Undetectable Plasma THC During Pediatric CBD Treatment Had a Defined Limit
THC was not detected in 103 plasma samples from children receiving highly purified CBD in a retrospective study. The finding supports a narrow analytical conclusion about the sampled treatment regimen; it does not establish that every CBD product contains no THC or that all safety questions are settled.
Samples were repeated observations
The cohort comprised 38 children with drug-resistant epilepsy, with a median age of 11 years. Investigators reviewed routine predose CBD and THC measurements obtained between 2019 and 2024 during adjunctive Epidyolex treatment.
The 103 specimens were not 103 independent children. Follow-up and dose varied between patients, and the median follow-up duration was 17 months. This was a single-center observational analysis rather than a randomized comparison of product types.
What ‘undetectable’ meant
Plasma THC remained below 0.2 micrograms per liter across the measured time points. CBD concentrations increased with prescribed dose, and the final-follow-up median CBD concentration was 89.8 micrograms per liter.
A result below an analytical limit is not a measurement of absolute zero. Predose sampling also addresses a particular part of the dosing interval, rather than documenting every possible transient concentration after administration.
Product and outcome boundaries matter
The report concerns a highly purified prescribed preparation. It does not guarantee identical findings for retail oils, full-spectrum extracts, mislabeled products or different dosing schedules. Plasma results also cannot automatically predict a urine-screen outcome.
An association between dose and CBD concentration does not independently demonstrate seizure efficacy, optimal dosing or absence of drug interactions. The useful conclusion is that this cohort’s repeated predose samples showed CBD exposure without quantifiable THC under the specified method, population and treatment conditions.
Related: Why cannabinoid concentration and impairment require separate interpretation.
Primary research
Long‐term plasma monitoring of THC and CBD in pediatric drug‐resistant epilepsy: Implications for cannabidiol therapy with Epidyolex®. Epilepsia Open (2025).
