Acute physiological and behavioral effects of intranasal methamphetamine in humans

Abstract

Intranasal methamphetamine abuse has increased dramatically in the past decade, yet only one published study has investigated its acute effects under controlled laboratory conditions. Thus, the current study examined the effects of single-dose intranasal methamphetamine administration on a broad range of behavioral and physiological measures. Eleven nontreatment-seeking methamphetamine abusers (two females, nine males) completed this four-session, in-patient, within-participant, double-blind study. During each session, one of four intranasal methamphetamine doses (0, 12, 25, and 50 mg/70 kg) was administered and methamphetamine plasma concentrations, cardiovascular, subjective, and psychomotor/cognitive performance effects were assessed before drug administration and repeatedly thereafter. Following drug administration, methamphetamine plasma concentrations systematically increased for 4 h postdrug administration then declined. Methamphetamine dose dependently increased cardiovascular measures and 'positive' subjective effects, with peaks occurring approximately 5-15 min after drug administration, when plasma levels were still ascending. In addition, cognitive performance on less complicated tasks was improved by all active methamphetamine doses, whereas performance on more complicated tasks was improved only by the intermediate doses (12 and 25 mg). These results show that intranasal methamphetamine produced predictable effects on multiple behavioral and physiological measures before peak plasma levels were observed. Of interest is the dissociation between methamphetamine plasma concentrations with cardiovascular measures and positive subjective effects, which might have important implications for potential toxicity after repeated doses.

Figure 1

Upper panel (left): methamphetamine plasma levels as a function of methamphetamine dose and time. Upper panel (right): heart rate as a function of methamphetamine dose and time. Lower panels: systolic and diastolic pressure as a function of methamphetamine dose and time. Error bars represent one SEM. Overlapping error bars were omitted for clarity.

Figure 2

Selected subjective-effect ratings as a function of methamphetamine dose and time. Error bars represent one SEM. Overlapping error bars were omitted for clarity. An arrow indicates the time that participants ate lunch.

Figure 3

Selected subjective-effect ratings as a function of methamphetamine dose and time. Error bars represent one SEM. Overlapping error bars were omitted for clarity. An * indicates significantly different from placebo (P < 0.05). An ^§ indicates significantly different from 12 mg/70 kg (P < 0.05). An ^† indicates significantly different from 25 mg/70 kg (P < 0.05).

Figure 4

Selected performance effects as a function of methamphetamine dose and time. Error bars represent one SEM. Overlapping error bars were omitted for clarity.