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In contrast to an HPLC assay, steps Steps such as solvent extraction, solvent or derivation must be executed prior to a HPLC assay, which takes significant more time<ref name=”[29]”> Free Valproic Acid Assay (2014, April). Retrieved from November 3, 2019, at [https://www.cadth.ca/sites/default/files/pdf/lab-tests/06_Free_Valproic_Acid_Assay_e.pdf/“https://www.cadth.ca/sites/default/files/pdf/lab-tests/06_Free_Valproic_Acid_Assay_e.pdf”].</ref>
→State of the art
The recommended levels of unbound valproate are 6-22 µg/mL in blood <ref name=”[20]”> Valproic Acid (2018, October 1) , at [https://labtestsonline.org/tests/valproic-acid“https://labtestsonline.org/tests/valproic-acid”].</ref>. For epilepsy patients, the range for the treatment of total valproate should be 50-100 µg/mL. Overall, if a patient has a VPA concentration that falls within this range, does not have recurrent seizures and has minimal side effects, then the dose is said to be suitable<ref name=”[20]”> Valproic Acid (2018, October 1) , at [https://labtestsonline.org/tests/valproic-acid“https://labtestsonline.org/tests/valproic-acid”].</ref>
. To provide a patient their right amount of medication, therapeutic drug monitoring (TDM) is implemented in hospitals, because every patient responds differently to a certain dose of medication.
VPA is a conventional drug that is used as first line monotherapy for idiopathic generalized epilepsies. Its effectiveness is not clearly conclusive and varies between different patients. The doses are not generalized and depend on patient’s age and weight. Doses are taken every day, with some patients even two times a day. It is not advised, but sometimes necessary, to take VPA in combination with other seizure drugs (e.g., ethosuximide, lamotrigine, phenytoin, rufinamide, topira mate), some antidepressants or certain antibiotics<ref name=”[20]”> Valproic Acid (2018, October 1) , at [https://labtestsonline.org/tests/valproic-acid“https://labtestsonline.org/tests/valproic-acid”].</ref>. Medications based on VPA are harmful for the unborn child. If valproate is taken during pregnancy, research has shown that up to 4 in 10 babies are at risk of developmental disorders, and approximately 1 in 10 are at risk of birth defects. <ref name=”[22]”> gov.uk. (2018, March 23), at [https://www.gov.uk/guidance/valproate-use-by-women-and-girls“https://www.gov.uk/guidance/valproate-use-by-women-and-girls”].</ref>
==Safety & Lab protocols==
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To measure unbound VPA, blood samples are treated by ultrafiltration, followed by an immunoassay, also referred to as ELISA. By performing the ultrafiltration, the protein-bound form of VPA is separated from its unbound form. After that, the level of the unbound fraction can be measured by an immunoassay, e.g. an ELISA kit. Alternatively, LC-MS can be used to measure VPA.<ref name=”[40]”> ao, S., Miao, H., Tao, X., Jiang, B., Xiao, Y., Cai, F., … Chen, W. (2011, July 1). LC–MS/MS method for simultaneous determination of valproic acid and major metabolites in human plasma, Journal of Chromatography B
Volume 879, Retrieved November 28, 2019, at [https://www.sciencedirect.com/science/article/pii/S1570023211003278?via=ihub“https://www.sciencedirect.com/science/article/pii/S1570023211003278?via=ihub”].</ref>
. CMIA is a special type of ELISA <ref name=”[34]”> Ilyas M., Ahmad. I (2014, July 12), Chemiluminescent microparticle immunoassay based detection and prevalence of HCV infection in district Peshawar Pakistan, third alinea Background, Retrieved from November 7, 2019, at [https://virologyj.biomedcentral.com/articles/10.1186/1743-422X-11-127“https://virologyj.biomedcentral.com/articles/10.1186/1743-422X-11-127”].</ref>
.
Several innovations are being investigated for VPA testing. For example, 2D-LC system (two-dimensional chromatography) was studied, allowing large volume injection, reducing interfering components, and reducing the analysis time and preventing most interference components by selecting useful sections in the “heart-cut” column(1D) from entering the analysis column (2D).<ref name=”[11]”> Liu, W., Shang, X., Yao, S., & Wang, F. (2019, August 20). A novel and nonderivatization method for the determination of valproic acid in human serum by two‐dimensional liquid chromatography. Retrieved October 17, 2019, at [https://doi.org/10.1002/bmc.4695.“https://doi.org/10.1002/bmc.4695.”].</ref>
. Another example is dried blood spot (DBS) followed by gas chromatography mass spectrometry (GC–MS), which does not require solvent extraction or elution. The limit of quantitation was 200 ng/mL. <ref name=”[12]”> Guo, M., Shao, L., Chen, X., Li, H., Wang, L., Pan, Y., & Tang, D. (2019, September 13). Assay of dried blood spot from finger prick for sodium valproate via ink auxiliary headspace gas chromatography mass spectrometry, Journal of Chromatography A Vol. 1601 p. 335-339. Retrieved October 24, 2019, at [ https://doi.org/10.1016/j.chroma.2019.05.039“ https://doi.org/10.1016/j.chroma.2019.05.039”].</ref>
== References ==
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