Pain, opiates for

The difference in opiate pharmacology between people with and without pain also applies to addiction. The drug-seeking behaviour synonymous with drug addiction does not occur in patients given opiates for pain relief in childbirth, operations or heart attacks (Porter and Jick, 1980). Clearly, drug addicts are not in pain, and it has consequently been argued that medical use of opiates does not produce addicts (McQuay, 2001). 

In anesthesia drugs from several groups are used as premedication. Pre-anesthetic medication can decrease the anesthetic doses which otherwise would be required to induce anesthesia and so decrease the risk for adverse effects. Pre-anesthetic medication will increase the rate of induction of anesthesia and can reduce pre-operative pain and anxiety. Drugs include benzodiazepines for sedation and their muscle relaxant properties, opiates for pain relieve and anticholinergics or histamine Hi receptor antagonists against nausea and vomiting. Neuroleptics are also used as premedication for their antiemetic effects. 

There are many peripheral organs that possess enkephalin opiate receptors the ileum, the most distal part of the small intestine, and the vas deferens are the most significant. The receptors in the ileum are responsible for the antidiarrheal activity of opiates. This is also the explanation for the severe constipation that may occur when people use opiates for pain relief. 

Methylphenidate also has been used to treat other medical conditions. For example, it has been used as a short-term treatment for depression in the medically ill, as an adjunct to conventional antidepressants for patients with major depressive disorder, and in combination with opiates for pain control. Methylphenidate has been prescribed to reduce apathy in patients with dementia or other brain diseases (28,34,35). 

In Chapter 10 we discussed the use of opiate drugs in the treatment of pain. But the use of opiates for pain relief is usually reserved for severe cases. Many effective painkillers are available over the counter, and aspirin is the most widely known and used. Acetylsalicylic acid (aspirin) is closely related to a chemical found in the bark of the willow and other trees (salicylic acid). Willow bark was used in the treatment of painful conditions and fever by the ancient Greeks and by Native Americans. Salicylic acid was isolated and used as a pain reliever in Europe, but it causes severe stomach distress. It was not until the late 19th century that acetylsalicylic acid was synthesized and named aspirin by the. Bayer Company of Germany. Aspirin has come to be one of the most important drugs in medicine. It is marketed under the brand names Anacin, Bufferin, and Excedrin to name just a few, and more than 10,000 tons of aspirin are consumed in the United States every year (Julien, 2005). 

Medicine seems never to allow for complacency. As illustrated in Figure 6, we have been trapped in the Charybodian vortex through failure to recognize that the unusually safe rates of parenteral fluid administration may become quite inappropriate for the surgical patient as a result of operation itself, anesthesia, and the use of opiates for pain. 

Opiates and other narcotics and analgesic drugs may unpre-dicatably elevate the serum amylase. The elevation may last up to 24 hours. Therefore it is important that blood for amylase determination be drawn before giving the patient analgesic drugs for pain. Elevation of the enzyme in peritoneal fluid is strong... 

A clue to possible treatments for pain was discovered in the 1970s when scientists found specialized receptor cells in neurons called opiate receptors. These receptors appeared to he well suited for accepting natural painkillers that occur in the body, such as the enkephalins and endorphins. Enkephalins and endorphins are naturally occurring painkillers similar in their action to opium, morphine, and codeine. 

Ritalin and related generic methylphenidate drugs are available by prescription for individuals six years and older. Ritalin is distributed in 5, 10, and 20 mg tablets. In addition to ADHD, methylphenidate is used for several other medical conditions. It continues to be used for narcolepsy. It has also been used in treating depression, especially in elderly populations. Methylphenidate has been suggested for use in the treatment of brain injury from stroke or brain trauma it has also been suggested to improve appetite and the mood of cancer and HIV patients. Another use is for pain control and/or sedation for patients using opiates. 

Propoxyphene (Schedule II) is another opiate prescribed for pain which is much weaker than those mentioned above. Notice the structural similarities to methadone. Its effects last longer than many other drugs in this class which means it can be taken less frequently and the potential of abuse will be lessened. It can also be formulated with aspirin or acetaminophen in order to have a summation effect. 

PHYSICAL DEPENDENCE A condition that may occur after prolonged use of an opiate, but differing from addiction because the user is dependent on the drug for pain relief, rather than emotional or psychological relief. 

Methadone and opiates were first used for pain relief, and are still chiefly used in that area of medicine. It is important to remember that methadone and other opiates do not exert their pain control by altering a person s sensitivity to pain. Rather, methadone and other opiates interfere with the transmission of pain impulses from the nervous system to the brain. They accomplish this by a variety of methods. First, they decrease the transmission of nerve signals that conduct pain messages from various parts of the body to the spine. Secondly, they prevent production of neurochemicals that transfer this pain information to the spine. Finally, they mimic the actions of endorphins, which are the body s own pain-controlling chemicals. While methadone and other opiates work quite well to control pain, they do not affect touch, vision, or hearing. 

Alanex Astra AB (12/94) Novo Nordisk (10/95) Roche Bioscience (6/96) Opiate receptor target for pain Diabetes target)s) Pain target(s)... 

Doctors are most likely to prescribe morphine or other opiates when pain is severe and expected to be short-lasting (a few days to a week), such as after injury or major surgery. This is because short-term use of opiates is less likely to lead to tolerance (loss of potency with repeated use of the drug) and dependence (addiction). However, the problem becomes more complex when the severity of the pain requires the use of pain-relieving medication for more than a few weeks, because this is when tolerance and addiction to opiates tend to develop (see the section on Opiate Addiction on page 48). 

Q4 Constipation can be a troublesome side effect of opiates used for pain relief, for example morphine and codeine. It is also a side effect of some calcium channel blocking agents, antacids containing aluminium compounds and iron salts used in the treatment of anaemia. 

Brownridge P. Epidural and intrathecal opiates for postoperative pain rehef. Anaesthesia 1983 38(l) 74-6. 

Clonidine is used in the management of hypertension, attention-deficit hyperactivity disorder, opiate or nicotine withdrawal, vascular headache prophylaxis, and as an aid in the diagnosis of pheochromocytoma. It is also used as an epidural infusion for pain management. 

Various groups have weighed in on the pros and cons of prescribing opiates for chronic pain and the debate at times is emotional. Various position statements and points of view have been expressed, but the limited space here precludes an exhaustive review of the issues. An excellent review of the appropriate use of opioid therapy for chronic pain has recently been published, and the interested reader is directed there for more information. ... 

The discovery of a naturally occurring peptide called endorphin in the brain led to a search for pain-killing drugs that would be less addictive than morphine or other opiates used to relieve pain. The new drugs would be as natural as endorphin, and they could provide new insight into the molecular processes of addiction. 

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