The pharmacology of any xenobiotic is a complex set of processes that is frequently divided into two categories: pharmacokinetics and pharmacodynamics. These two processes encompass the various steps that the body takes to transform the drug to facilitate its excretion (pharmacokinetics) and the interactions of the drug with the body which result in the observed effects (pharmacodynamics). The study of these processes includes the determination of kinetic parameters to describe the rate of elimination of the drug from the body, binding affinities to describe the interaction of the drug with endogenous receptors, and the determination of enzymes that are instrumental in these processes.