The scientific and practical substantiation of the therapeutic drug monitoring procedure: validation of the analytical method of valproic acid measurement

V. Ye. Dobrova, O. S. Popov, S. V. Misiurova


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.

Aim. To provide the scientific and practical substantiation of the procedure of TDM by validation of the laboratory method for determining the concentration of valproic acid in the blood plasma.

Materials and methods. Analytical, statistical and biological methods were used in the study. Measurement of valproic acid concentration in a standardized sample of the blood plasma was performed by the photometric method using reagents produced by SIEMENS, Inc., USA and the control serum “Chemical control, level1” produced by Bio-Rad, Inc., USA. Measurements were made by a Siemens Bio Dimension RxL Max automatic biochemical analyzer.

Results. The limits of intra-laboratory reproducibility by the factor of the laboratory assistant have been estimated as R = 3.25. The assessment of the repeatability and reproducibility of the method by the time factor and in different concentration ranges has shown the absence of gross errors and statistically significant differences in the measurements. It has been found that in the range of 73.8 ± 110 µg/ml valproic acid concentration values determined by this method using the Siemens Dimension RxL Max device can be considered accurate and reliable. The linearity of this method within the range of the concentrations measured has been also proven; it confirms the possibility of its use for measuring the concentration of valproic acid in the blood plasma.

Conclusions. The scientific and practical substantiation obtained is necessary for the proper implementation of TDM in the process of providing medical care to particular categories of patients to optimize the individual dosing regimen of NTIDs. In addition, validation of the TDM method allows using it for assuring the safe and controlled generic replacement of NTIDs. The results of the work can be used in the process of further improvement and development of new analytical methods for TDM of valproic acid, as well as other NTIDs.


therapeutic drug monitoring; validation; laboratory method; narrow therapeutic index drugs; valproic acid


Touw, D. J., Neef, C., Thomson, A. H., & Vinks, A. A. (2005). Cost-Effectiveness of Therapeutic Drug Monitoring. Therapeutic Drug Monitoring, 27(1), 10–17.

Sokolov, A. V. (2002). Kachestvennaja klinicheskaja praktika, 1, 6–11.

CFR—Code of Federal Register 21, section 320.33 (21CFR320.33) Criteria and evidence to assess actual or potential bioequivalence problems. – Available at : = 320.33

Tamargo, J., Le Heuzey, J. Y., Mabo, P. (2015). Narrow therapeutic index drugs: a clinical pharmacological consideration to flecainide. European Journal of Clinical Pharmacology. 71(5), 549–567. https://doi:0.1007/s00228-015-1832-0

Kang, J.-S., & Lee, M.-H. (2009). Overview of Therapeutic Drug Monitoring. The Korean Journal of Internal Medicine, 24(1), 1.

Greenberg, R. G., Melloni, C., Wu, H., Gonzalez, D., Ku, L., Hill, K. D., … Guptill, J. T. (2016). Therapeutic Index Estimation of Antiepileptic Drugs. Clinical Neuropharmacology, 39(5), 232–240. https://doi:10.1097/WNF.0000000000000172

Zupanets, I. A., Usenko, V. O., Kryachok, I. V., Kosyachenko, K. L., Strashniy, V. V., Savich, S. A., Tarasenko, O. O. (2017). Therapia, 7-8 (122), 38–40.

Van Gelder, T. (2011). European Society for Organ Transplantation Advisory Committee Recommendations on Generic Substitution of Immunosuppressive Drugs. Transplant International, 24(12), 1135–1141. https://doi:10.1111/j.1432-2277.2011.01378.x

Glauser, T. A., & Pippenger, C. E. (2000). Controversies in Blood-level Monitoring: Reexamining Its Role in the Treatment of Epilepsy. Epilepsia, 41(s8), S6–S15.

Jannuzzi, G., Cian, P., Fattore, C., Gatti, G., Bartoli, A., … Monaco, F. (2000). A Multicenter Randomized Controlled Trial on the Clinical Impact of Therapeutic Drug Monitoring in Patients with Newly Diagnosed Epilepsy. Epilepsia, 41(2), 222–230.

Methaneethorn, J. (2018). A systematic review of population pharmacokinetics of valproic acid. British Journal of Clinical Pharmacology, 84(5), 816–834. https://doi:10.1111/bcp.13510

Derzhavniy reestr likarskih zasobiv. (n.d.). Available at:

Van Gelder, T., Meur, Y. L., Shaw, L. M., Oellerich, M., DeNofrio, D., Holt, C., … Mamelok, R. D. (2006). Therapeutic Drug Monitoring of Mycophenolate Mofetil in Transplantation. Therapeutic Drug Monitoring, 28(2), 145–154.

