Meperidine: Therapeutic use, Treatment. Meperidine rehab.
Last modified: Sunday, 31. May 2009 - 5:16 pm
ANALGESIC: A type of drug that alleviates pain without loss of consciousness.
MORPHINE: The primary alkaloid chemical in opium, used as a drug to treat severe acute and chronic pain.
NEUROTRANSMITTER: A substance released by one nerve cell that activates or inhibits a neighboring nerve cell.
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.
SYNTHETIC OPIOID: An opioid drug produced from chemicals that are created in a laboratory.
Meperidine is a synthetic, opioid analgesic. An analgesic is any drug or substance that, when ingested or injected, diminishes or relieves pain. Another word for analgesic is “painkiller.” Many different drugs act as analgesics. One method of classifying analgesics is to distinguish between those that require a doctor’s prescription and those that do not. Medications obtainable without a doctor’s prescription are known as over-the-counter (OTC) drugs. OTC analgesics are the most familiar, and include such medications as acetaminophen (Tylenol), aspirin, and ibuprofen (Advil; Midol).
The most effective and widely used prescription analgesics belong to a class of drugs known as opioids. Opioid drugs can be classified as natural, semi-synthetic, or synthetic. Natural opioids are also frequently referred to as opiates. Both terms, opiate and opioid, are derivations of opium. The drug groups were so-named because they produce effects similar to opium, which itself is a plant-based, chemically complex drug. Opium has been used throughout recorded history for both medicinal and recreational purposes.
Opium is made by drying the liquid that comes from the unripe seed capsule of the opium poppy, a flowering plant common to certain parts of the world. References to opium and its medicinal value have been found in writings dating from several thousand years ago. Up until the twentieth century, opium was prized for its ability to alleviate pain, treat diarrhea, and elevate mood. In addition to its well-established use as a treatment for pain and diarrhea, opium was touted and used as a cure for a wide range of other medical problems. In truth, however, opium had little or no real medical effects on the majority of those conditions. Instead, its ability to produce euphoria, a profound sense of well-being and calmness (elevated mood), made opium appear to be a highly effective medicine. After all, regardless of the illness or condition, a person who used opium nearly always felt better, whether or not they were truly getting better. In higher quantities, opium is also effective at inducing sleep. In fact, the scientific name for the opium poppy is Papaver somniferum, Greek for “poppy that causes sleep.” In even greater quantities, opium can induce coma and death.
Although opium has genuine medical benefits, it also poses significant risks. Perhaps most important is the inherent difficulty in predicting how weak or strong opium’s effects will be on any particular occasion. The concentrations of the primary active chemicals, morphine and codeine, can vary significantly from one batch of opium to the next. One reason a drug abuser might prefer prescription over illegal drugs is that they always know how much of a prescription drug they are taking. Someone who buys heroin, for instance, could be getting a nearly pure drug, or could be purchasing mostly corn-starch. Used as a medicine, opium was a risky proposition. Once the technologies in chemistry were developed, researchers in medicine and pharmacology were eager to purify the active chemicals in opium.
Along with knowledge of its desirable effects, people in ancient times were no doubt also aware of opium’s undesirable effects. Serious forms of psychological and physical addiction can develop after even short-term opium use. The highly addictive nature of opium, and by extension the opioids, tends to overshadow all other issues related to the drugs. Aside from developing predictable drugs, the primary reason for previous and ongoing research in this area is to develop a powerful analgesic with as few of the harmful side effects of opium and the current opioids as possible. Addictive potential is the side effect researchers would most like to eliminate.
It was not until 1806 that a German chemist was able to isolate morphine from opium. This was a major breakthrough in pharmacology; a pure, highly effective analgesic was finally available. Unlike opium, morphine’s potency is always the same, which allows for accurate scientific study of its effects. Data from studies of morphine have provided specific information about the safest and most effective dosages to use.
Morphine was the first limited success of attempts to improve on opium. The medical community was initially hopeful that, in addition to its analgesic power, morphine would be the break-through drug for treating opium addiction. In fact, morphine was successful in that regard; opium addicts that were given morphine were often cured of their addiction. However, it became painfully clear that those same patients developed an equally powerful addiction to morphine. The isolation of codeine in 1832 was also a limited success; it produces fewer side effects and is less addictive, but is much less potent than morphine.
Meperidine was first synthesized in the late 1930s, and was one of the first synthetic opioids. The fact that both morphine and codeine are still widely used, though, indicates that meperidine, along with all of the opioids produced since that time, have been only modest successes. Research continues with the hope of discovering the “perfect” opioid analgesic.
To understand the benefits and drawbacks of opioid drugs, one needs to understand their primary effects on the body; specifically, how they function as pain relievers. In the broadest sense, there are two types of pain — physical and emotional. Physical pain, while unpleasant, is necessary for survival. It serves as notification of the presence of injury or disease, which in turn prompts a person to take appropriate, possibly even life-saving action. Half of all individuals who seek medical attention report pain as their primary complaint.
Opioids produce their effects by interacting with cell-surface proteins known as opioid receptors. An opioid, whether endogenous (naturally produced by the body) or in drug form, fits into a receptor somewhat like a key in a lock. This 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. If opioids are used when one is not in pain, those same chemical changes in the brain’s nerve cells can produce feelings of euphoria.
In a basic sense, both the good (analgesia) and bad (addiction) effects of opioids are caused by the same process: the interaction of drugs with nerve cells, especially those in the brain. As a neuron transmits or processes pain signals, it is functioning in an abnormal, hyperactive state. Opioids work to reduce that activity and bring the neuron back toward a more normal state. Applying the opioid effect to a neuron that is already in a normal state, however, tends to force the response of neurons in the opposite direction of pain, toward pleasure (euphoria). If neurons remain in this artificially produced state for any length of time, they become tolerant of the effect. Once the opioid is removed, the affected neurons move back toward the pain end of the spectrum, something known as the “rebound effect.”
People that use meperidine for acute pain, such as after an injury, typically do not have long enough exposure to develop tolerance and addiction. People with chronic pain, however, may develop some tolerance and physical addiction in the sense that, if they stop the drug, their pain returns. Only rarely, though, do people using opioids long-term for legitimate medical reasons develop psychological addiction. A person who begins abusing an opioid drug to get high, and continues using the drug, will develop both physical and psychological tolerance and addiction. Eventually, they will need the drug not to get high, but to keep from having the pain of withdrawal. These scenarios also apply to endogenous opioids, although to a much lesser extent. For instance, athletes that produce high levels of endorphins — one of the endogenous opioids — after exercise often report that they feel depressed if they stop exercising.