Zero order kinetics is followed by all of the following drugs EXCEPT

Zero order (linear) kinetics; The rate of elimination remains constant irrespective of drug concentration, Clearance decreases with increase in concentration, or a constant amount of the drug is eliminated in unit time, e.g. ethyl alcohol, methanol. The elimination of some drugs approaches saturation over the therapeutic range, kinetics changes from first order to zero order at higher doses. As a result plasma concentration increases dispropoionately with an increase in dose, as occurs in case of phenytoin, tolbutamide, theophylline, warfarin, aspirin, digoxin Barbiturates follow first order kinetics. Ref:KD Tripathi pharmacology 7th edition (page.no: 31)