Summary & Overview
CPT 80203: Zonisamide Level Testing
CPT code 80203 represents a laboratory assay to measure zonisamide levels in a patient’s specimen for therapeutic drug monitoring. This test supports clinical decision-making in patients receiving zonisamide by identifying subtherapeutic, therapeutic, or potentially toxic concentrations. Nationally, therapeutic drug monitoring codes like 80203 are important for medication safety programs, outpatient and inpatient care coordination, and payer coverage policies tied to epilepsy and seizure management.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the code’s clinical context, typical sites of service, and the role of zonisamide level testing in care pathways. The publication outlines common billing and reporting considerations, expected service settings (clinical and hospital laboratories), and where to find related coding guidance. Data not available in the input is noted where applicable.
Billing Code Overview
CPT code 80203 describes a laboratory test performed to determine the level of zonisamide, an antiepileptic medication, in a patient’s biological specimen. This service is a therapeutic drug monitoring assay used to assess medication concentration for clinical management.
Service Type: Laboratory therapeutic drug monitoring
Typical Site of Service: Clinical laboratory or hospital laboratory
Clinical & Coding Specifications
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.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
00 | Procedure or service furnished—no further specification | Rarely used; default when no other modifier applies |
11 | Professional component | When only the professional interpretation component is billed separately (rare for laboratory quantitative assays)
26 | Professional component | If a separate professional interpretation by a pathologist or laboratory physician is reported