Therapeutic drug monitoring

Therapeutic drug monitoring is a process aimed at optimizing pharmacotherapy for an individual patient based on the measurement of drug concentration in the blood, pharmacokinetic principles, and pharmacodynamic criteria.

This allows for:

verification of previously used drug dosage regimen
correct dosage regimen to reduce drug toxicity
improving the effectiveness of the treatment and reducing its costs
safety of using high doses of potentially highly toxic drugs

Pharmacokinetics of a drug refers to the study of its absorption, distribution, metabolism, and excretion, as well as the influence of physiological, pathophysiological, and environmental factors and concomitantly used other drugs on the course of these processes. This information is necessary for proper interpretation of the results obtained, considering the patient's clinical state and the time of blood sampling for analysis.

Not all drugs require therapeutic drug monitoring. Drugs that are monitored include anticonvulsants, antiarrhythmics, cytotoxic drugs, antidepressants, immunosuppressants, which are characterized by:

potent action with a narrow therapeutic index, i.e., a small range between therapeutic and toxic concentrations
non-linear pharmacokinetics (lack of a proportional relationship between concentration and dose
large inter-individual variability in concentrations following a usual dose
the potential for numerous interactions with other drugs used concomitantly

TDM provides an alternative to empirical dosage selection based on trial and error, as well as a rational basis for individualising drug dosing and accelerating the achievement of the therapeutic goal.

Methods used in therapeutic drug monitoring:

Abbreviation	Method
AED_SP	Quantification of antiepileptic drugs in plasma/serum by LC-MS/MS technique