Injection Drug Use

When drugs are injected, they are usually injected intravenously (1). Drugs may also be injected subcutaneously or intramuscularly, or into the vein under the tongue.

Individuals who inject drugs intravenously typically begin with peripheral veins and with habitual use move on to larger and sometimes central veins (eg, internal jugular, femoral, axillary). Eventually, injection causes sclerosis of the accessible parts of the vasculature, and then people may resort to subcutaneous or intramuscular injections.

To make an injectable form of a xenobiotic, people may take oral forms and crush them or crush tablets, dissolve them into a solution, and inject the resulting mixture. Tablets often contain filler agents such as cellulose, talc, or cornstarch, and this method introduces these agents into the bloodstream. These fillers are not safe for parenteral administration. Filler agents in the circulatory system can become trapped in the pulmonary capillary bed and result in chronic inflammation and foreign body granulomatosis. They can also damage the endothelium of heart valves, increasing the risk of endocarditis.

Xenobiotics such as heroin and cocaine are often “cut” with adulterants (eg, amphetamines, clenbuterol, dextromethorphan, fentanyl, ketamine, levamisole, lidocaine, lysergic acid diethylamide [LSD], pseudoephedrine, quinine, scopolamine, xylazine, caffeine) (2, 3). Adulterants may be added to enhance mind-altering properties or to substitute for pure drug because of expense or other factors. Adulterants increase risk of toxicity and complicate diagnosis and treatment. For example, cocaine is increasingly adulterated with fentanyl to increase its addictive qualities and reduce dysphoria and acute paranoia. This can lead to unintentional opioid overdose. However, administering naloxone to patients with cocaine toxicity is associated with an increased risk of tachydysrhythmias. Also, fentanyl is frequently adulterated with xylazine, a powerful nonopioid sedative and may lead to the clinical scenario of an "opioid overdose not responsive to naloxone" (4).

Sharing needles and nonsterile injection techniques can lead to infectious complications, including abscesses and cellulitis near the sites of injection, cellulitis, lymphangitis, lymphadenitis, and thrombophlebitis. Distal infectious complications include septic emboli, including to the lung, bacteremia, bacterial endocarditis and abscesses in organs, and osteomyelitis (particularly lumbar vertebral). Patients may develop a spinal epidural abscess (5). In addition, patients may blood-borne viral infections (eg, human immunodeficiency virus, hepatitis C, hepatitis B).

On physical examination, people who habitually inject drugs may have track marks due to repeated injections into the same veins. Track marks are a linear area of tiny, dark punctate lesions surrounded by an area of darkened or discolored skin from chronic inflammation. They are often found in accessible sites like the antecubital fossa or forearms. They may also be found in less exposed areas such as the axilla or groin.

Subcutaneous injection ("skin popping") can cause circular scars, ulcers, or abscesses. Signs of previous abscesses may be present.

• History and physical examination

• Evaluation for complications

Patients may or may not report injecting substances.

A physical examination is needed to identify areas of concern on the skin. Because of the social stigma of substance use disorders, people with physical examination findings consistent with track marks may attribute them to frequent blood donations, bug bites, or previous injury.

People who inject substances should be evaluated for infectious diseases transmitted through use of contaminated needles, including viral hepatitis, HIV, tuberculosis, syphilis, methicillin-resistant Staphylococcus aureus and other bacteria that can cause bacteremia or endocarditis, and fungal infections.

• Treatment of toxicity, dependence, and/or withdrawal

• Treatment of infectious or other complications

Patients with acute toxicity or withdrawal caused by injection drug use are treated as appropriate for the specific substance.

Treatment of infectious complications is the same as that for similar infections resulting from other conditions, including antibiotics for bacterial infections and incision and drainage of abscesses. Treatment may be complicated by difficulty obtaining venous access and by poor adherence to treatment regimens.

Wound botulism and tetanus are treated, if present.

Vaccination against hepatitis B, influenza, pneumococcal infections, and tetanus infection should be offered.

Patients should be counseled about treatment options for substance misuse and about harm reduction approaches (eg, needle exchange, access to naloxone, fentanyl testing strips) (1).

Patients should also be evaluated and offered treatment and support for other issues associated with risky behaviors, including sexually transmitted infections, intimate partner violence, food or housing insecurity, and psychiatric illness.