SUMMARY
The need for careful therapeutic drug monitoring (TDM) arises for measurement of drugs with a narrow therapeutic index (NTIDs), as well as for assuring their safe and controlled replacement with generics. In particular, this category includes anti-epileptic drugs, which use is associated with the range of issues during the management of therapy effectiveness and safety. One of these examples is valproic acid, which therapeutic concentrations vary greatly depending on the individual patient. The need to substantiate the choice and control of individual optimal dosing regimen of drugs, as well as to provide the rational use of generic NTIDs, determines the relevance of the introduction of TLM in the routine practice of standardized medical care for certain categories of patients, and it requires appropriate scientific and practical justification.