Drug Elimination – USMLE exams
There are two types of drug elimination: Zero Order and 1st Order
Drug Clearance = Rate of elimination / Plasma Drug Concentration
1st Order Elimination – In 1st order elimination, the rate of drug elimination is proportional to the plasma concentration (Cp) of drug. Thus with more drug concentration there is more drug elimination, if there is less drug concentration there is less drug elimination. Most drugs are eliminated by 1st order elimination.
Zero Order Elimination – In Zero order elimination, the fraction of drug elimination remains constant, no matter how high the drug concentration. There are less drugs eliminated with zero-order elimination, two examples are alcohol and aspirin.