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History, Pharmacology, and Prevalence
Heroin Overview: Pharmacology

Neurobiology

The blood brain permeability of heroin is about 10 times that of morphine.[1,2]  Once heroin crosses the blood brain barrier, it is hydrolyzed into 6-acetyl morphine and morphine, which then quickly bind to opioid receptors.[2,3]  The “rush” felt by heroin users is the sensation caused by the rapid entry of heroin into the brain and the attachment of 6-acetyl morphine and morphine to opioid receptors.  Opioids in general can change the neurochemical activity in the brain stem causing a depression in breathing.  In the limbic system opioids cause an increase in feelings of pleasure, and have the ability to block pain signals sent through the spinal cord.[3]
Click here to see an animation on how heroin works in the brain.

When heroin is injected or smoked, users typically feel two types of euphoric effects–a “rush” and a “high.”  The rush usually lasts one to two minutes and occurs right after the drug is administered.  It is described as an intense orgasmic feeling that is felt throughout the body, especially in the abdomen.  Following the rush is a high that can last four to six hours.  The feeling is described as warm and pleasant, with indifference to internal and external stimuli.  The following characterizations may occur during a high[4]:

  • “Go on the nod” – sitting in a chair or lying in bed, gazing at a newspaper or the television while dozing and rousing alternatively
  • “Drive” – talking constantly, boasting, and busying oneself with chores
  • Alternately nod and drive
  • Function normally – this may lead to an observer not detecting heroin use. 

Timing of Effects

Injecting heroin intravenously can produce a feeling of euphoria in seven to eight seconds.  The peak effects of smoking heroin are similar to those obtained from intravenous injection.[5]  In contrast, injecting intramuscularly, also known as skin popping, leads to a slower onset of euphoria, taking five to eight minutes.[3]  The peak effects of snorting heroin occur in 10 to 15 minutes.[3]  Oral administration of heroin has little effect. 

 

References

  • (1) Washington N, Washington C, Wilson C. Physiological Pharmaceutics: Barriers to Drug Absorption. 2 ed. CRC Press; 2001.
  • (2) Bao G, Kang L, Li H, Li Y, Pu L, Xia P, et al. Morphine and Heroin Differentially Modulate in vivo Hippocampal LTP in Opiate-Dependent Rat. Neuropsychopharmacology 2006 Oct 24;32(8):1738-49.
  • (3) NIDA. Heroin: Abuse and Addiction. Rockville, MD: NIH; 2005 May.
  • (4) Stimmel B. The facts about drug use: Coping with drugs and alcohol in your family, at work, in your community. The Hawthorne Medical Press; 1992.
  • (5) Cone EJ. Recent discoveries in pharmacokinetics of drugs of abuse. Toxicology Letters 1998 Dec 28;102:97-101.

IllustrationsIllustrations

  • ="Brain
    Brain on Heroin