Individualization of piperacillin dosage based on therapeutic drug monitoring with or without model-informed precision dosing: a scenario analysis.

Background: Model-informed precision dosing (MIPD) combines population pharmacokinetic knowledge with therapeutic drug monitoring (TDM) to optimize dosage adjustment. It could improve target concentration attainment over empirical TDM, still widely practised for broad-spectrum antibiotics.

Objectives: To evaluate the respective performance of TDM and MIPD in achieving target piperacillin exposure.

Methods: Measurements from 80 courses of intermittent piperacillin infusions, each with two TDM samples, were retrospectively submitted to our MIPD software TUCUXI. We considered six dosage adjustment strategies: identical dosage for all (4000 mg q8h), actual initial dosage (chart-based), actual empirical adjustment following first TDM, a priori MIPD-based dosage, a posteriori MIPD-based adjustment after first TDM and MIPD including both TDM measurements. Dosing strategies were compared regarding daily dosage, trough levels distribution and PTA (with target trough 8-32 mg/L).

Results: Median trough concentration fell within 8-32 mg/L for all strategies except a priori MIPD-based dosage (42 mg/L). Distributions of trough concentrations predicted with the six dosage adjustment strategies showed significant differences, with both a posteriori MIPD-based strategies best reducing their standard deviation (P < 0.001). PTA of 32%, 32%, 55%, 29%, 83% and 94% were estimated, respectively for the six strategies (P < 0.001). Poor performance of a priori MIPD-based dosage did not hinder a posteriori MIPD-based strategies from significantly improving target attainment.

Conclusions: Whilst empirical TDM improves exposure standardization and target attainment compared with no TDM, MIPD can still bring further improvement. Prospective trials remain warranted to confirm MIPD benefits not only on target attainment but also on clinical endpoints.