Pharmacokinetic is sometimes described as what the patient's body does to the drug. It comprises the processes and time course of liberation, adsorption, distribution, metabolism and excretion of the drug. PK data can be used to link the drug exposure to the observed efficacy and safety. Knowledge of drug levels helps in choosing the appropriate application route, dosage, and schedule of a drug and may furthermore indicate immunogenicity effects. The assessment of a drug’s PK is therefore a very important tool during pre-clinical and clinical drug development.