Injection drug use is a serious public health concern that results in high rates of illness and death. People who inject drugs are at a greater risk of severe health complications, including infections such as HIV and hepatitis C, as well as infective endocarditis, skin infections, and fatal overdoses. These health risks not only affect individuals but also place a significant burden on healthcare systems and society as a whole.

In recent years, the number of people engaging in injection drug use has increased in several regions. In Canada, the number of individuals who inject drugs rose from 130,000 in 2011 to 171,900 in 2016. In the United States, approximately one million people reported injection drug use in the past year. This increase indicates an urgent need for more effective prevention programs, harm reduction measures, and healthcare policies to address the growing issue.

Link Between Opioid Use and Injection Drug Use

Opioid use plays a crucial role in the development of injection drug use patterns. In North America, opioids are frequently prescribed for pain relief, but they are no longer recommended as the primary treatment for chronic non-cancer pain due to their potential risks and limited effectiveness over long periods.

Since the late 1990s, an increase in opioid prescriptions has been observed, largely driven by aggressive pharmaceutical marketing and a heightened importance on pain management. As a result, there has been a significant rise in opioid-related overdose deaths. Studies have found that between 21% and 29% of individuals prescribed opioids misuse them, while 8% to 12% develop an opioid use disorder. Research also shows that individuals who are prescribed opioids may have an elevated risk of transitioning to illicit opioid use and injection drug use. People with chronic pain, low socioeconomic status, mental health conditions, and a history of substance use disorders are particularly vulnerable to this transition.

Pathways to Injection Drug Use

Many individuals who use prescription opioids eventually transition to heroin and injection drug use. This progression can be attributed to several key factors. One major factor is the development of tolerance, where the body becomes accustomed to the drug, requiring larger doses to achieve the same effect. This often leads individuals to seek out stronger alternatives, such as heroin, which is cheaper and more accessible.

Another critical factor is the use of opioids to relieve withdrawal symptoms. When prescription opioids are discontinued or become difficult to obtain, individuals may turn to illicit drugs to manage their withdrawal symptoms. Additionally, some individuals begin injecting drugs because they are looking for a more intense and immediate effect than oral consumption can provide.

Restricted access to prescription opioids due to tighter regulations or involuntary tapering can also contribute to the transition to illicit drug use. Research have shown that people who are forced to discontinue opioid therapy may seek out heroin or other illicit opioids to avoid withdrawal and continue managing their pain. Longitudinal research suggests that individuals who stop opioid treatment abruptly are at a significantly increased risk of engaging in injection drug use.

Prescription Opioid Use and Injection Drug Use Initiation

A comprehensive study conducted in British Columbia investigated the relationship between chronic prescription opioid use and the initiation of injection drug use. The study analysed data from 1.7 million individuals who had undergone testing for HIV or hepatitis C, focusing on a subset of 60,000 matched individuals.

The study found that individuals with chronic prescription opioid use for non-cancer pain were between 8 to 10 times more likely to start injecting drugs compared to those who had never used opioids. Among chronic opioid users, 3% to 4% transitioned to injection drug use within five years. The risk was particularly high among younger individuals and those prescribed higher doses of opioids. Half of the 15,000 chronic opioid users in the study had been taking opioids for more than two years, indicating a prolonged period of exposure before transitioning to injection drug use.

Methodology and Limitations

The study used a population-based data source that captured all community pharmacy prescriptions. To identify individuals who began injection drug use, researchers used a validated administrative algorithm.

However, there were some limitations to the study. One limitation was the inability to establish a direct cause-and-effect relationship between opioid use and injection drug use. While the study demonstrated a strong association, it could not conclusively determine whether opioid use directly led to injection drug use initiation.

Another limitation was the potential for overestimation, as the study population included only individuals who had been tested for HIV or hepatitis C. This group may not represent the general population of opioid users. Additionally, some individuals in the study may have been using opioids for non-pain-related reasons, which could have influenced the findings. The study also faced challenges in determining the exact timing of when individuals first began injecting drugs.

Policy and Prevention Strategies

The findings from this study highlight the need for careful opioid prescribing practices to reduce the risk of transition to injection drug use. Abrupt discontinuation of opioid therapy should be avoided to prevent individuals from seeking illicit alternatives. Instead, healthcare providers should use a balanced approach to pain management, incorporating shared decision-making with patients.

Expanding access to non-opioid pain management options is a crucial part of prevention. Alternative treatments such as physical therapy, cognitive behavioural therapy, multidisciplinary rehabilitation programs, and nerve block injections should be made more widely available to patients with chronic pain. Healthcare providers should work closely with patients to develop individualised pain management plans that minimise reliance on opioids.

Prevention strategies should also focus on populations at high risk of developing opioid use disorders and transitioning to injection drug use. Young adults, men, and individuals with mental health and alcohol use disorders are particularly vulnerable. Public health initiatives should prioritise education, early intervention, and access to addiction treatment services for these high-risk groups.

Harm reduction measures play a critical role in addressing injection drug use. Providing sterile injection equipment, supervised injection sites, and opioid substitution therapies such as methadone and buprenorphine can help reduce the harms associated with injection drug use. Additionally, programs that distribute naloxone, a medication that reverses opioid overdoses, should be expanded to prevent fatal overdoses.

Comparisons to Existing Research

This study aligns with previous research that has established a link between non-medical prescription opioid use and heroin use. National surveys in the United States have found that individuals with a history of non-medical prescription opioid use are 19 times more likely to begin using heroin compared to those who have never misused prescription opioids. Among military veterans, high-dose opioid therapy has been associated with a 2.5-fold increased risk of heroin use.

Interestingly, the rates of transition from non-medical prescription opioid use to heroin (3.6% within five years) closely resemble the transition rates from prescription opioid use to injection drug use (3-4%). This similarity suggests that pain relief and withdrawal management are significant driving factors behind the progression from prescription opioids to more potent substances.

Conclusion

The study provides critical insights into the pathways leading to injection drug use among individuals prescribed opioids for chronic pain. While confounding factors may have influenced the results, the findings highlight the importance of responsible opioid prescribing, greater access to non-opioid pain management strategies, and comprehensive harm reduction approaches.

More research is needed to refine prevention efforts and explore additional factors that contribute to injection drug use initiation. Addressing this complex issue requires a multidisciplinary approach that considers both individual patient needs and broader public health concerns. By improving pain management practices, expanding harm reduction initiatives, and ensuring access to effective addiction treatment, policymakers and healthcare providers can work together to reduce the risks associated with injection drug use and improve overall public health outcomes.

Reference

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