Analgesic effect of intraarticular morphine after arthroscopic knee surgery

Article Abstract:

Certain analgesic agents are thought to produce their effects by activating opioid receptors in the central nervous system; however, some of these opioids also directly affect opioid receptors in the body's tissues. To evaluate the magnitude of such effects, 52 patients were studied after undergoing arthroscopic knee surgery (in which the joint is directly visualized and treated using a fiberoptic device). After surgery under general anesthesia, patients received one of four sets of solutions: group 1, morphine hydrochloride in the joint (intraarticular administration) and saline intravenously; group 2, saline intraarticularly and morphine intravenously; group 3, similar to group 1, but half the dose of morphine; and group 4, morphine and naloxone (an opiate antagonist) intraarticularly and saline intravenously. Patients were asked to indicate their pain levels using a visual-analogue scale and a standard pain questionnaire at specified intervals during the first 24 hours after injection of the drugs. Results showed that the pain scores of group 1 patients (intraarticular morphine) were consistently lower than those of group 2 patients (intravenous morphine), and significantly lower three, four, and six hours after injection. Group 1 patients requested less supplemental analgesia than group 2 patients. Group 3 pain scores were higher than those of group 1, but the difference was only significant 6 and 24 hours after injection. When naloxone was combined with morphine (group 4), visual-analogue pain scores were higher than when morphine alone was given intraarticularly (group 1) at all times except 24 hours after injection of the drugs, indicating that naloxone counteracted the effects of morphine. The results indicate that intraarticular administration of morphine is more effective than systemic morphine and suggest that the drug affects opioid receptors in the joint. This route of administration is not associated with the major side effects that can accompany systemic administration of morphine. (Consumer Summary produced by Reliance Medical Information, Inc.)

Narcotics, Pain, Postoperative, Postoperative pain

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The control of pain in peripheral tissue by opioids

Article Abstract:

There is substantial evidence that peripheral nerves contain opioid receptors and that certain immune cells produce opioids following tissue injury. These naturally-occurring, endogenous opioids were thought to act only at the level of the spinal cord. But researchers have found beta-endorphin and enkephalin in immune cells such as T lymphocytes, B lymphocytes and macrophages. Studies have also shown that an injury causes the formation of opioid receptors in nerve cells that accumulate on the outside of the nerve. Opioid binding to the receptor inhibits the nerve and suppresses the release of inflammatory chemicals. Pain relief from injections of morphine during knee surgery indicates that joints contain opioid receptors. This could lead to opioid analgesics that could be injected directly into joints. This would eliminate many of the side effects of analgesics taken by mouth.

Physiological aspects, Opioids, Inflammation, Afferent pathways, Nerves, Peripheral, Peripheral nerves

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Morphine, gabapentin, or their combination for neuropathic pain

Article Abstract:

A study was conducted to compare the efficacy of a combination of gabapentin and morphine with that of each as single agent patients with painful diabetic neuropathy or postherpetic neuralgia. Gabapentin and morphine combined achieved better analgesia at lower doses of each drug either as a single agent, with constipation, sedation, and dry mouth as the most frequent adverse effects.

United Kingdom, Science & research, Pharmaceutical Preparation Manufacturing, Pharmaceutical preparations, Morphine (Unit Dose), Care and treatment, Research, Drug therapy, Combination, Combination drug therapy, Neuralgia, Gabapentin

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