The word "narcotic" is often used to describe opiate or opiate-derived drugs. At times, the word narcotic has been used inaccurately and interchangeably with drugs from other classes or categories. According to the 2002 textbook, "Drugs, Medicine and Modern Society," by C.F. Levinthal, opiates or opioids consist of ingredients found in the opium plant or derivatives; for example, dried nectar of the poppy seed. Opium plants or their derivatives, such as dried poppy juice, provide the chemicals that produce analgesic and euphoric effects. Opioids are typically grouped into the drug category of opiate-analgesics; the two words being used interchangeably. In clinical settings, opioids administered for medical purposes are referred to as prescription narcotics. According to a 2009 study by the National Institute of Drug Abuse, or NIDA, there are three sub-categories within the category of opiate-narcotics.
Pharmacology of Synthetic Opiates
Opium serves as the base for three other categories: morphine, codeine, and thebaine. Opiate derivatives are next in the hierarchy, with heroin, hydromorphone, and oxymorphine derived from morphine. Codeine stands alone. Thebaine derivatives include fentanyl, oxycodone and etorphine. Synthetic opiates include methadone, meperidine, propoxyphene, and LAAM. According to Levinthal, morphine, as an example, is often used both preoperatively and post-operatively in the management of severe pain, relief from acute diarrhea, and in cough suppression. Synthetic opioids act as powerful agonists for endogenous opioid receptor sites. Agonists are drugs that mimic and occupy the receptor sites for endogenous, or naturally occurring, neurotransmitters. For example, heroin molecules bind strongly to endorphin receptor sites, says J.P. Pinel in the 2009 book, "Biopsychology."
Methadone
In "Heroin," a 1998 publication by H. Fernandez, the author examines the origins and mainstream use of methadone. Methadone is a synthetic opioid first synthesized by the Germans during World War II. Methadone molecules bind to the same receptor sites as morphine, but they have a longer half-life and longer- lasting analgesic effects. Due to its high efficacy as an opiate agonist, methadone is regularly administered as a replacement narcotic for individuals undergoing heroin recovery. Methadone reduces drug cravings while exerting analgesic effects and it simultaneously blocks the effects of heroin in the event that the patient relapses. Its use in narcotic recovery programs began as early as the 1960s and has become a staple in the treatment of heroin addicts. Critics of methadone posit that it only serves as a substitute for heroin. In-patient programs, which require patient hospitalization, include programs that administer opioid antagonists such as Naltrexone, or partial agonists such as Buprenorphine; techniques enabling a more comfortable and secure withdrawal process.
Naturally Occurring Opiates
In his book, "Essential Psychopharmacology: Neuroscientific Basis and Application," S.M. Stahl reviews the biochemistry between the brain and opiates. The human brain produces its own variations and types of endogenous and opiate-like substances, sometimes referred to as the "brain's morphine." These substances, known as peptides, can induce endogenous, or natural, opiate-like action through the process of neurotransmission. In 1967, R.J. Martin published his findings in the "Journal of Neurophysiology." In his article,"Ventrolateral and dorsolateral ascending spinal cord pathways influence on thalamic nociception in the cat," Martin hypothesized, tested, and reported on findings supportive of the existance of multiple opioid receptor sites. He observed similar neuronal responses resulting from the administration of various types of opioids. Subsequently, Martin discovered that different opioids activated different receptor sites. In NIDA's 1986 monograph series, researchers N.M. Lee and H. Landhal published their work titled,"Opiate Receptor Subtypes and Brain Functions," They described endogenous opioids or naturally occurring opioid peptides, and classified them into three distinct groups:
1. β -- endorphins and related peptides
2. enkephalins and dynorphin
3. α-neo-endorphins.
Opiate Agonists
Agonists are drugs that mimic the effects of a particular drug. For example, heroin mimics the molecules that would bind to endogenous, or naturally occuring opiate receptor sites. In his 1995 article, "A Review of the Effects of Opioids on Psychomotor and Cognitive Functioning in Humans," J.P. Zacny examined drugs classified as "morphine like agonists." These drugs included "morphine, hydromorphine, heroin, meperidine, fentanyl, alfentanil, and methadone; as well as partial agonists including codeine, oxycodone, dihydrocodein, dextropropoxyphene, meptazinol, dipipanone, dezocine, papaveretum," Zacny also identified mixed agonist / antagonists including, buprenorphine, pentazocine, butorphanol, and nalbuphine.
Clinical Use of Opiates
Opiates, whether naturally occurring or synthetic and administered, are regarded as potentially addictive. Tolerance and dependence can be easily achieved, and quite rapidly. Opiate brain receptors adapt to drug molecules quickly, resulting in a need for higher dosages and increased frequency of dosing. Whether an individual is a pain patient or a recreational opioid user, due to the long half life of most opiates, the threshold between what the body can tolerate and what produces toxicity becomes blurred. A steady state of drug levels is variable for each individual. However, a person's response to a maintenance dose can vacillate with the onset and course of other health issues. Opiates have a high addiction potential and serious neurocognitive impairments have been correlated with opiate abuse. The dangers associated with opioids warrant close and weekly monitoring by a physician.
References
- Pinel, J.P. (2009). Biopsychology. (7th.ed.). Boston, MA: Allyn & Bacon.
- Lee, N.M., & Landahl, H. (1986). Opiate receptor subtypes and brain functions. NIDA Research Monograph Series: United States Department of Health Services.
- Zacny, J.P. (1995). A Review of the effects of opioids on psychomotor and cognitive functioning in humans. Experimental and Clinical Psychopharmacology,3(4), 432-466.
- Fernandez. (1998). Heroin.
- Levinthal, C.F. (2002). Drugs, Behavior, and Modern Society. (3rd.ed.). Boston, MA: Allyn & Bacon.
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