Figure 7.

Essential/precursor chemical controls and monthly median cocaine, heroin and methamphetamine purity in the conterminous US (January 1987–April 2011). Cocaine chemical regulations are listed in the cocaine graph; heroin chemical regulations are listed in the heroin graph 5; and methamphetamine controls are listed in the methamphetamine graph 38, 39, 41. Following Mexico's controls, multiple types of methamphetamines (including relatively low potency types such as l‐methamphetamine and racemic methamphetamine) became commonplace 41. This limits comparisons of the methamphetamine series prior to Mexico's controls with that post‐Mexico's controls