Inorganic Pharmaceutical Chemistry: Diarrhea Treatment

Inorganic Pharmaceutical Chemistry

• Gastrointestinal agents commonly used to treat mild diarrhea
• Diarrhea is a symptom, not a disease.
• Factors that impair digestion and absorption lead to increased bulk in the intestinal tract, stimulating peristalsis and causing diarrhea.
• Diarrhea can be acute or chronic, with different causes.
• Dehydration and electrolyte imbalances are complications of diarrhea, particularly for young and elderly individuals.
• Antidiarrheal agents treat symptoms and occasionally causes, but not complications.
• Most antidiarrheal products contain adsorbent-protectives, antispasmodics, and possibly antibacterial agents.
• The ideal antispasmodic agent directly acts on smooth muscles of the gut to decrease peristalsis and increase segmentation.
• Antibacterials are effective when there's an intestinal infection.
• Adsorbent-protectives bind toxins, bacteria, and viruses, and also provide a protective mucosal coating.
• Some adsorbent-protectives include bismuth salts, special clays, and activated charcoal.

Mechanism of Adsorption

• Adsorption: substance (adsorbate) adheres to the surface of another substance (adsorbent).
• Activated charcoal, kaolin, and specific clays act as adsorbents in the gut.

Types of Adsorption

• Physical Adsorption: occurs due to Van der Waals forces, which are weak and non-specific, leading to reversible adsorption.
• Chemical Adsorption: involves stronger chemical bonds between adsorbent and adsorbate, possibly irreversible, with electron exchange or sharing.

Factors Affecting Adsorption

• Surface Area and Porosity: Adsorbents like activated charcoal have high surface areas and porous structures, crucial for adsorbing substances.
• Polarity: Adsorption is influenced by the polarity of molecules. Polar adsorbents bind polar molecules, and non-polar adsorbents bind non-polar substances.
• pH Sensitivity: The surrounding environment's pH affects adsorption efficiency. For example, bismuth salts' solubility and adsorption vary with pH.

Bismuth-Containing Products

• Utilization of bismuth salts as antidiarrheals is mainly based on tradition.
• Bismuth subcarbonate is used as an antacid.
• Bismuth salts are water-insoluble, but a small amount dissolves, acting as a mild astringent and antiseptic.
• Intestinal hydrogen sulfide interacts with bismuth salts to form bismuth sulfide, causing black stools.
• Bismuth compounds provide dual action: they adsorb toxins and bacteria while creating a protective intestinal barrier.

Bismuth Subnitrate

• A white, slightly hygroscopic powder, insoluble in water and alcohol, but soluble in acids.
• Assayed in terms of bismuth trioxide.
• Incompatibility with tragacanth, which can be overcome by adding sodium biphosphate or trisodium phosphate.
• May inhibit pepsin.
• Used as a component of Milk of Bismuth, where it acts as a mild astringent-protective.

Milk of Bismuth

• Contains bismuth hydroxide and bismuth subcarbonate suspended in water.
• Produced by converting bismuth subnitrate to bismuth nitrate, then treated with ammonium carbonate and ammonia solution.
• Classified as an astringent and antacid.

Bismuth Subcarbonate

• White or pale yellowish-white powder, odorless and tasteless.
• Stable in air but affected by light, insoluble in water and alcohol, but soluble in acids.
• Assayed in terms of bismuth trioxide.

Nonofficial Bismuth Compounds

• Bismuth Subgallate
• Bismuth Subsalicylate
• Bismuth Ammonium Citrate

Activated Clays and Other Adsorbents

• Clays with excellent adsorbent properties are used industrially and clinically for mild, short-duration diarrhea.

Kaolin

• Native hydrated aluminum silicate, powdered and free from gritty particles.
• Soft, white, or yellowish-white powder, with an earthy taste.
• Binds toxins and bacteria through physical and chemical adsorption.
• Insoluble in water, acids, and alkali hydroxides.
• Often used with pectin (Kaopectate®, Kao-Con®) as an adsorbent.
• Reported to interfere with intestinal absorption of lincomycin.

Activated Charcoal

• Used as an adsorbent for diarrhea and as an antidote for specific poisoning.
• Works primarily through physical adsorption.
• Highly porous, effectively binding large organic molecules such as toxins, chemicals, and drugs.

Saline Cathartics

• Agents that accelerate and increase bowel evacuation.
• Laxatives are mild cathartics.
• Widely used, but often abused and overpromoted.
• Properly used to:
  • Ease defecation with painful hemorrhoids or rectal disorders.
  • Avoid straining and pressure in patients with hernias.
  • Reduce blood pressure during defecation in patients with hypertension or other circulatory diseases.
  • Relieve acute constipation.
  • Remove solid material before certain roentgenographic studies.
• Sodium-containing saline cathartics are not suitable for long-term use in low-sodium diets.
• Magnesium salts should be restricted for those with impaired renal function due to magnesium absorption and CNS depressant effects.

Official Saline Cathartics

• Sodium Biphosphate:
  • Colorless crystals or white crystalline powder, odorless, slightly deliquescent, acid to litmus.
  • Dissolves in water, dissociating into ions.
  • Used as urinary acidifier and cathartic (Phospho-Soda, Vacuetts, and Sal Hepatica).
• Sodium Phosphate:
  • Colorless or white granular salt, effervesces in moist air, solutions are alkaline.
  • Freely soluble in water, poorly absorbed in intestines.
  • Used as a saline cathartic (Fleet Enema, Phospho-Soda).
• Dried Sodium Phosphate:
  • Nearly anhydrous white powder, absorbs moisture readily, freely soluble in water, insoluble in alcohol.
  • Used as a saline cathartic in Effervescent Sodium Phosphate, a mixture with carbonates, tartaric acid, and citric acid.
  • Dried form prevents premature reactions and ensures a pleasant flavor.

This quiz covers gastrointestinal agents used to treat mild diarrhea, exploring the causes, symptoms, and treatment options. Learn about the role of antidiarrheal agents and how they help manage diarrhea-related complications. Test your knowledge on the various types of agents and their mechanisms of action in the gastrointestinal system.