When an exposure is repeated, the most recent dose tells only part of the story. Corsato Alvarenga and colleagues studied healthy adult dogs given CBD oil daily over 36 weeks. They conducted pharmacokinetic sampling at baseline and again at weeks 18 and 36.
Exposure rose over the course of the study
At the later assessments the investigators reported higher peak plasma concentrations and larger areas under the concentration–time curve. The area under the curve summarizes measured exposure over time. The authors also reported a longer estimated half-life at the later assessments and substantial variation in half-life among dogs.
The results show why duration of administration belongs in an exposure history. Comparing a value from chronic use with a first-dose study can omit an important difference in conditions. The observed changes were specific to the dogs, doses and oil studied. A different species, formulation or dosing history would require its own supporting data.
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