11.3: Acid-Base Disorders due to Drugs and Toxins

Drug-induced acid-base disorders:

1. Metabolic acidosis induced by large acid loads
- from exogenous sources (e.g. NH₄Cl, or toxin ingestion)
- from endogenous acid production (e.g. generation of ketoacids or lactic acids by alcohol or phenformin)
- from base loss (eg laxative abuse).

2. Renal tubular acidosis

2. Metabolic alkalosis resulting from exogenous bicarbonate loads or effective extracellular fluid contraction, potassium depletion plus hyperaldosteronism

4. Respiratory acidosis from drug-induced respiratory depression or neuromuscular impairment

5. Respiratory alkalosis from drug-induced hyperventilation

Respiratory Acidosis

• CNS depressants
• Narcotics
• Muscle Relaxants

High Anion Gap Metabolic Acidosis

• Methanol
• Ethylene glycol (due glycolic acid)
• Salicylates
• Paraldehyde
• Phenformin & metformin (lactic acidosis)
• Sodium nitroprusside (lactic acidosis due cyanide)

Renal Tubular Acidosis

• Amphotericin B
• Acetazolamide
• Toluene
• Lithium
• Cyclamate
• Analgesics
• Carbonic Anhydrase Inhibitors (eg acetazolamide)
• Lead
• NSAIDs
• Outdated tetracycline
• Pentamidine in AIDS patients

Other causes of Hyperchloraemic Metabolic Acidosis

• Potassium-sparing diuretics
• Acidifying infusions (eg HCl, NH₄Cl, lysine-HCl & arginine-HCl infusions)
• CaCl₂ ingestion (loss of HCO₃^- due to precipitation of carbonate)

Respiratory Alkalosis

• Salicylates
• Propanidid

Metabolic Alkalosis

• Emetics
• Diuretics