Adverse Effects of Intravenous Heroin (Smack)
Intravenous heroin causes life-threatening respiratory depression, overdose death, and serious infectious complications including endocarditis, abscesses, and hepatitis C infection, with mortality rates of 1-3% among users.
Immediate Life-Threatening Effects
The most critical adverse effect is marked respiratory depression progressing to Cheyne-Stokes breathing pattern, with arterial oxygen saturation dropping as low as 52-90% (mean 78.9%) immediately following injection 1. This respiratory depression is the primary mechanism of overdose death, which more than doubled between 2000 and 2013 2.
Cardiovascular Complications
- Severe intermittent bradycardia occurs during hypoxic episodes in approximately 44% of users (7 of 16 subjects studied) 1
- Venous thrombosis and phlebitis extending from injection sites 3
- Risk is particularly elevated after periods of abstinence due to loss of tolerance 4
Neurological Effects
- Paroxysmal EEG activity observed in 31% of subjects (5 of 16) during injection 1
- Acute myelopathy and paraplegia from spinal cord infarction due to systemic hypoxemia and hypotension 5
- Seizures (uncommon but serious) 6
Infectious and Local Complications
Serious adverse health outcomes from intravenous drug use include 2:
- Endocarditis (bacterial infection of heart valves)
- Soft tissue abscesses
- Tissue necrosis at injection sites 3
- Hepatitis C infection (extremely common among IV users)
Musculoskeletal Complications
Atraumatic rhabdomyolysis can occur from:
- Direct toxic effects of heroin on skeletal muscle
- Coma-induced pressure on gravity-dependent body parts
- Presents with severe limb pain, swelling, and markedly elevated creatine kinase (>155,000 IU/L documented) 7
- May require urgent fasciotomy if compartment syndrome develops
Common Side Effects
Beyond life-threatening complications, heroin produces 8:
- Severe itching and urticaria (histamine reactions)
- Flushing
- Pain and nausea
- Local tenderness and febrile responses 3
Critical Clinical Pitfall
The most dangerous scenario is heroin use after a period of abstinence (voluntary or incarceration-related), as tolerance is lost but users may inject their previous dose, leading to fatal overdose 4. This accounts for a significant proportion of heroin-related deaths and requires specific counseling for patients leaving controlled environments.
Chronic Use Consequences
While addiction occurs in less than 25% of those who try heroin, for those who develop severe opioid use disorder, it becomes a chronic relapsing condition with neurologic changes in brain reward centers 2. The mortality rate among chronic heroin users ranges from 1-3% annually 4, making it one of the drugs with the most negative effects on users.