Codeine: Composition, Therapeutic use, Treatment. Codeine effects. Reactions with other drugs.

Last modified: Thursday, 25. December 2008 - 10:16 am

Official names: Codeine, codeine phosphate, codeine sulfate, methylmorphine

Street names: T-threes, schoolboy, coties, dors and fours, cough syrup, barr (codeine cough syrup), down (codeine cough syrup), karo (codeine cough syrup), lean (codeine cough syrup), nods (codeine cough syrup)

Drug classifications: Schedule II, III, or V, narcotic

  

Key terms

ANALGESIC: A type of drug that alleviates pain without loss of consciousness.

ENDOGENOUS OPIOIDS: Naturally occurring opioids in the body; includes three classes of neurotransmit-ters — the endorphins, enkephalins, and dynorphins.

OPIATE: Drug derived directly from opium and used in its natural state, without chemical modification. Opiates include morphine, codeine, thebaine, noscapine, and papaverine.

OPIOID: A drug, hormone, or other chemical substance having sedative or narcotic effects similar to those containing opium or its derivatives; a natural brain opiate.

OPIOID RECEPTORS: Aclass of proteins on the surface of cells that bind with opioids, either endogenous or drugs. An opioid either activates (agonist) or prevents activation by another opioid (antagonist).

  

Overview

Codeine is classified as an opiate analgesic. Analgesics are substances that, when ingested or injected, diminish or relieve pain; opiates are drugs that can be derived from opium. Opiates, along with opioids, the broader group to which opiates belong, are the most effective of all analgesics. All opioids are analgesics, but most analgesics are not opioids.

Many different drugs act as analgesics. One method of classifying these drugs is to separate them into two groups — those that require a doctor’s prescription and those that do not. Medications that do not require a doctor’s prescription are called over-the-counter (OTC) drugs. OTC analgesics include acetaminophen (Tylenol), aspirin, and ibuprofen. Codeine, a prescription analgesic, is one of the most frequently prescribed medications used worldwide to treat pain.

Pain is universal; everyone experiences different kinds of acute (short-term) pain during their life. However, too much pain for too long, (moderate to severe chronic pain), can be harmful, both physically and psychologically. Approximately one-third of all people in the United States experience moderate to severe chronic pain during their life. Half of all individuals who seek medical attention report pain as their primary complaint.

Codeine and other opioid medications are used medically because of their ability to relieve physical pain — in fact, it is the only reason for their medical use as a group. A broader view of opioids reveals that they also can have profound effects on emotional pain — which is perhaps a frequent, if unconscious, reason for their non-medical use/abuse. Physical and emotional pain often have an inseparable connection between them. Even something as simple as stubbing a toe usually elicits a short, but dramatic, emotional response. However, the primary medical use for codeine is only in the treatment of physical pain.

In considering the analgesic effects of opioids such as codeine, it is important to know that the body has two connected systems, one that signals pain and another that responds to it. Both systems have interacting physical and chemical components. The physical portion includes neurons of the central (brain and spinal cord) and peripheral nervous systems. The chemical portion includes substances that aid in the transmission of signals between nerve cells (neurotransmitters), along with chemicals and proteins that have specific roles in normal nerve cell function. The most important group of neurochemicals in the pain killing system is the endogenous opioids. An “endogenous” substance is something that is naturally produced by the body. Endogenous opioids function as the body’s own analgesics.

The body’s natural painkilling system, then, involves the interaction of endogenous opioids with neurons that transmit and process pain signals. Opioid medications such as codeine mimic the effects of certain endogenous opioids. However, ingested/injected opioids tend to produce much stronger effects than those of the endogenous variety.

Opioid receptors are the cell-surface proteins which all opioids interact with to produce their effects. An opioid, whether endogenous or in drug form, fits into a receptor somewhat like a key in a lock. Opioid attachment activates the receptor and initiates complex changes in the nerve cell. Activated opioid receptors produce chemical changes that reduce the ability of a nerve cell to transmit pain signals. They also decrease the “perception” of pain by neurons in the brain. In the absence of pain, those same chemical changes can produce euphoria. Loosely translated from Greek, euphoria means “good feeling.”

Codeine is extracted from opium. Opium is a chemically complex drug derived from a flowering plant, the opium poppy. The scientific name for the opium poppy is Papaver somniferum, which translated from Greek means “poppy that causes sleep.” Opium is produced by drying the thick liquid harvested from the unripe seed capsule of the flower. It contains several different medically important chemicals known as “alkaloids” (non-acidic chemicals), the most important being morphine and codeine.

Societies have used the medicinal properties of opium for several thousand years. Even up to the early part of the twentieth century, opium was used as a medicine to treat a large variety of conditions. For some of those conditions, particularly those involving pain and/or diarrhea, it was a highly effective treatment. However, by modern standards, most of opium’s historical uses for illness would be considered medically useless or unsound because of the dangers of opium use.

Two of the most important effects of opium are its abilities to relieve pain and produce euphoria. Euphoria is best described as an exaggerated sense of well-being, possibly with mild elation or a sense of calmness. Opium’s ability to produce euphoria may be what prompted its use by so many throughout history as a cure-all. After all, while it may not have had the curative effect on a person’s illness that was suspected or promised, it usually made them feel better.

Achieving consistent results with opium has always been difficult. Different methods of production and naturally varying concentrations of morphine and codeine produce widely varying results from one batch to the next. Once the chemical methods became available, scientists were eager to isolate the active ingredient(s), hoping to produce a “pure” analgesic.

Morphine was isolated from opium in 1806, which was a significant step in scientific pharmacology. For the first time, a powerful, pain-relieving medicine was available whose effects were predictable. However, it eventually became clear that the addictive potential of morphine is equal to that of opium, with many of the same side effects. Undaunted, scientists began the quest, which is ongoing, for the “perfect” opioid — a drug with the analgesic power of morphine, but with much milder side effects and little or no addictive potential.

Codeine was extracted from opium in 1832, and was the first partial success in the attempt to discover a safer and less addictive drug. However, with fewer side effects came a less potent analgesic. About 100 mg of codeine are needed to produce the same effect as 10 mg of morphine. It was believed at the time (and it is still debated) that codeine’s milder effects on a per weight basis actually result in fewer side effects when equally effective dosages are given (i.e., 100 mg of codeine produces fewer side effects than 10 mg of morphine). For the most part, standard medical practice has been to prescribe codeine for moderate pain, and reserve morphine for more severe pain.

Semi-synthetic and synthetic opioids (meperidine, hydrocodone, fentanyl, etc.) are the result of many attempts to produce effective yet safer analgesics. The fact that both morphine and codeine are still widely used indicates that the newer opioids have been only moderately successful. However, current knowledge of the opioid system makes the goal of producing the perfect (or near-perfect) opioid analgesic a more realistic possibility in the future.

Since the middle of the nineteenth century, most social attention to opium has focused on its use as an illicit drug. In fact, in many ways it has come to symbolize the worst aspects of illegal drugs. This negative social stigma has carried over to the derivatives of opium — the opioid drugs. While there is some basis for this perception, it has unfortunately generated undue fear, even within the medical professions, that anyone using an opioid drug, even someone in pain, is at great risk of becoming addicted.

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