Penicillins

Penicillins are among the most widely used class of antibiotics, utilised for a wide variety of clinical indications, including critical illnesses and sepsis. Clinical efficacy and the prevention of the emergence of resistance are critically dependent upon the correct dosing strategy in order to meet the required time-dependent pharmacodynamic target. Penicillins mainly experience increases in volume of distribution and renal clearance in obese patients, such that standard doses may not be sufficient to achieve target attainment. The dosing recommendation for penicillin antibiotics in obesity is, however, complex and lacking clinical evidence. This chapter will review the current literature and make suggestions for altered dosing for commonly prescribed penicillin antibiotics. Fortunately, given the relative safety profile of the penicillin antibiotics, greater flexibility at upper range of the dosing schedule, or frequency of administration, is available. Strategies such as extended and continuous infusions are explored, together with reference to front-loading dosing, therapeutic drug monitoring and Bayesian estimation techniques and software to promote individualised drug dosing. Critical illness in obese patients warrants careful consideration of penicillin dosing and must take into consideration the pharmacokinetic and pharmacodynamic changes and altered targets.