Levetiracetam

This assay tests for levetiracetam, an anticonvulsant medication used to control certain types of seizures in patients with epilepsy.  Levetiracetam is a prescribed drug that helps prevent partial onset or focal, myoclonic, and tonic-clonic seizures.

It is marketed under the trade names Keppra^® and Keppra XR^® (extended release). It is an effective seizure drug because it has a wider therapeutic range than many existing first-generation seizure medications. It is also associated with fewer severe adverse effects and does not interact with as many other drugs. Common adverse effects include weakness, infection, and drowsiness.¹ Some symptoms of toxicity include extreme drowsiness, agitation, aggression, hallucinations, lack of coordination, rash, and numbness, tingling, or burning in the hands or feet.¹

The laboratory test is a quantitative assay that reports measured serum levels of levetiracetam in mcg/mL. Levetiracetam serum level testing is important because it can help verify and optimize desired dosage for the patient, verify patient adherence to prescription criteria, detect occurrence of toxicity from overdose, and help monitor the impact of recent health changes that affect drug clearance or kidney function.

Once steady state has been reached, blood specimens can be collected 0.5 to 1 hour before the next oral dose (trough).

Note: After onset of treatment, steady state is typically reached in 2 days for adults and in 1 to 2 days for children. The elimination half-life is 6 to 8 hours in adults with epilepsy, 5 to 7 hours in children with epilepsy, and 10 to 11 hours in elderly volunteers.²

The therapeutic range of levetiracetam is generally 10.0 to 40.0 mcg/mL (mg/L) for trough collections.^3, A trough blood concentration >46 µg/mL may be toxic; however, toxic levels are not well established.⁴ Results should be interpreted in the context of the clinical picture, including evidence of drug effectiveness and/or toxicity.

Most people with blood levels within the therapeutic range will respond to the drug without excessive adverse effects. However, individual responses can vary,  and some patients may require dosages outside of the established range to effectively control seizures and/or limit adverse effects. Dosage is considered adequate if the patient has no recurrent seizures and no significant adverse effects.

A levetiracetam concentration above or below the therapeutic range may indicate that the patient is not taking the drug as prescribed. Additionally, high concentrations may be a sign of impaired renal function, if the drug is not optimally cleared through the kidneys.