Historical Intravenous Data Made CBD Bioavailability Estimates Approximate
The reported absolute bioavailability of a hemp cosmetic product was estimated using intravenous data from earlier research. It was not measured against an intravenous arm in the same participants.
The calculation crossed study boundaries
The paper reports estimated oral and topical CBD bioavailability of 10.18% and 0.69%. Its calculation combined route-specific exposure with previously published intravenous pharmacokinetic data. The current crossover compared oral and topical administration; it did not include an intravenous CBD treatment.
The reference data introduce uncertainty
Absolute bioavailability calculations depend on the reference exposure as well as the tested dose and route. The authors identify differences in populations, formulation, sampling duration and analytical methods as possible sources of variability when historical intravenous data are used. The numerical precision of the percentages does not remove those differences.
Observed exposure supports a narrower comparison
The trial’s measured concentration profiles supported greater systemic CBD exposure after oral administration than after application of this cosmetic oil. That within-study observation is different from establishing an exact fraction entering the circulation. The authors characterize the absolute estimates as approximate and hypothesis-generating. They should not be used as precise conversion factors between a person’s topical and oral doses, nor extended to other products without relevant data. Retaining the distinction between directly observed exposure and a historical-reference calculation makes the finding more useful rather than discarding it.
Related analysis: interpreting the study’s urine and plasma findings.
Research cited
Jain and colleagues. Results of an Exploratory Crossover Pharmacokinetic Study Evaluating a Natural Hemp Extract-Based Cosmetic Product: Comparison of Topical and Oral Routes of Administration. Pharmaceuticals (2026). DOI: 10.3390/ph19020231.
