Questions
2 questions in typical university papers
Difficulty
Medium
Importance
Core topic for B.Pharm pharmacology and medicinal chemistry
Overview
Acid-Base and Electrolyte pharmaceuticals are critical inorganic compounds used in clinical settings to maintain physiological pH balance and fluid homeostasis. Understanding these agents is essential for pharmacy students as they form the foundation of therapeutic interventions for gastrointestinal disorders and systemic electrolyte imbalances.
Antacids
Antacids are basic compounds that neutralize gastric acid, providing symptomatic relief in conditions like hyperacidity and peptic ulcers. They are classified as systemic or non-systemic based on their solubility and systemic absorption profile.
- Systemic antacids: Sodium Bicarbonate (rapidly absorbed)
- Non-systemic antacids: Aluminum Hydroxide, Magnesium Hydroxide
- Combination therapy: Al(OH)3 + Mg(OH)2 to balance constipating and laxative effects
- Mechanism: Neutralization reaction (Acid + Base = Salt + Water)
- Acid neutralizing capacity (ANC) test is the primary quality control parameter
Electrolyte Replacement Therapy
These preparations are designed to restore the concentration of vital ions in the extracellular and intracellular fluids. They are typically administered to treat dehydration, metabolic acidosis, or alkalosis.
- Sodium Chloride: Maintains osmotic pressure and extracellular fluid volume
- Potassium Chloride: Critical for nerve conduction and muscle function
- Calcium Gluconate: Used for hypocalcemia and magnesium toxicity
- Magnesium Sulfate: Used as a laxative and in eclampsia management
- Formulated as oral rehydration salts (ORS) or intravenous infusions
Physiological Buffers and Acid-Base Balance
The body maintains blood pH between 7.35 and 7.45 through complex buffer systems. Pharmacological intervention is required when renal or respiratory compensation mechanisms fail to correct pH deviations.
- Bicarbonate buffer system (Primary extracellular buffer)
- Henderson-Hasselbalch equation: pH = pKa + log([Salt]/[Acid])
- Metabolic Acidosis: Treated with Sodium Lactate or Sodium Bicarbonate
- Metabolic Alkalosis: Treated with Ammonium Chloride
- Respiratory compensation: Regulated via CO2 expiration
Formula Sheet
pH = pKa + log([base]/[acid])
NaHCO3 + HCl -> NaCl + H2O + CO2
Al(OH)3 + 3HCl -> AlCl3 + 3H2O
Exam Tip
Always pair Aluminum and Magnesium antacids in your answer to explain the 'balanced' formulation approach for gastrointestinal comfort.
Common Mistakes
- Confusing the laxative effect of Magnesium salts with the constipating effect of Aluminum salts in combination antacids.
- Neglecting the significance of systemic absorption in Sodium Bicarbonate, leading to risks of metabolic alkalosis.
- Failing to mention the Acid Neutralizing Capacity (ANC) when asked about quality control of antacids.
More Revision Notes
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