Antibiotic pharmacokinetics in surgery Pharmacokinetics is the study of variables that affect drug concentrations at the effector site. The descriptive terms peak concentration, elimination half-life, volume of distribution, and bioavailability are commonly used to express pharmacokinetic variability among drugs used in patient care. The pharmacokinetic characteristics of drugs are important for surgeons to understand because they represent differences that may assume clinical significance when selecting antibiotics for preoperative preventive indications. In addition, the changing hemodynamic pattern of the stressed and septic patient may result in changing pharmacokinetic patterns for an antibiotic, which, in turn, may require changes in the dosing regimen during the course of treatment. 