Methamphetamine suppression and route of administration: precursor regulation impacts on snorting, smoking, swallowing and injecting.

AIMS: The route of drug administration affects risk for dependence and medical harm. This study examines whether routes used by methamphetamine treatment participants were impacted by a major drug suppression policy-federal regulation of the methamphetamine precursor chemicals ephedrine and pseudoephedrine.
DESIGN: Autoregressive-integrated moving average (ARIMA) intervention time-series analysis.
SETTING: California (1992-2004).
INTERVENTIONS: Ephedrine single-ingredient products regulation, implemented August 1995; ephedrine with other active medicinal ingredients regulation, implemented October 1996; pseudoephedrine products regulation, implemented October 1997. MEASUREMENTS: Monthly counts of non-coerced methamphetamine treatment admissions reporting snorting, smoking, swallowing or injecting. Findings After rising sharply, snorting, smoking, swallowing and injecting admissions dropped 50%, 43%, 26% and 26%, respectively, when the 1995 regulation was implemented. Snorting also dropped 38% at the time of the 1997 regulation. Snorting, swallowing and injecting remained at lower levels to the end of the study period. Smoking resurged (40%) at the time of the 1996 regulation and continued rising.
CONCLUSIONS: Precursor regulation was associated with changes in the administration of methamphetamine. Injecting, the route with the greatest health risk, entered a long-term reduction. So, too, did snorting and swallowing, two routes with lower risk for dependence. In contrast, smoking, which has a relatively high risk for dependence, dropped, then rebounded and entered a long-term rise. A possible explanation is that injecting, snorting and swallowing were largely linked with US domestic methamphetamine production, which has yet to recover from the regulations. While Mexican production, which was impacted only temporarily by the regulations and has supplanted domestic production, may have helped to diffuse smoking, a route with which it is historically correlated.