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Homogeneous Immunoassays—Therapeutic Drug Monitoring
QMS®—Latex Enhanced Immunoturbidimetric Assays
Valproic Acid Assay System
The VALPROIC ACID Assay System is intended for the quantitative determination of total valproic acid in serum for therapeutic drug monitoring.
Valproic acid is a branched short-chain fatty acid which, unlike other anticonvulsants, lacks a nitrogen and aromatic ring moiety.1,2 It is indicated for use alone and in combination therapy for various types of seizures.2,3 The drug is widely used in children and is considered the drug of first choice in Europe for all primary generalized epilepsies.1,4
Valproic acid is rapidly absorbed following oral administration, with peak serum levels occurring 1-4 hours after a single dose.1,2 Valproic acid is eliminated primarily in urine. Elimination half-lives range from 10-16 hours for monotherapy and 8-10 hours when administered with other anticonvulsants.1 The drug is over 90% bound to plasma proteins, primarily albumin, at serum concentrations of 50-80ug/ml. Above 80-90ug/ml, the free fraction increases with variable effects on clearance and elimination.1-3 Metabolism of valproic acid occurs in the liver and the drug is excreted as glucuronide conjugates as well as products of beta and omega oxidation.1-3 The mechanism of the drug’s antiepileptic affects has not been established, but appears to be related to changes in membrane conductance and gamma-aminobutyric aced (GABA) levels in the brain.5
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