Although cocaine users use the drug in various forms, most can be distinguished by their preferred route of cocaine administration: inhalation (smoking crack cocaine); nasal (snorting powder cocaine); or injection (injecting a cocaine preparation) [13]. Those subgroups have been associated with specific characteristics of cocaine use: escalation of consumption; degree of abuse liability; propensity for dependence; and treatment response [14], [15]. It is argued that the reinforcing effect of smoked (crack) cocaine is greater than is that of snorted (powder) cocaine because, when the drug is smoked, the peak effect is achieved more quickly and concentrations of the drug in the central nervous system are higher for an equivalent amount of cocaine consumed [16]. Nevertheless, most cocaine-dependent patients have a preferred route of administration, despite having been exposed to both forms [13]. Therefore, the preferred route of administration can represent a distinct phenotype among cocaine users and should be taken into account when investigating individual genetic susceptibility to cocaine use and abuse.
