Protein binding and its significance in antibacterial therapy

Serum protein binding of antimicrobials can reduce antimicrobial activity, restrict tissue distribution, and delay drug elimination. Binding percentages of 80 per cent or more have the potential to significantly reduce free drug levels and affect therapeutic efficacy in patients. However, binding-induced alterations in drug elimination and differences in intrinsic antibacterial activity can often compensate for the inhibitory effect of high serum protein binding. Knowledge of the extent of protein binding does allow one to estimate, for a given level of total drug, the concentration of active drug in serum and most extravascular fluids.