11-Hydroxy-THC Differences Between Capillary and Venous Blood Changed Direction Over Time
The active THC metabolite did not maintain one capillary-to-venous relationship after inhalation. Differences varied by sampling time and use group in the paired-blood study.
Early flower-user samples favored capillary concentrations
At ten minutes, 11-hydroxy-THC was significantly higher in capillary than venous samples among daily and occasional flower users. The corresponding early comparisons in daily concentrate users were nonsignificant. These findings did not follow the simple parent-THC pattern of generally lower capillary concentrations.
Later observations could reverse the comparison
Among daily concentrate users, capillary concentrations were significantly lower at 60, 90 and 140 minutes. Daily flower users also showed a later lower capillary comparison at 90 minutes. At 140 minutes, the flower-user groups did not show a significant difference.
A fixed correction would discard the temporal pattern
The study involved upper-arm capillary collection and a modified processing workflow in 29 people. Its results do not supply a universal conversion for another site or device. The comparatively low metabolite concentrations also limited power for some comparisons. Preserve both significant and null results and the actual elapsed time, rather than applying the parent compound’s direction or a single ratio to this active metabolite.
Related analysis: the study’s broader findings and limitations.
