Clinical Context
A patient treated for epilepsy presents for routine therapeutic drug monitoring while taking zonisamide to ensure serum concentrations remain within the therapeutic range and to assess adherence or toxicity. The patient may be seen in an outpatient neurology clinic, an ambulatory infusion center, or a hospital ward when inpatient management requires monitoring. A phlebotomy technician draws a blood specimen, which is labeled and sent to the clinical laboratory. The laboratory performs a quantitative assay for zonisamide (therapeutic drug monitoring). Results are reported to the ordering neurologist or primary care provider, who documents the level in the medical record and adjusts medication dose if indicated. Typical encounters include medication initiation, dose adjustment for seizure control, evaluation of suspected adverse effects (dizziness, rash, cognitive changes), or adherence checks during pregnancy or polypharmacy management.
Related CPT Codes
| CPT Code | Description | Relationship to This Procedure |
|---|
80203 | Zonisamide; assay of patient specimen | Primary code for the quantitative measurement of zonisamide levels |
36415 | Collection of venous blood by venipuncture | Often performed immediately prior to sending the specimen for the zonisamide assay
81025 | Urinalysis, reagent strip; multiple parameter, with microscopy if performed | May be performed concurrently for clinical assessment of adverse effects or metabolic evaluation
80307 | Drug screen, qualitative; multiple drug classes | May be ordered alongside zonisamide level to assess polypharmacy or concomitant substance use
80305 | Drug screen, qualitative; single drug class method | Alternative or adjunct when a specific concomitant drug is suspected
80053 | Comprehensive metabolic panel | Frequently ordered with therapeutic drug levels to assess renal and hepatic function relevant to zonisamide dosing