Description

Heroin is a semisynthetic derivative of opium. The opioid family includes the following:

• Drugs that occur naturally in opium (from the poppy plant)
• Codeine
• Morphine
• Semisynthetic derivatives (e.g., hydromorphone, oxycodone)
• Synthetic compounds (e.g., meperidine, fentanyl, methadone)

Epidemiology

• General
  • 23 years of age: mean age of 1st use (2012)
  • ~50% of those who have used an opioid pain reliever for nonmedical uses state they obtained it for free from a friend or relative.
  • Nonmedical use of opioid pain relievers can lead to eventual injection heroin use.
• Neonatal
  • Fetal exposure commonly involves polysubstance abuse.
  • 60–80% of heroin-exposed infants develop withdrawal—dependent on maternal dosing and length of use.
• Adolescents
  • Most use experimentally or intermittently; few become addicted and use daily.
  • Use of opioid analgesics has increased dramatically over the last 10 years and has become more common than heroin use.
  • Most common substances were oxycodone, hydrocodone, and methadone
• Overdose
  • Up to 1/3 of heroin users experience nonfatal overdose.
  • Most occur in the home and with other people present.
  • Risk factors include length of injecting history, concurrent use of CNS depressants, recent completion of substance abuse program, and recent release from prison.
• Deaths
  • Most heroin deaths occur when drug is administered IV.
  • Most deaths in patients in their late 20s or 30s, with significant drug dependence
  • Males are 4 times more likely to die than females from heroin-related causes.
  • Multiple drug use common in heroin-related death
  • As of 2011, opioid pain relievers are responsible for more overdose fatalities than heroin and cocaine combined.

Pathophysiology

• Well-absorbed from gastrointestinal (GI) tract, nasal mucosa, pulmonary capillaries, and SC and IM injection sites
• Oral dose less potent than parenteral because of 1st-pass hepatic metabolism
• IV heroin peaks in <1 minute; intranasal and IM heroin peak in 3–5 minutes.
• Very lipid soluble; crosses blood–brain barrier within 15–20 seconds
• Extensive distribution into skeletal muscle, kidneys, liver, intestine, lungs, spleen, brain, and placenta
• Rapidly crosses the placenta, entering fetal tissues within 1 hour
• Crosses into breast milk in quantities sufficient to cause addiction
• Excreted in urine as morphine
• Receptor types
  • Mu (or OP3)
    • Located in CNS, GI tract, and sensory nerve endings
    • Effect: analgesia, euphoria, respiratory depression, physical dependence, GI dysmotility, miosis, pruritus, bradycardia
    • Kappa (or OP2)
    • Located in CNS
    • Effect: analgesia, miosis, diuresis, dysphoria
    • Delta (or OP1)
    • Located in CNS
    • Effect: spinal analgesia, modulation of mu receptors/dopaminergic neurons