多回投与パラメータの決定：定常状態、最小濃度および最大濃度

The accumulation factor, expressed as 1/(1 - e-kτ), accounts for repeated doses of gentamicin and reflects the drug's progressive build-up until steady state is reached. It incorporates the elimination rate constant k and dosing interval τ, enabling clinicians to predict maximum plasma concentrations after multiple infusions and optimize therapeutic outcomes.

Trough plasma concentration is the drug level immediately before the next gentamicin infusion at steady state. This parameter is critical for ensuring plasma levels remain above the minimum inhibitory concentration, reducing treatment failure risk. Calculating trough concentration helps clinicians assess whether dosing regimens maintain adequate therapeutic coverage throughout the dosing interval.

Infusion duration (tinf) directly affects the initial plasma drug concentration calculation after a single gentamicin infusion. A one-hour infusion allows for controlled drug delivery, minimizing toxicity while ensuring therapeutic efficacy. The infusion duration is incorporated into equations that predict plasma concentrations, enabling precise adjustments in therapeutic drug monitoring.

Exponential decline describes how gentamicin plasma concentration decreases over time after infusion completion, influenced by the elimination rate constant k and time elapsed since infusion ended. This mathematical relationship enables clinicians to predict plasma levels at any point during the dosing interval, supporting informed decisions about dose timing and therapeutic drug monitoring adjustments.

The dosing interval τ directly influences the accumulation factor and maximum plasma concentration at steady state. Shorter intervals increase drug accumulation, raising maximum concentrations, while longer intervals allow greater elimination between doses. Understanding this relationship helps clinicians select appropriate dosing intervals for gentamicin therapy, balancing efficacy with toxicity risk.

Steady-state concentration is achieved after multiple gentamicin infusions when the amount of drug eliminated between doses equals the amount administered, resulting in consistent maximum and minimum plasma levels. At steady state, the maximum concentration is calculated using the accumulation factor, allowing clinicians to predict drug behavior and make precise therapeutic adjustments.

Pharmacokinetic equations calculate plasma concentrations at specific time points—after single infusions, at steady-state maximum, and at trough levels—enabling precise therapeutic drug monitoring. These calculations account for infusion duration, dosing interval, and elimination kinetics, allowing clinicians to optimize gentamicin therapy by adjusting doses or intervals to maintain therapeutic efficacy while minimizing toxicity risk.