestine.

 Correlation with Drug Types

 Diarrhea Treatment:

 Anti-Motility Agents:

 Examples: Imodium , Lomotil and others include Diphenoxylate with atropine.

 Mechanism: These drugs act as anti-motility and anti-secretory agents by decreasing the contractions of the bowel and increasing the amount of fluid to be absorbed. Opioid receptors forming in the gut and reduce peristalsis since Histaamine has excitatory effects in the gut and it blocked.

 Adsorbents:

 Examples: Kaolin-pectin, activated charcoal.

 Mechanism: Adsorbents interact with toxins and pathogens and so have reduced impact on the gastrointestinal tract while also contributing to the formation of firmer stools.

 Antisecretory Agents:

 Examples: Bismuth subsalicylate (Pepto-Bismol).

 Mechanism: These agents decrease the secretion of substances in the intestine and its inflammation leading to a decrease in the frequency and state of liquidity of the faecal mass.

 Probiotics:

 Examples: Lactobacillus, Bifidobacterium.

 Mechanism: They are useful in altering the bowel, especially when inflammation is as a result of antibiotics or gastrointestinal infections.

 Constipation Treatment:

 Laxatives:

 Types:

 Bulk-Forming Laxatives: Fiber supplements which may be taken are psyllium and methyl cellulose – psyllium is sold under the trade name of Metamucil while methyl cellulose is sold under the trade name of Citrucel.

 Mechanism: These help to bulking the stools by the process of water absorption and stimulate the peristalese movements and promote bowel movements.

 Stimulant Laxatives: Bisacyclyl (Dulcolax), Senna (Senokot).

 Mechanism: These stimulate the intestinal mucosa and as such encourage peristalsis and making of bowel movements.

 Osmotic Laxatives: Dulical, Lactulose, Polyethylene glycol (MiraLax).

 Mechanism: These pull water into the bowel which makes the stool to become more liquid making it to pass easily.

 Emollient Laxatives: Docusate sodium (Colace).

 Mechanism: This lower stool surface tension, enabling water and fats to get into and hence lubricate the stools.

 Chloride Channel Activators:

 Examples: Lubiprostone (Amitiza).

 Mechanism: These stimulate more water/chloride ions into the intestines through the enhancement of chloride ion channels hence contributes to the laxative effects.

 Guanylate Cyclase-C Agonists:

 Examples: Linaclotide (Linzess).

 Mechanism: These raise intracellular cGMP level – coincides with increase in both secretory fluid and bowel motility