Zero order kinetics means:
Ans. a (A constant amount of drug is eliminated per unit time). (Ref. Pharmacology by KD Tripathi 6th/33, fig. 3.5)ZERO ORDER ELIMINATION# The metabolic pathways responsible for alcohol metabolism are rapidly saturated and that clearance is determined by how fast these pathways can work. The metabolic pathways work to their limit.# This is known as zero order kinetics: a constant amount of drug is eliminated per unit time,# This form of kinetics occurs with several important drugs at high dosage concentrations:- Phenytoin,- Salicylates,- Theophylline, and- Thiopentone (at very large doses).# Because high dose thiopentone is very slow to clear, we no longer use it in infusion for status epilepticus.FIRST ORDER ELIMINATION# A constant fraction of the drug in the body is eliminated per unit time.# The rate of elimination is proportional to the amount of drug in the body.# The majority of drugs are eliminated in this way.Elimination of drugsZero-order elimination Rate of elimination is constant regardless of C (constant amount of drug eliminated per unit time). Cp | linearly with time. Examples of drugs--ethanol, phenytoin, and aspirin (at high or toxic concentrations).First-order elimination Rate of elimination is proportional to the drug concentration (i.e.., constant fraction of drug eliminated per unit time). Cp | exponentially with time