Target beta-lactam blood concentrations

The target trough plasma concentration for beta lactams is usually an unbound plasma concentration higher than the minimum inhibitory concentration of the pathogen. A higher target concentration is required for continuous infusions – seek expert advice.

Laboratories may report beta-lactam plasma concentrations as total or unbound. Measuring the total concentration is generally sufficient because, for most beta lactams, this correlates with the unbound concentration. However, for drugs with over 80% protein binding (eg ceftriaxone, ertapenem, flucloxacillin), it is preferable to measure the unbound concentrationWong 2013.

If beta-lactam concentration monitoring is required, see the International Association for Therapeutic Drug Monitoring and Clinical Toxicology position paper for information about the recommended target concentrations.