At a Glance
Why Get Tested?
To determine the concentration of valproic acid in the blood and to maintain a therapeutic level
When to Get Tested?
At regular intervals to monitor the drug's level; to detect low or excessive (potentially toxic) concentrations
A blood sample drawn from a vein in your arm
Test Preparation Needed?
No special test preparation needed, but talk to your doctor about the timing of sample collection. Since dosage timing varies and some formulations are time-released, collection specifics may vary. Often, the recommended time for sample collection is just before the next dose is taken (trough level).
The Test Sample
What is being tested?
This test measures the level of valproic acid in the blood. Valproic acid is a drug that is used primarily to treat certain seizure disorders (also called epilepsy), but is also prescribed to treat bipolar disease and to prevent migraine headaches. It may be prescribed in combination with other antiepileptic drugs such as phenytoin or phenobarbital to control certain kinds of seizures.
Seizure disorders affect the brain's ability to transmit electrical impulses and to regulate nerve activity. During a seizure, a patient may experience changes in consciousness, alterations in sight, smell, and taste, and may experience convulsions. Seizures are associated with acute conditions, such as high fevers, head trauma, severe infections, and exposure to toxins, and with chronic conditions such as metabolic disorders and brain tumors. In many cases, the cause is not known. The frequency of seizures varies from a single episode, to occasional seizures, to recurrent. Rarely, a patient may have a seizure that does not stop without prompt medical intervention. People may experience some fatigue and a short period of confusion after a seizure. Muscle contractions during a seizure can lead to an injury and, in some cases, recurrent seizures can eventually lead to progressive brain damage, but for most people there will be little or no residual damage. Anti-seizure medications such as valproic acid may be prescribed to lessen the frequency and severity of seizures.
Bipolar disorder is a mental condition that is characterized by cycles of depression and mania that may last for days, weeks, months, or years. During a depressive episode, those affected may feel sad, hopeless, worthless, and have thoughts of suicide. During a manic episode, those affected may be euphoric, irritable, use poor judgment, and participate in risky behaviors. Valproic acid is prescribed to help even out the moods of the person with bipolar disorder, especially mania. It is also given to some patients with recurrent migraine headaches, not so much to treat migraines as to help prevent their occurrence.
The valproic acid level must be maintained within a narrow therapeutic range. Too little drug and the patient may experience a recurrence of symptoms (seizures, mania, or migraines); too much drug and the patient may experience an increase in the number and severity of side effects. This balance is not always easily achieved. The drug is metabolized by the liver and is processed at a rate that varies from patient to patient and is affected by a patient's age and the health of their liver. In addition, valproic acid can interact with other drugs such as carbamazepine, phenytoin, lamotrigine, and phenobarbital, so monitoring of blood levels may be especially important when someone is taking more than one drug. Furthermore, most valproic acid is bound to protein in the blood and it is the unbound "free" portion that is active. If someone has a condition that results in a lower than normal amount of protein in their blood, then that person may have an excess of active valproic acid.
Dosages of valproic acid must be adjusted carefully until a steady concentration in the blood is reached. The actual amount of drug that it takes to reach this steady state will vary from person to person and may change over time.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No special test preparation is needed, but patients should talk to their doctor about the timing of the sample collection. Since dosage timing varies and some formulations are time-released, collection specifics may vary. Often, the recommended time for sample collection is just before the next dose is taken (trough level). This ensures that the minimum amount of drug to be effective is maintained in the blood.
Ask a Laboratory Scientist
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL eds, (2005) Harrison's Principles of Internal Medicine, 16th Edition, McGraw Hill, Pp 2366-2368.
(October 10, 2009) American Cancer Society. Valproic Acid. Available online at http://www.cancer.org/Treatment/TreatmentsandSideEffects/GuidetoCancerDrugs/VALPROIC-ACID through http://www.cancer.org. Accessed January 2011.
Kidshealth. Blood test: Valproic Acid. Available online at http://kidshealth.org/parent/system/medical/test_valproic.html through http://kidshealth.org. Accessed January 2011.
(Updated November 4, 2010) Weigand T. Toxicity, Valproate. eMedicine online article. Available online at http://emedicine.medscape.com/article/819315-overview through http://emedicine.medscape.com. Accessed January 2011.
(June 28, 2010) McCall B. Valproate Carries Highest Risk for Major Congenital Malformations of All Anitepilieptics. Medscape Medical News. Available online at http://www.medscape.com/viewarticle/724671 through http://www.medscape.com. Accessed January 2011.
