Faut-il proposer une adaptation posologique lors d'une antibiothérapie ?

While we are confronted with the major increase in antibiotic resistance, the preservation of existing antibiotics has become an absolute necessity both to achieve therapeutic success and to limit the risks of the emergence of resistance. The optimization of antibiotic use and dosages must have a threefold objective: guarantee antibacterial efficacy, limit toxicities and limit emergence of resistant strains. However, with the increase in the number of multipathological patients, particularly those with renal or hepatic impairment, the increase in the number of patients with extreme weights and the use of antibiotics with narrower therapeutic margins, the adaptation of antibiotic dosages is becoming increasingly important. By reminding some principles of pharmacokinetics and pharmacodynamics of antibiotics (PK/PD), the necessary objectives for clinical effectiveness of most antibiotic classes are reviewed and several examples of situations where dosage adjustments are necessary will be given. In particular, adjustment of antibiotic dosages in obese patients will be discussed. Adaptation is not limited to the adaptation of the total daily dose. The PK/PD parameters also tell us that the mode of administration (intermittent versus continuous, number of injections per day, etc.) is also an essential point to consider. By taking examples concerning some molecules, infections and difficult clinical situations, we review situations in which dosage adjustments appear necessary.