Zero-order kinetics occur in the following drug with high dose: (A) Phenytoin and Theophylline, (B) Digoxin and Propranol, (C) Amiloride and Probenecid, (D) Lithium and Theophylline
Answer is A. zero order kinetics -the rate of elimination remains constant irrespective of drug concentration, clearance decreases with increase in concentration, or a constant amount of drug is eliminated in unit time The elimination of some drugs changes from first order to zero order at higher doses eg ; Phenytoin, Tolbutamide, Theophylline, Warfarin, DIGOXIN, aspirin ref; KD Tripathi Pharmacology 7th edition (page no;31 )