Why the Same THC Spray Dose Produced Different Concentrations in Older Patients
The same prescribed THC/CBD spray regimen did not produce a uniform concentration-time profile in older patients. Population modeling found substantial variation both between patients and between doses in the same patient.
The observed population and regimen
Storgaard and colleagues studied 20 older medical patients with poor appetite. Participants received fixed doses of a THC/CBD oromucosal spray, separated by four hours, with blood sampling over a limited study day. The investigators modeled THC and its active 11-hydroxy metabolite.
The paper refers to plasma concentrations in places, while its sample-processing methods describe coagulation and serum handling. That terminology needs clarification before any value is compared with another laboratory matrix. These results should not be relabeled as whole-blood measurements.
Variability was not explained away
The models identified large interindividual and intraindividual variability. The tested clinical covariates did not show clinically significant effects that explained the pharmacokinetic variation. That null covariate finding matters: the paper does not validate a simple body-composition or renal-function adjustment that predicts every person’s concentration.
Oromucosal dosing can involve variable mucosal absorption and swallowing, but an explanatory model is not a direct measurement of each absorption pathway in every patient.
The terminal phase was not captured
Sampling ended only a few hours after the final dose. The authors explain that the terminal elimination phase was not characterized. Model parameters therefore should not be treated as a complete account of long-term elimination or accumulation during continued treatment.
A best-fitting compartment model describes the available data under its assumptions. It does not establish a universal biological clock or make an individual’s earlier dose uniquely recoverable from one later concentration.
Implications for expert interpretation
Obtain the actual dose times, administration technique, food history, specimen matrix, collection times, and assay details. Distinguish measured observations from model-derived parameters and prediction intervals.
The study concerns pharmacokinetics in a specific older clinical population, not a validated impairment threshold. Its practical lesson is that identical prescribed doses can yield different measured exposures, while neither dose nor concentration alone establishes an individual’s functional state.
For related context, see our discussion of how edible and vaporized cannabis differ in timing.
Primary research
Ida Klitzing Storgaard; Rikke Lundsgaard Nielsen; Morten Baltzer Houlind; Olivia Bornæs; Louise Westberg Strejby Christensen; Aino Leegaard Andersen; Helle Gybel Juul‐Larsen; Lillian Mørch Jørgensen; Torben Breindahl; Baker Nawfal Jawad; Izzet Altintas; Ove Andersen; Trine Meldgaard Lund. Population pharmacokinetic modelling revealed large variability in oromucosal absorption of Δ9‐tetrahydrocannabinol in older patients with poor appetite. British Journal of Clinical Pharmacology (2025). DOI: 10.1002/bcp.70284.
