People trained to recognize methamphetamine’s internal effects also responded similarly after d-amphetamine and methylphenidate. That laboratory finding demonstrates overlapping drug cues, not that the substances are chemically identical or interchangeable.
Sevak and colleagues first trained volunteers to distinguish 10 mg oral methamphetamine from placebo. The discrimination criterion required at least 80% drug-appropriate responding over four consecutive sessions. The researchers then tested several oral doses of methamphetamine, d-amphetamine, methylphenidate and triazolam.
This procedure measures whether a drug produces an internal cue similar to the trained cue. It is different from asking someone to identify an unknown specimen by chemical testing.
D-amphetamine and methylphenidate produced dose-related increases in methamphetamine-appropriate responding. Triazolam did not, instead producing sedative-like subjective effects. Methamphetamine produced significant increases in heart rate and blood pressure above placebo; the other tested drugs did not show the same significant cardiovascular comparisons.
No tested drug significantly changed performance on the Digit-Symbol Substitution Test. Thus, evidence of a recognized stimulant-like cue was not equivalent to a detectable change on that performance measure.
The discrimination result cannot establish which drug a person used outside the laboratory, whether a positive toxicology screen represents a particular compound, or whether a person was impaired. Those questions require different evidence. A behavioral response is not an analytical identification of an analyte.
The investigators emphasized the small sample, relatively low doses and oral route. Participants were not stimulant abusers, which limits application to people with dependence and high or repeated exposure.
The study provides useful human evidence about shared subjective pharmacology. Its cardiovascular, discrimination and performance findings nevertheless remain distinct. The absence of a significant task effect should not be converted into a declaration that every other function was unaffected.
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