Mіsiurova, S., Dobrova, V., Svid, N., Otrishko, I., & Sakharova, T. (2018). Quality assurance of the biochemical studies using validation procedures in the Laboratory of Clinical Diagnostics of the ClinicalDiagnosticCenterof the National University of Pharmacy on the example of the method for determining the level of total and direct bilirubin in biological fluids. Klìnìčna farmacìâ, 22(3), 52–57. https://doi:10.24959/cphj.18.1468

Dobrova, V. Ye., Zupanets, K. O., Misyurova, S. V., Mazur, N. S. (2015). Sistemy obrobki informatsiyi, 2(127), 104–107.

GOST Style Citations

1. Cost-effectiveness of therapeutic drug monitoring: a systemic review / D. J. Touw, C. Neef, A. H. Thomson et al. // Therapeutic Drug Monitoring. – 2005. – Vol. 27. – P. 10–17. 


2. Соколов, А. В. Терапевтический лекарственный мониторинг / А. В. Соколов // Качественная клиническая практика. – 2002. – № 1. – С. 6‑11.


3. CFR—Code of Federal Register 21, section 320.33 (21CFR320.33) Criteria and evidence to assess actual or potential bioequivalence problems. [Электронный ресурс]. – Available at : = 320.33


4. Tamargo, J. Narrow therapeutic index drugs: a clinical pharmacological consideration to flecainide / J. Tamargo, J. Y. Le Heunzey, P. Mabo // Eur. J. of Clinical Pharmacol. – 2015. – Vol. 71 (5). – P. 549–567. https://doi:0.1007/s00228-015-1832-0


5. Kang, J. S. Overview of therapeutic drug monitoring / J. S. Kang, M. H. Lee // Korean J. of Internal Medicine. – 2009. – Vol. 24 (1). – P. 1–10.


6. Therapeutic index estimation of antiepileptic drugs: a systematic literature review approach / R. G. Greenberg, C. Melloni, H. Wu et al. // Clinical Neuropharmacol. – 2016. – Vol. 39 (5). – P. 232–240. https://doi:10.1097/WNF.0000000000000172


7. Класифікація лікарських засобів на підставі їхньої еквівалентності / І. А. Зупанець, В. О. Усенко, І. В. Крячок та ін. // Therapia. – 2017. – № 7-8 (122). – С. 38‑40.


8. Van Gelder, T. M. European Society for Organ Transplantation. Advisory Committee Recommendations on Generic Substitution of Immunosuppressive Drugs / T. van Gelder // Transplant. International. – 2011. – Vol. 24. – P. 1135–1141. https://doi:10.1111/j.1432-2277.2011.01378.x


9. Glauser, T. A. Controversies in blood-level monitoring: reexamining its role in the treatment of epilepsy / T. A. Glauser, C. E. Pippenger // Epilepsia. – 2000. – Vol. 41 (Suppl. X). – P. 1–5. 


10. A multicenter randomized controlled trial on the clinical impact of therapeutic drug monitoring in patients with newly diagnosed epilepsy / G. Jannuzzi, P. Cian, C. Fattore et al. // Epilepsia. – 2000. – Vol. 41 (2). – P. 222–230. 


11. Methaneethorn, J. A systematic review of population pharmacokinetics of valproic acid / J. Methaneethorn // British J. of Clinical Pharmacol. – 2018. – Vol. 84 (5). – P. 816–834. https://doi:10.1111/bcp.13510


12. Державний реєстр лікарських засобів. [Електронний ресурс.] ‑ Available at :


13. Therapeutic drug monitoring of mycophenolate mofetil in transplantation / T. M. van Gelder, Y. M. Le Meur, L. M. Shaw et al. // Therapeutic Drug Monitoring. – 2006. ‑ Vol. 28. – P. 145–154. 


14. Забезпечення якості біохімічних досліджень за допомогою валідаційних процедур у лабораторії клінічної діагностики Клініко-діагностичного центру Національного фармацевтичного університету на прикладі методик визначення рівнів загального та прямого білірубіну у біологічних рідинах / С. В. Місюрьова [та ін.] // Клінічна фармація. – 2018. – Т. 22, № 3. – С. 52–57. https://doi:10.24959/cphj.18.1468


15. Забезпечення якості гематологічних досліджень на прикладі валідації методики визначення концентрації гемоглобіну в біологічних рідинах гемоглобінцинідним методом / В. Є. Доброва, К. О. Зупанець, С. В. Місюрьова, Н. С. Мазур // Система обробки інформації. – 2015. – Вип. 2 (127). – С. 104–107.

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Abbreviated key title: Clin. pharm.

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