Opioids are powerful pain relievers. The use of methadone for opiate maintenance in the early 1960s was a major development in combating the use of heroin. Opium is extracted from the plant Papaver somniferum. The main active ingredient is alkaloid morphine. Opioids, meaning opiate-like, are derivatives of opium. All opioids can produce euphoria and can be used as analgesics. Opioids can be classified as the following:
- Naturally occurring opium derivatives like Morphine
- Partially synthetic derivatives of morphine – Heroin, oxycodone, oxymorphone
- Synthetic compounds – Fentanyl, alfentanil, levorphanol, meperidine, methadone, codeine, propoxyphene
The term narcotic means drugs producing narcosis or sleep. Although narcotics do produce sleep, the term does not indicate their major therapeutic use today.
Opioid receptors in the mammalian CNS include mu, kappa, sigma, delta, and epsilon subtypes. These receptors are located in the brain (mostly in the periaqueductal grey), spinal cord, peripheral nerves, adrenal medulla, ganglia, and gut. Stimulation of mu and sigma receptors produces intense feelings of well-being and euphoria. Kappa-receptor
stimulation produces dysphoria. Antagonists block euphoria produced by opioids.
The dopaminergic mesolimbic system, which originates in the ventral tegmental area (VTA) of the midbrain and projects to the nucleus accumbens, is crucial in the reward effects of intracranial self-stimulation, the natural rewards of water and food intake, and the action of drugs of abuse, including opioids. Basal activity of this system, expressed in
dopamine release in the nucleus accumbens, is under the tonic control of two opposing opioid systems, activation of mu- and sigma-receptors increases, while kappa-receptor activation decreases the basal activity of the mesolimbic system.
Experimental evidence with laboratory animals supports the idea that manipulation of these receptors with opioids and other substances of abuse (as well as electrical stimulation) affects self-administering behavior. These reward pathways are thought to have evolved for the natural rewards such as food and water intake.
A survey by the National Institutes of Health (NIH) demonstrates an upward trend in new heroin use since 1991. The prevalence of past 30-day heroin use increased from 68,000 in 1993 to 216,000 in 1996 and is now over 420,000 in 2018. The lifetime prevalence of non-medicinal use of narcotics is even higher. According to the National Comorbidity Survey performed in 1990-1992, 20-32% of people who are lifetime heroin users became dependent, while only 7.5 % of people who used analgesics became dependent. According to the national, school-base Monitoring the Future Study, the percentage of 8th, 10th, and 12th graders who have used heroin has more than doubled since the late 1990s. This increase has largely been attributed to decreased price and increased purity in the last decade. Epidemiologic data indicate that the non-medical use and abuse of prescription opioids is increasing in the United States. Results from a surveillance program called the researched Abuse, Diversion, and Addiction-Related
Surveillance (RADARS) system has determined that OxyContin, a sustained-release preparation of oxycodone hydrochloride, is the most commonly abused prescription opioid analgesic. Prevalence of abuse was rank ordered as follows:
- OxyContin, Hydrocodone, other oxycodone preparations such as Methadone, Morphine, Hydromorphone, Fentanyl and Roxycodone. The death rate of people who use opioids is disproportionately high compared with that of people who use other IV drugs such as cocaine and phencyclidine (PCP).
- Heroin overdose comprises a substantial component of opioid-related mortality. Most deaths occur among IV heroin addicts in their late 20s or early 30s who have used heroin for 5-10 years. A recent period of abstinence may reduce tolerance and increase risk of overdose, and addicts have a 7-fold risk of overdosing in the first 2 weeks after leaving a residential treatment program. Fentanyl spiking has further increased risks for heroin abusers. Additionally, spraying on marijuana is now common.
- Violence associated with buying or selling narcotics also causes mortalities. In some areas of the United States, death rates from drug-related violence are higher than death rates associated with overdose or HIV.
- Screening tests for Hepatitis A, B, and C are positive in up to 90% of IV heroin users. HIV infection is also very common in this population, with rates as high as 60% among heroin users in some areas of the United States.
- Males abuse opioids more commonly than females, with the male-to-female ratio being approximately 3:1 for heroin and 1.5:1 for prescription opioids.
- New heroin use has a negative association with age. Most people who are new users of heroin are younger than 26 years, mostly college and high school students.
- Heroin use within the last 30 days was around 0.6 % in people aged 12-17 years, and the incidence of use decreases gradually in older age groups. The lifetime prevalence of opioid use in people aged 12-17 years is around 2.3%, and it is slightly higher in people aged 35-44.
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