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Injection Drug Use

by Patrick G. O’Connor, MD, MPH

A number of drugs of abuse are given by injection to achieve a more rapid or potent effect or both. Drugs are typically injected IV but may be injected sc, IM, or even sublingually. Users typically access peripheral veins, but when these have sclerosed due to chronic use, some learn to inject into large central veins (eg, internal jugular, femoral, axillary).


People who inject illicit drugs risk not only the adverse pharmacodynamic effects of the drugs but also complications related to contaminants, adulterants, and infectious agents that may be injected with the drug.


Some drug users crush tablets of prescription drugs, dissolve them, and inject the solution IV, thus injecting themselves with an array of filler agents commonly present in tablets, including cellulose, talc, and cornstarch. Filler agents can become trapped by the pulmonary capillary bed and result in chronic inflammation and foreign body granulomatosis. Filler agents can also damage the endothelium of heart valves, thus increasing the risk of endocarditis.

Street drugs such as heroin and cocaine are often “cut” with various adulterants (eg, amphetamines, clenbuterol, dextromethorphan, fentanyl, ketamine, lidocaine, lysergic acid diethylamide [LSD], pseudoephedrine, quinine, scopolamine, xylazine). Adulterants may be added to enhance mind-altering properties or to substitute for pure drug; their presence can make diagnostic and therapeutic decisions difficult.

Infectious agents

Needle sharing and use of nonsterile techniques can lead to many infectious complications. Injection site complications include cutaneous abscesses, cellulitis, lymphangitis, lymphadenitis, and thrombophlebitis. Distant focal infectious complications due to septic emboli and bacteremia include bacterial endocarditis and abscesses in various organs and sites. Septic lung emboli and osteomyelitis (particularly lumbar vertebral) are particularly common. Infectious spondylitis and sacroiliitis may occur.

Systemic infectious diseases are primarily hepatitis B and C and HIV infection. IV drug users are at high risk of pneumonia, resulting from aspiration or hematogenous spread of bacteria. Other infections that are not directly caused by drug injection but are common among IV drug users include TB, syphilis, and other sexually transmitted diseases. Even botulism and tetanus can result from IV drug abuse.


  • History, physical examination, or both

Some patients readily admit to injection drug use, but for others, a thorough physical examination is needed to detect evidence of injection. Chronic IV drug use can be confirmed by observing track marks due to repeated injections into subcutaneous veins. Track marks are a linear area of tiny, dark punctate lesions (needle punctures) surrounded by an area of darkened or discolored skin due to chronic inflammation. Track marks are often found in easily accessible sites (eg, antecubital fossa, forearms), but some drug users try to hide evidence of their injections by choosing less obvious sites (eg, axillae). Subcutaneous injection (skin popping) can cause characteristic circular scars or ulcers; there may be signs of previous abscesses. Addicts may deny stigmata of drug use by attributing track marks to frequent blood donations, bug bites, or previous trauma.


  • Prevention and treatment of infectious complications

Drug users, especially those with a history of injection drug use, should be thoroughly evaluated for viral hepatitis, HIV infection, and the wide range of other infectious diseases common among these patients (eg, TB, syphilis, other sexually transmitted diseases). Also, vaccination to prevent hepatitis, influenza, pneumococcal infection, and other infections should be offered to all appropriate patients.

The AIDS epidemic has triggered a harm-reduction movement, which aims to reduce the harm of drug use without necessarily requiring cessation. For example, providing clean needles and syringes for users who cannot stop injecting drugs reduces the spread of HIV and hepatitis.

Treatment of infectious complications is the same as that for similar infections resulting from other conditions; it includes use of antibiotics and incision and drainage of abscesses. Treatment may be complicated by difficulty obtaining venous access (and keeping the patient from using it to inject more drugs) and by poor adherence to treatment regimens.

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