INTRODUCTION AND EPIDEMIOLOGY
Illicit drug use is a major health issue globally. It is estimated that in 2011 between 167 and 315 million people worldwide used illicit substances.1 In 2012, an estimated 23.9 million Americans ≥12 years of age used an illicit drug within the previous month, and of these, 669,000 used heroin, nearly triple the prevalence in 2008.2 Between 2006 and 2011, heroin-related ED visits increased from 189,780 to 258,482, with the majority of visits made by men (69%) and patients age 35 to 44 years.2 More recently, ED visits due to severe overdoses have been precipitated by drug distributor substitution of the synthetic opiate fentanyl for heroin as a "super high."3
The practice of injection drug use and the lifestyle and culture of the injection drug user place the individual at risk for a wide variety of complications, including human immunodeficiency virus (HIV) infection, hepatitis, tetanus, sexually transmitted diseases, trauma, and intimate partner violence.4 The high incidence of migration, incarceration, homelessness, nutritional deficiencies, coincident smoking and alcohol use, and mental illness further compromises this population's health.5
Injection drug use is associated with immune dysregulation. Exaggerated and atypical lymphocytosis, diminished lymphocyte responsiveness to mitogenic stimulation and depressed chemotaxis, hypergammaglobulinemia, increased opsonin production, decreased T-cell and natural killer cell activity, high levels of circulating immune complexes, and reticuloendothelial abnormalities have been found in injection drug users. False-positive results on nontreponemal syphilis serologic tests, positive results on Coombs tests, low measured antibody response to vaccination, and thrombotic thrombocytopenic purpura are some described abnormalities. HIV-infected patients who inject drugs are found to be less likely to suppress HIV-1 RNA than those who do not inject drugs. Given the immune dysfunction, febrile injection drug users should be suspected of having infections, even when the fever is low grade and WBC counts and erythrocyte sedimentation rates are normal.
To adequately evaluate the histories of injection drug users, be aware of the drugs used locally and regionally, drug street names (e.g., "smack," "H," "Mexican mud," "junk," "bud light," "theraflu"), and drug adulterants. Ask about drug type(s) and amount, preparation of materials for injection (e.g., crushing capsules in the mouth, licking needles, blowing on injection sites or blowing out clots in needles, or using saliva, lemon juice, or tap or toilet water for drug reconstitution), reuse of needles, needle sharing, use of antibiotics, and coincident medical and mental illness. Consider socioeconomic issues, such as the ability to purchase medications and access to outpatient follow-up, in patient disposition.
Complications of injection drug use may be obvious, such as a painful, erythematous, fluctuant skin abscess. However, subtle constitutional symptoms such as weakness, anorexia, body pains, myalgias and arthralgias, weight loss, and fever are common and may be the only signs of serious underlying disease (Table 296-1).