(December 3, 2009) Hitt E. FDA Reminds Healthcare Professionals of Valproate Link to Birth Defects. Medscape Medical News. Available online at http://www.medscape.com/viewarticle/713380 through http://www.medscape.com. Accessed January 2011.
Mayo Medical Laboratories. Valproic Acid, Free and Total, Serum. Available online at http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/81771 through http://www.mayomedicallaboratories.com. Accessed January 2011.
ARUP Laboratories. Valproic Acid, Free and Total. Available online at http://www.aruplab.com/guides/ug/tests/0099310.jsp through http://www.aruplab.com. Accessed January 2011.
(March 4, 2010) Glauser T. Ethosuxamide, Valproic Acid and Lamotrigine in Childhood Absence Epilepsy. N Engl J Med 2010; 362:790-799. Available online at http://www.nejm.org/doi/full/10.1056/NEJMoa0902014#t=articleTop through http://www.nejm.org. Accessed January 2011.
Narayanaswamy, Sudha (November 2010). Depakote (vivalproex sodium) – Valproic Acid. National Alliance on Mental Illness. Available online at http://www.nami.org/Template.cfm?Section=About_Medications&Template=/TaggedPage/TaggedPageDisplay.cfm&TPLID=51&ContentID=20823 through http://www.nami.org. Accessed January 2011.
(December 14 2010, Updated). Seizures and Epilepsy: Hope Through Research. NINDS [On-line information]. Available online at http://www.ninds.nih.gov/disorders/epilepsy/detail_epilepsy.htm through http://www.ninds.nih.gov. Accessed January 2011.
Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
(© 2007). Valproic Acid. Epilepsy.com [On-line information]. Available online at http://www.epilepsy.com/medications/b_valproicacid_intro.html through http://www.epilepsy.com. Accessed on 4/1/07.
Waknine, Y. (2007 February 7). FDA Safety Changes: Kenalog-10 and Kanalog-40, Depacon, Depakene [On-line information]. Available online at http://www.medscape.com/viewarticle/551786 through http://www.medscape.com/viewarticle/551786. Accessed on 3/25/07.
Macritchie, KA (2006 October 1). Valproic acid, valproate and divalproex in the maintenance treatment of bipolar disorder. Medscape from Cochrane Rev Abstract [On-line information]. Available online at http://www.medscape.com/viewarticle/486474 through http://www.medscape.com. Accessed on 3/25/07.
Narayanaswamy, Sudha (2005 August, Updated). Depakote (vivalproex sodium) - Valproic Acid. NAMI [On-line information]. Available online through http://www.nami.org. Accessed on 3/25/07.
(2005 September). Depakene/Depakote/Depakote ER. Epilepsy Foundation [On-line information]. Available online at http://www.epilepsyfoundation.org/answerplace/Medical/treatment/medications/typesmedicine/depakote.cfm through http://www.epilepsyfoundation.org. Accessed on 3/31/07.
(2007 March 1). Valproic Acid (Oral Route, Parenteral Route). MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/drug-information/DR602153 through http://www.mayoclinic.com. Accessed on 3/25/07.
(2005 August 10, Review). Seizures Emergencies Overview. eMedicineHealth [On-line information]. Available online at http://www.emedicinehealth.com/seizures_emergencies/article_em.htm through http://www.emedicinehealth.com. Accessed on 3/31/07.
(2006 October). Valproic Acid - Drug Review. Consumer Reports Medical Guide [On-line information]. Available online at http://www.consumerreports.org/mg/drug-reports/valproic-acid.htm through http://www.consumerreports.org. Accessed on 3/31/07.
(2004 April, Revision). Valproate, valproic acid, divalproex sodium. American Epilepsy Society [On-line information]. Available online at http://www.aesnet.org/Visitors/PatientsPractice/aed/aedtable.cfm?drug=Valproate%2C%20valproic%20acid%2C%20divalproex%20sodium through http://www.aesnet.org. Accessed on 4/1/07.
(2007 March 19, Updated). Seizures and Epilepsy: Hope Through Research. NINDS [On-line information]. Available online at http://www.ninds.nih.gov/disorders/epilepsy/detail_epilepsy.htm through http://www.ninds.nih.gov. Accessed on 3/31/07.
Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry. AACC Press, Washington, DC. Harris, N. et. al. Chapter 39: Therapeutic Drug Monitoring. Pg 461.
Burtis C, Ashwood E, Bruns D, Eds. (2006). Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier Saunders, St. Louis, Missouri. Pp 1253-1254.