sentence: The US government regulated precursor chemicals , ephedrine and pseudoephedrine , multiple times to limit methamphetamine production/availability and thus methamphetamine problems .
paragraph: Impacts of federal precursor chemical regulations on methamphetamine arrests.  The US government regulated precursor chemicals , ephedrine and pseudoephedrine , multiple times to limit methamphetamine production/availability and thus methamphetamine problems . Research has found that the regulations reduced methamphetamine hospital admissions, but authors have argued that other problems were unaffected. This study examines whether the regulations impacted methamphetamine arrests. ### design ARIMA-intervention time-series analysis with control series. ### setting California (1982-2001). ### measurements Dependent variable series: monthly methamphetamine arrests. Control series: monthly marijuana arrests and cocaine/heroin arrests. ### interventions Bulk powder ephedrine and pseudoephedrine: regulated November 1989. Products containing ephedrine as the single active medicinal ingredient: regulated August 1995. pseudoephedrine products: regulated October 1997. Large-scale producers used ephedrine and pseudoephedrine in these forms. Ephedrine combined with other active medicinal ingredients (e.g. various cold medicines)-used mainly by small-scale producers: regulated October 1996. ### findings The regulation targeting small-scale producers (1996) had no significant impact. In contrast, methamphetamine arrests stopped rising and dropped 31% to 45% each of the three times precursor chemicals used by large-scale producers were regulated. Within 3 years of the bulk powder regulation (1989) and again within 2 years of the ephedrine single ingredient regulation (1995), arrests fully rebounded. During the 4 years following the last regulation (pseudoephedrine products, 1997) arrests only partially rebounded. These effects parallel those reported on hospital admissions. The control series were generally unaffected. ### conclusions Precursor regulations targeting large-scale producers impacted methamphetamine arrests, a criminal justice problem, much as they impacted the public health problem of methamphetamine hospital admissions. Ongoing research is needed to determine whether these problems eventually fully rebound from the last regulation.