Drug-induced acid-base disorders may be classified into four categories with respect to the mechanism. 1. Metabolic acidosis is induced by a large acid loads incurred from exogenous sources (e.g. NH4Cl, or toxin ingestion) or endogenous acid production (e.g. generation of ketoacids or lactic acids by alcohol or phenformin) or base loss (e.g. abuse of laxatives). 2. Metabolic alkalosis results from exogenous bicarbonate loads (e.g. milk-alkali syndrome) or effective extracellular fluid contraction, potassium depletion plus hyperaldosteronism (e.g. vomiting, diuretics, or licorice). 3. Renal tubular acidosis is induced by the drugs which mainly impair proximal and/or distal tubules (e.g. vitamin D, NSAID, acetazolamide or amphotericin B). 4. Respiratory acidosis or alkalosis results from drug-induced respiratory center depression or neuromuscular impairment (e.g. anesthetic, sedative overdosage or curare) or hyperventilation (salicylates, paraldehyde, epinephrine, or nicotine).