Injection Drug Use

Updated: Aug 19, 2021
  • Author: Gloria J Baciewicz, MD; Chief Editor: Glen L Xiong, MD  more...
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Overview

Background

Most individuals who use injection drugs inject their drugs intravenously, but subcutaneous injection (ie, "skin-popping") is also common, and intramuscular injection may occur intentionally or when the individual misses the vein or the subcutaneous space. Injecting drug use is associated with many local and systemic complications for the individual and is also associated with the transmission of infectious diseases via needle sharing and sexual activity. The most commonly injected drug is heroin, but amphetamines, buprenorphine, benzodiazepines, barbiturates, cocaine, and methamphetamine also are injected. Any water-soluble drug may be injected. Treatment of individuals who use injection drugs may be complicated by social and political barriers to treatment and by a lack of resources for public health approaches to treatment.

Both illegal drug production and injecting drug use have been globalized in recent years. Injecting drug use has diffused to countries that formerly had little problem with it. Both injecting drug use and HIV infection can spread rapidly within a community. Introduction of and rapid increase in injecting drug use is believed to be responsible for dramatic increases in HIV infection in some areas. In China, in Central Asia, and in several countries of Eastern Europe, injecting drug use is the primary risk factor for HIV infection.

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Pathophysiology

When injecting a drug intravenously, the individual introduces a bolus of the drug into the vein, producing a rapid and powerful drug high. The onset of drug effects is about 15–30 seconds for the intravenous route and 3-5 minutes for the intramuscular or subcutaneous route. Drug effects from inhaling (ie, smoking) a drug begin in 7–10 seconds, and drug effects from intranasal use (ie, transmucosal absorption) begin in 3–5 minutes.

Injecting drug use causes medical problems by introducing pathogens and other contaminants into the body via shared needles and a lack of sterile preparation and injection techniques. Medical problems also arise from damage caused by the drugs themselves (eg, morbidity and mortality associated with drug overdose). The injected drugs also may not be pure; they may be cut with irritants, such as talc, lactate, or quinine.

Death from the direct toxic effects of a heroin overdose itself is usually associated with respiratory depression, coma, and pulmonary edema. Death from the direct effects of cocaine is often associated with cardiac dysrhythmias and conduction disturbances, leading to myocardial infarction and stroke.

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Epidemiology

Frequency

According to the 2021 World Drug Report of the United Nations Office on Drugs and Crime (UNODC), 269 million people used an illicit drug in 2018. This number is expected to increase 11%, to 299 million people by 2030. [1]

The joint UNODC/WHO/UNAIDS/World Bank estimate for the number of people who injected drugs (PWID) worldwide in 2019 is 11.2 million (range: 8.9 million to 14.2 million), corresponding to 0.22% (range: 0.18 to 0.28%) of the population aged 15–64. Injecting drug use remains highly prevalent in Eastern Europe, Central Asia and Transcaucasia and North America, with rates that are 5.7, 2.8, and 2.5 times the global average, respectively. In terms of the number of PWID worldwide, most of them reside in East and South-East Asia (27%), North America (16%), and Eastern Europe (15%). [1]

Among people aged 12 or older in 2019, 57.2 million people used illicit drugs in the past year, according to the National Survey on Drug Use and Health (NSDUH). Among people aged 12 or older, the percentage who used illicit drugs in the past year increased from 17.8% (or 47.7 million people) in 2015 to 20.8% (or 57.2 million people) in 2019. [2]

Mortality/Morbidity

Morbidity and mortality may result from infection secondary to injecting drug use, sequelae of injection with adulterants added to the drug mixture, sequelae of the drug use itself, drug overdose, or violence associated with drug use.

  • According to the CDC, about 1 in 10 new HIV diagnoses in the United States are attributed to injection drug use or male-to-male sexual contact and injection drug use. Adult and adolescent PWID accounted for 10% (3,864) of the 37,968 new HIV diagnoses in the United States  and dependent areas in 2018 (2,492 cases were attributed to injection drug use and 1,372 to male-to-male sexual contactd and injection drug use). [3]  Of the 3,864 PWID newly diagnosed with HIV, most were men.

  • Another significant source of HIV infection for women is sex with partners who use injection drugs. An estimated 61% of AIDS cases in women can be attributed to injecting drug use or to sex with partners who use injection drugs. Females may use more shared injecting drug use equipment than males. [4]

  • Besides direct transmission of HIV, injecting drug use also contributes to the spread of HIV infection by perinatal transmission and by sexual contact with individuals who do not inject drugs. [5] Injecting drug use is also associated with increased levels of high-risk sexual behavior.

  • Worldwide, 40–60% of individuals who use injection drugs are estimated to be positive for hepatitis B, and 60–70% are positive for hepatitis C virus (HCV). HCV rates are high even in countries with low HIV seroprevalence. Injecting drug use is responsible for approximately 60% of HCV infections in the United States. New HCV infections in the United States have declined since 1989, [6]  but the incidence and prevalence of HCV remains high. The spread of HCV is rapid among those who are new to injecting drugs; in the United States, following initiation of injecting drug use, 50–80% become infected with HCV within 6–12 months. Reductions in risky injection-related practices among young users may improve both the burden of chronic HCV infection-related liver disease and elevated viral load-related poor treatment response. [7] Another option for reducing HCV transmission is encouraging users to use intranasal drugs as analternative to injection drugs. [8] For related information, see Medscape's Hepatitis B and Hepatitis C Resource Centers.

  • The mortality from all causes in individuals who use injection drugs is estimated to be 3–4% per year.

Demographics

Worldwide, 70–90% of those who use injection drugs are believed to be male.

The purity of heroin has been increasing, and its cost has been decreasing. Because of these factors and because of their initial desire to avoid injecting drug use, many adolescents and young adults in the United States and Europe using heroin for the first time try snorting, sniffing, or smoking heroin. New noninjecting heroin users risk making a transition to injecting drug use when their need for heroin use intensifies.

Among adolescents who inject drugs, early school truancy and expulsion may be a predictor of injecting drug use. A younger age of initiation into injecting drug use is associated with more frequent reports of risky drug use and sexual practices, as well as higher rates of HIV infection. [9]

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Patient Education

Chemical dependency treatment provides education and skills training regarding abstinence from drug use. For those individuals who are not yet able to abstain from injecting drug use, harm reduction approaches are used to educate about methods of safer injection, including the use of clean needles, sterile injection techniques, and safe disposal of needles. [10]  Such outreach approaches are effective in promoting behavior change and slowing the spread of HIV and other infections. [11, 12]

Informal needle exchange programs in the United States began as early as the 1970s. In 1988, the New York City Health Department began the first government-sponsored needle exchange program in the United States. Usually, needle exchange programs operate by exchanging the used needles for an equal number of clean needles and syringes. Needle exchange programs may make referrals for chemical dependency treatment and medical treatment and may participate in other public health initiatives, such as distributing condoms and arranging HIV testing.

In some areas, needles and syringes are available for purchase from a pharmacy without a prescription. Those who purchase needles and syringes from pharmacies are less likely to participate in high-risk activities, such as using the services of crack houses or shooting galleries.

Several countries have developed harm reduction programs with different methods, including the introduction of syringe vending machines [13]  and safe injecting areas or rooms.

Programs that distribute injectable naloxone to individuals for use in suspected overdose situations have been implemented in many larger US cities.

To reduce risks associated with injecting drug use, clinicians and public health workers must raise awareness of the health consequences and risks of injection, make contact with the target population by improving access and outreach, provide the means to change risky behavior, and gain political and community support for the measures introduced.

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