A question about intended drug use and an opportunity to take the drug are different measures. A medication can change an answer on a rating scale without changing behavior in the laboratory task used to assess drug taking.
The participants and the actual choices
De La Garza and colleagues’ 2012 double-blind crossover experiment enrolled 20 adults with methamphetamine dependence who were not seeking treatment. Seventeen completed all conditions; excluding two methamphetamine nonresponders left 15 in the analysis. Oral rivastigmine conditions were 0, 3 or 6 mg/day, with treatment on days 2–8. Acute methamphetamine challenges were 15 and 30 mg intravenously.
Rivastigmine attenuated the peak “Likely to Use METH” rating (p=0.01), particularly with 6 mg rivastigmine and the 15-mg challenge. The peak desire result was nonsignificant (p=0.27). Rivastigmine did not reduce total methamphetamine choices in a separate task offering 5-mg intravenous infusions versus no infusion. No monetary alternative was offered.
A rating is not a validated substitute for drug taking
Calling the rating result reduced methamphetamine use would replace the measured outcome with a different one. The appropriate explanation keeps the words on the questionnaire visible and then reports the behavioral result separately.
That separation is more informative than declaring the whole experiment positive or negative. A subjective effect may help develop a hypothesis about how a medicine changes experience. The behavioral task asks whether that change carries into the specific opportunity to obtain drug. Neither outcome should erase the other.
The denominator also affects the inference. The final group excluded people who did not show the required acute methamphetamine response. A finding in that selected group cannot automatically describe everyone with methamphetamine dependence, including people who would not have met that response condition.
Why the alternative in a choice task matters
A decision between an infusion and no infusion is not the same decision as drug versus money, work, family commitments or another competing reward. The task defines what a choice costs and what can be obtained instead. Interpretation therefore requires the actual alternatives, rather than the phrase “self-administration” alone.
The null behavioral result does not establish that every possible rivastigmine regimen must fail. Conversely, the favorable rating does not demonstrate outpatient effectiveness. A treatment claim would need a suitable clinical comparison with outcomes that directly address the proposed benefit.
For an expert report, this study is useful as a concrete example of why intention, subjective drug effects and observed consumption require separate descriptions. It is historical human laboratory evidence, not a current recommendation to use rivastigmine for methamphetamine-related conditions.
Source
De La Garza R II, et al. Rivastigmine reduces “Likely to use methamphetamine” in methamphetamine-dependent volunteers. Prog Neuropsychopharmacol Biol Psychiatry. 2012;37:141–146. doi:10.1016/j.pnpbp.2011.12.014. Full text.