This chapter has drawn on key major reviews of the effectiveness of pharmacological interventions for psychostimulant users (Gowing et al., 2001; Shearer & Gowing, submitted).
Despite substantial research effort directed primarily at cocaine dependence, no broadly effective pharmacological therapy has been identified for cocaine or amphetamine dependence (Gowing et al., 2001). Nonetheless, several agents have been commonly used in the USA for cocaine detoxification and relapse prevention including amantadine, bromocriptine, l-tryptophan and desipramine (Halikas et al., 1993). In the UK, dexamphetamine substitution therapy has been available for amphetamine dependence (Bradbeer, Fleming, Charlton & Crichton, 1998).
The great majority of clinical trials in this area have been conducted in the USA among cocaine users, most often crack cocaine users. Clinical studies of pharmacotherapies for amphetamines are uncommon and controlled studies even rarer. Indeed, a recent systematic review (Srisurapanont et al., 2002) identified only four randomised controlled trials of treatment for amphetamine dependence.
Cocaine and amphetamines elevate mood by binding to monoamine transporters and increasing synaptic concentrations of monoamine neurotransmitters (see Chapter 3: Pharmacology of Psychostimulants). Changes induced at dopamine transporters have been postulated as the principal reinforcement underlying both cocaine and amphetamine dependence although other transporter sites may also be involved. The sensitisation of dopamine receptors and dopamine depletion through chronic stimulation may play a role in withdrawal and cravings underpinning both cocaine and amphetamine dependence (White & Kalivas, 1998). Given the apparent similarities in neurological effects of cocaine and amphetamines, the rationales underlying pharmacotherapeutic strategies for each condition have also been similar. The rationales for pharmacological interventions have been categorised in several ways. Potential strategies have included:
- drugs aimed at alleviating the discomfort of psychostimulant withdrawal, including low mood and cravings;
- aversive drugs;
- blocking drugs;
- IV drugs that treat comorbid disorders such as depression, psychosis and attention deficit hyperactivity disorder; and
- replacement therapy.