An Unreached Rimonabant ED50 Limited the Precision of a THC-Adaptation Comparison
When an experiment does not reach the response needed to estimate an ED50, the largest tested dose is not an ordinary measured ED50. A primate THC study preserved that distinction in its rimonabant analysis.
The baseline curve did not support the usual estimate
Before chronic THC, rimonabant did not reduce responding below half of control across the relevant testing conditions. McMahon therefore used the largest tested dose as a conservative baseline estimate rather than reporting it as a fully determined midpoint.
A descriptive shift lacked a conventional interval
During chronic THC, smaller rimonabant doses produced stronger response suppression. The paper described increased sensitivity but stated that the potency-ratio confidence limits could not be calculated in the usual way. It also reported different dose-response significance results for the two behavioral components.
A number needs its estimation method
A precise-looking fold comparison should not conceal an incomplete baseline curve. The observation can support altered sensitivity while leaving its magnitude and statistical precision less fully resolved than other drug comparisons. This is an assay limitation in three monkeys, not a validated marker of human withdrawal severity. Retaining the estimation caveat prevents a substituted dose bound from being mistaken for a directly measured biological threshold.
Related: Interpreting cannabinoid tolerance evidence.
Research cited
Lance R. McMahon. Chronic Δ9-tetrahydrocannabinol treatment in rhesus monkeys: differential tolerance and cross-tolerance among cannabinoids (2011).
