Temporal and geographic variations in the characteristics of heroin seized in Spain and their relation with the route of administration. Spanish Group for the Study of the Purity of Seized Drugs.

We studied the evolution of the purity and other characteristics of heroin seized in 17 Spanish provinces (especially seizures presumed to be street drugs) and explored their relation with the prevalence and recent changes in intravenous use. We found great variability in purity within and between provinces: in provinces with large cities the purity is similar to or greater than that detected elsewhere in Europe, in others it is less than 30 percent, and on the island of Mallorca it is over 60 percent. Purity has increased in recent years. The heroin in circulation is predominantly brown in all of Spain except on the Mediterranean coast. The principal adulterants detected are caffeine, paracetamol and piracetam; phenobarbital and procaine have disappeared. In provinces where white heroin is in circulation, most heroin users in treatment use the intravenous route; in provinces where brown heroin predominates, the proportion of chasers increases with increasing purity of heroin (correlation coefficient = 0.6). The disappearance of white heroin has paralleled the spread of the phenomenon of chasing.