Valporic acid

This test measures the amount of valproic acid in the blood. Valproic acid is a drug that is used mainly to treat certain fitting disorders (also called seizures or epilepsy), but is also prescribed to treat bipolar disease (manic depression) and to prevent migraine headaches, though this is an unlicensed use of valproic acid in the UK. It may be used in combination with other antiepileptic drugs such as phenytoin or carbamazepine 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 fits. Seizures can occur with rapidly developing conditions, such as high fevers, head trauma, severe infections, and exposure to toxins, and with long-term diseases such as metabolic disorders and brain tumours. In many cases, the cause is not known. The frequency of seizures varies from a single episode, to occasional, or frequent seizures. Rarely, a patient may have a seizure that does not stop without prompt medical treatment. People may experience some tiredness and a short period of confusion after a seizure. Muscles contract during a seizure and can lead to an injury and, in some cases, recurrent seizures can eventually lead to continuing 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 reduce the frequency and severity of seizures.

Bipolar disorder is a mental disease that has 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 behaviours. Valproic acid is prescribed to help even out the moods of the person with bipolar disorder, especially mania. It may also be given to some patients with recurrent migraine headaches, not to treat an acute attack but to help prevent attacks.

Valproic acid levels in the blood must be maintained within certain limits. Too little and the patient may have more symptoms (seizures, mood swings, or migraines); too much and the patient may have increased side effects. This balance is not always easily achieved. The drug is broken down by the liver, but the rate varies from patient to patient and is affected by a patient’s age and the health of their liver. In addition, valproic acid levels are often affected by other drugs such as carbamazepine, phenytoin, lamotrigine, and phenobarbital. These drugs increase the rate that valproic acid is broken down and therefore reduces its levels in the blood.

Monitoring of blood levels may be more important when someone is taking more than one drug.

The dose of valproic acid must be adjusted until a suitable concentration in the blood is reached. The amount of drug that is required to reach a steady state will vary from person to person and may change over time. Measuring the valproate level in the blood may help in this process in some cases, but is not often necessary.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.