Opioid Analgesics & Pain Management

July 16, 2014 – 01:35 am

Use of Opioid Analgesics in Pain Management: An Overview and Short History History Opioid analgesics have been used as medicinal agents, especially for the treatment of acute and chronic pain, for thousands of years. Ancient Greeks first identified and used these medicines, which were originally derived from opium — the latex of immature seed capsules of the poppy flower (Papaver somniferum).5, 6 From these simple beginnings, opioid analgesics have become a mainstay of medical therapy used by millions of patients each year.7 While numerous drugs have been developed for the treatment of different types of pain, no single class of agent has replaced or reached the same level of usefulness for the treatment of moderate to severe pain as have opioid analgesics.8

Opioid analgesics are often the first line of treatment for many painful conditions and may offer advantages over nonsteroidal anti-inflammatory drugs (NSAIDs). Opioid analgesics, for example, have no true "ceiling dose" for analgesia and do not cause direct organ damage; however, they do have several possible side effects, including constipation, nausea, vomiting, a decrease in sexual interest, drowsiness, and respiratory depression. With the exception of constipation, many patients often develop tolerance to most of the opioid analgesic-related side effects.8

While practitioners often express concern about the use of opioid analgesics for acute and chronic pain conditions, they are often the only suitable agent to control significant pain. This is especially true in the postoperative period.60 Morphine is the most commonly used opioid analgesic in the postoperative period, but some practitioners prefer other agents, such as hydromorphone.9 There is some debate as to whether hydromorphone is better tolerated than morphine in terms of side effects. Some recent studies, however, do not support this concept and adverse reactions to either drug are possible.9

Another area of debate concerning opioid analgesics is their use in the treatment of neuropathic pain. This area is still being explored and remains somewhat controversial. Most studies related to this question have been small, demonstrated equivocal results, and have failed to clearly establish the long-term risk/benefit ratio of these agents.10 A recent Cochrane Review found that the results were somewhat mixed; short-term trials had contradictory results, while intermediate trials demonstrated opioid analgesic efficacy for spontaneous neuropathic pain. Across trials, the side effects were nausea, constipation, dizziness, and drowsiness.10

Mechanism of Action of Opioid Analgesics

Opioid analgesics bind to a number of different receptors throughout the body—mu, delta, and kappa.8 The binding to these different receptors results in both the therapeutic and adverse effects of opioid analgesics. Genetic variations in the structure of these receptors can partially explain interindividual responses, including some adverse reactions to these agents.11

Source: www.prescriberesponsibly.com

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