Valproic Acid, Total, Serum/Plasma

Valproic acid is a simple eight-carbon branched-chain fatty acid used in the treatment of various forms of epilepsy. Valproic acid is absorbed rapidly after oral dose, is metabolised largely by the liver and mainly eliminated in the urine, with minor amounts in the faeces and expired air. Elimination of Valproic acid is impaired in acute viral hepatitis and liver cirrhosis and enhanced in the presence of enzyme-inducing drugs. Concurrent administration of Valproic acid and Phenobarbital often increases the concentration of Phenobarbital. In addition, Valproic acid can displace phenytoin from plasma-protein binding sites. On the other hand, other drugs such as salicylates may displace or inhibit the metabolism of Valproic acid. One of the major adverse effects of Valproic acid is its potential hepatotoxicity.

Measurement of Valproic acid levels are performed to monitor and maintain the desired therapeutic drug concentration and avoid high toxic levels.

1 ml Serum 1 ml Li, Na-Heparin or K2, K3, Na2-EDTA Plasma Stability: 2 Days at Room Temperature 7 Days at 2-8 °C 3 Months at -20 °C

Sampling time for trough is immediately prior to administration of the next dose. Peak serum concentration for syrup is reached 30 min - 1 Hr after dose. For capsules peak is reached 30 min - 2 Hrs after dose. Avoid grossly haemolysed samples.

Therapeutic Range: 50 - 100 μg/mL 347 - 694 μmol/L Toxic: > 100 μg/mL > 694 μmol/L