Executive Summary

The use of cocaine has been associated with a range of physical and psychological harms. Many of the adverse effects of cocaine may be short-lived and not associated with long-term consequences for the user’s health. Some, however, particularly cardiovascular and cerebrovascular complications, may be fatal. In the US, cocaine has been implicated in a substantial proportion of fatal accidental drug overdoses.

Since the late 1990s, cocaine use has become increasingly prevalent among illicit drug users, particularly injecting drug users, in Sydney, Australia. Recent research has indicated that a substantial proportion of both injecting and non-injecting cocaine users in Sydney have reported serious physical and psychological symptoms associated with their use of cocaine. Moreover, these symptoms are consistent with the documented effects of cocaine and some are indicative of cocaine toxicity or ‘overdose’.

Non-fatal cocaine overdose and the adverse events that users attribute to cocaine overdose have not yet been examined in Australia, nor have they been widely studied elsewhere. The aim of the present study was to investigate the prevalence and nature of non-fatal cocaine overdose and, more broadly, cocaine-related adverse events, among injecting and non-injecting cocaine users in Sydney. The study also aimed to examine the circumstances surrounding overdose, responses to overdose in others, and users’ risk perceptions of cocaine overdose.

Two hundred cocaine users, including 120 injecting cocaine users (ICU) and 80 non-injecting cocaine users (NICU), were interviewed about their drug use history, cocaine use history, severity of cocaine dependence, history of cocaine-related adverse events, and cocaine overdose history.

Physical (49%) and psychological (42%) adverse events associated with the use of cocaine were prevalent among the sample, with 67% of ICU, and 51% of NICU, reporting at least one such symptom. Among both groups, palpitations, intense sweating and severe nausea/vomiting were the most commonly reported physical problems. The most common psychological symptoms among ICU and NICU were paranoia, anxiety and panic. These symptoms are consistent with the known effects of cocaine. Age, severity of cocaine dependence, and the extent of polydrug use were significantly associated with more extensive adverse effects.

Thirteen percent of the total sample had overdosed on cocaine. Those who had overdosed had done so on a median of 2 occasions. The prevalence of cocaine overdose was significantly higher among ICU (17% vs 6%) and females (20% vs 9%). Similarly, ICU (2 vs 1) and females (4.5 vs 1) had overdosed on a significantly greater number of occasions. Gender was the only significant independent predictor of cocaine overdose, with females being almost three times as likely as males to have overdosed. The most commonly reported symptoms of cocaine overdose were palpitations, intense sweating and seizures. Other reported symptoms included paranoia, severe agitation, respiratory distress, high body temperature, chest pain, and tremors. These symptoms are consistent with the documented indicators of cocaine overdose.

A substantial proportion of both ICU (13/20) and NICU (3/5) had been using another drug at the time of overdosing on cocaine, with heroin and alcohol, respectively, being the most common drugs used in combination with cocaine. This finding is consistent with the literature regarding fatal cocaine overdose which suggests that the risk of overdose may be increased by the use of heroin and alcohol with cocaine.

Having been present when someone else overdosed on cocaine was more common than having overdosed oneself, with 35% of ICU, and 8% of NICU, reporting that they had witnessed an overdose. Nevertheless, there were substantial proportions of both groups who stated that they would not recognise a cocaine overdose. ICU and NICU differed in terms of the way they responded to a cocaine overdose, with ICU being more likely to call an ambulance or take a person to hospital.

The majority of both ICU and NICU believed that the primary reason for cocaine overdose was using excessive amounts of cocaine, and that it was unlikely that they would overdose in the future. Substantial proportions of both groups thought, however, that it was likely that other cocaine users would overdose at least once in their lifetime.

Overall, the findings of the current study suggest that cocaine can induce serious symptoms in the context of various patterns of use, but particularly among older, more dependent polydrug users. They also highlight the importance of educating cocaine users about the possibility and nature of overdose and making them aware that cocaine overdose can occur irrespective of dose, frequency and method of use. Furthermore, users need to be aware of the potential danger of combining cocaine with other drugs, such as heroin and alcohol.

Citation: Kaye, S. and Darke, S. (2003) Non-fatal cocaine overdose and other adverse events among injecting and non-injecting cocaine users, Sydney: National Drug and Alcohol Research Centre.