Pharmaceutical CBD Produced Zero Detectable THC in Children's Blood Over 5 Years
Long-term plasma monitoring of 38 children on Epidyolex for drug-resistant epilepsy confirmed that THC remained consistently undetectable while CBD levels rose predictably with dose.
Quick Facts
What This Study Found
THC was undetectable (<0.2 mcg/L) at all timepoints across all 38 patients throughout the study period (2019-2024). CBD plasma levels increased dose-dependently, reaching a median of 89.8 mcg/L at final follow-up, with a significant correlation between dose and concentration (p < 0.0001). Mean CBD dose was 13.6 mg/kg/day.
Key Numbers
THC undetectable (<0.2 mcg/L) at all timepoints; 38 patients; median age 11 years; mean CBD dose 13.6 mg/kg/day; median CBD level 89.8 mcg/L at final follow-up; significant dose-concentration correlation (p < 0.0001); 2019-2024 monitoring period
How They Did This
Retrospective analysis of 38 pediatric patients (median age 11 years) treated with Epidyolex at a single center from 2019 to 2024. Plasma CBD and THC measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS).
Why This Research Matters
Parents of children on CBD therapy often worry about THC exposure. This long-term monitoring data provides strong reassurance that pharmaceutical-grade CBD (Epidyolex) produces no detectable THC in the blood, even over years of use, while confirming that dose adjustments reliably change CBD levels.
The Bigger Picture
As CBD-based therapies expand, confirming long-term safety data like zero THC exposure is essential for both regulatory confidence and parental peace of mind. This study supports the case for therapeutic drug monitoring to optimize individual dosing.
What This Study Doesn't Tell Us
Single center, retrospective design, only pharmaceutical-grade CBD studied (non-pharmaceutical products may differ), no clinical outcome data in this specific analysis, cannot generalize to adult patients
Questions This Raises
- ?Do non-pharmaceutical CBD products produce similar zero-THC profiles?
- ?Would therapeutic drug monitoring improve seizure outcomes?
- ?Should plasma CBD monitoring become standard clinical practice?
Trust & Context
- Key Stat:
- THC was undetectable at every measurement in all 38 children over 5 years of CBD therapy
- Evidence Grade:
- Moderate-sized retrospective monitoring study with objective laboratory measurements; strong pharmacokinetic data from a single center
- Study Age:
- Published 2025
- Original Title:
- Long-term plasma monitoring of THC and CBD in pediatric drug-resistant epilepsy: Implications for cannabidiol therapy with Epidyolex®.
- Published In:
- Epilepsia open, 10(5), 1699-1704 (2025)
- Authors:
- Cafaro, Alessia(2), Riva, Antonella(4), Pigliasco, Federica(2), Barco, Sebastiano, Manca, Valentina, Stella Vari, Maria, Mancardi, Maria Margherita, Nobili, Lino, Pichini, Simona, Busardò, Francesco Paolo, Striano, Pasquale, Cangemi, Giuliana
- Database ID:
- RTHC-06141
Evidence Hierarchy
Looks back at existing records to find patterns.
What do these levels mean? →Frequently Asked Questions
Does pharmaceutical CBD contain THC?
Epidyolex is a highly purified CBD formulation. In this study of 38 children monitored for up to 5 years, THC was never detected in their blood at any measurement point, confirming negligible THC exposure.
Do CBD blood levels change predictably with dose?
Yes. CBD plasma levels increased in direct proportion to the dose, with a highly significant correlation (p < 0.0001), supporting the use of blood monitoring to guide individualized dosing.
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Cite This Study
https://rethinkthc.com/research/RTHC-06141APA
Cafaro, Alessia; Riva, Antonella; Pigliasco, Federica; Barco, Sebastiano; Manca, Valentina; Stella Vari, Maria; Mancardi, Maria Margherita; Nobili, Lino; Pichini, Simona; Busardò, Francesco Paolo; Striano, Pasquale; Cangemi, Giuliana. (2025). Long-term plasma monitoring of THC and CBD in pediatric drug-resistant epilepsy: Implications for cannabidiol therapy with Epidyolex®.. Epilepsia open, 10(5), 1699-1704. https://doi.org/10.1002/epi4.70112
MLA
Cafaro, Alessia, et al. "Long-term plasma monitoring of THC and CBD in pediatric drug-resistant epilepsy: Implications for cannabidiol therapy with Epidyolex®.." Epilepsia open, 2025. https://doi.org/10.1002/epi4.70112
RethinkTHC
RethinkTHC Research Database. "Long-term plasma monitoring of THC and CBD in pediatric drug..." RTHC-06141. Retrieved from https://rethinkthc.com/research/cafaro-2025-longterm-plasma-monitoring-of
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.