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Levetiracetam

Test code(s) 15142

Question 1. What does this assay test for?

This assay tests for levetiracetam, an anticonvulsant medication used to control certain types of seizures in patients with epilepsy.

Levetiracetam is prescribed to help prevent partial onset, myoclonic, and tonic-clonic seizures and is marketed under the trade names Keppra® and Keppra XR® (extended release). It has a wider therapeutic range than many existing first-generation seizure medications. It is 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

Question 2. What is the purpose of levetiracetam testing?

Levetiracetam testing can help optimize dosage, verify adherence, detect toxicity, and monitor the impact of a recent health change affecting drug clearance or kidney function.

Question 3. When should specimens be collected for levetiracetam testing?

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

Note: steady state is typically reached 2 weeks after onset of treatment. 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.

Question 4. How are test results interpreted?

The therapeutic range of levetiracetam is generally 12 to 46 µg/mL (mg/L) for trough collections. A trough blood concentration >46 µg/mL may be toxic; however, toxic levels are not well established.2 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. Individual responses can vary, however, 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, as the drug is cleared through the kidneys.

Reference

  1. Keppra® [package insert]. Smyrna, GA: UCB, Inc; 2009. http://www.accessdata.fda.gov/drugsatfda_docs/label/2009/021035s078s080,021505s021s024lbl.pdf
  2. Patsalos PN. Clinical pharmacokinetics of levetiracetam. Clin Pharmacokinet. 2004;43:707-724.
This FAQ is provided for informational purposes only and is not intended as medical advice. A clinician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.
Document FAQS.180 Version: 1
Version 1: Effective 10/08/2019 to present
Version 0: Effective 10/26/2016 to 10/08/2019