Clinical value and significance of determining valproic acid in blood serum.

Neurologist of the highest category, epileptologist at the VITAMED MEDICAL clinic, Luiza Usmanovna Khusanbaeva, will introduce you to an article on the topic: “Clinical value and significance of determining valproic acid in blood serum.”

 

Valproic acid is an anticonvulsant drug widely used to treat various types of epilepsy in adults and children.

Synonyms: Depakin, Konvulex.

Drug monitoring – a method of monitoring and monitoring the distribution of drugs introduced into the body by determining their concentration in the blood.

The importance of monitoring is to timely and correctly control the level of anticonvulsant drugs in the blood in order to achieve complete control of the disease and help the patient.

Valproic acid inhibits the enzyme GABA transferase and, as a result, increases the content of the inhibitory neurotransmitter - gamma-aminobutyric acid (GABA) - in the nervous system.

Valproic acid preparations are quickly and almost completely absorbed from the gastrointestinal tract, reaching maximum concentrations in the blood after 1.5-4 hours. Moreover, they are characterized by nonlinear (dose-dependent) pharmacokinetics, when the concentration of the drug in the blood increases or decreases faster than the increased or decreased dose. If the upper limit of their average therapeutic level is exceeded, the greater likelihood of side effects, in some cases even intoxication, must be taken into account.

Valproic acid is primarily metabolized in the liver and may cause liver damage, especially during the first 6 months after starting treatment. Therefore, before therapy with valproic acid, each patient must undergo a series of tests to study liver function.

The basis for calculating the dose of Valproate is the patient's weight, but scientists have found that even in people with the same weight, the active concentration of the drug in the blood differs significantly. This is explained by the individual characteristics of drug metabolism. Therefore, for better treatment, doctors focus on the content of the drug in the blood.

 

 Indications for determining concentration:

• When prescribing the drug for the first time - if the patient has never taken AEDs (anti-epileptic drugs), after its administration, a content analysis is required after reaching a stable concentration (minimum equal to five half-lives)
•  1-2 times a year when control of attacks is achieved and positive dynamics of the disease as a whole 
•  In young children due to rapidly changing body weight, once every 3 months
• In pregnant and lactating women due to altered metabolism, once every 3 months
• When prescribing multiple anticonvulsant drugs (drug interactions) or discontinuing other drugs taken concomitantly with AEDs
•  If there is any deterioration in the condition of a patient taking an anticonvulsant
• If there is any doubt about the correctness and correctness of the patient taking the drug

Research method - Immunochemiluminescent analysis.

Units of measurement are mcg/ml (micrograms per milliliter).

Reference values: 50 - 100 µg/ml.

For analysis, 0.5–1 ml of venous blood is taken. Blood for analysis is taken twice (this is a standard technique): 1st sample - immediately before the patient takes the medicine (residual concentration after the last dose), 2nd sample - 2-3 hours after administration (reaching the maximum concentration in the blood). At the same time, the procedure for drawing blood is determined by the attending physician and may differ significantly from the standard technique.

 The timing of blood sampling varies depending on the clinical situation. If the indication for the study is the ineffectiveness of therapy or suspected drug interactions, then a blood sample is obtained immediately before taking a dose of the drug. When testing for toxic effects, blood is drawn at the time of onset of symptoms or the expected peak concentration if symptoms have not fluctuated.

 Reasons for increased valproic acid levels:

• excess dosage and/or incorrect administration of valproic acid drugs;
• acute poisoning with valproic acid drugs.

Reasons for decreased valproic acid levels:

• removal of valproic acid drugs from the body.

Thus, we can state that determining the level of anticonvulsants in the blood can provide the doctor with valuable information for making treatment decisions.

The dose-concentration-effect relationship does not appear to be linear. Each patient has an individual therapeutic range, which may differ significantly from the standard.

 Without a clinical understanding of the patient’s condition, without a correct assessment of the neurological status, without data from neurophysiological (electroencephalography) and neuroimaging (MRI, MSCT) research methods, monitoring of anticonvulsants will not be meaningful. As well as the above methods without drug monitoring.

 

Be healthy and take care of your loved ones!

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