Opioid Use And Risks In Treatment Of Pain

"Some opioids used for analgesia have both agonist and antagonist actions. Potential for abuse among those with a known history of abuse or addiction may be lower with agonist-antagonists than with pure agonists, but agonist-antagonist drugs have a ceiling effect for analgesia and induce a withdrawal syndrome in patients already physically dependent on opioids.
"In general, acute pain is best treated with short-acting pure agonist drugs, and chronic pain, when treated with opioids, should be treated with long-acting opioids (see Table 2: Opioid Analgesics Tables and Table 3: Equianalgesic Doses of Opioid Analgesics). Because of the higher doses in many long-acting formulations, these drugs have a higher risk of serious adverse effects (eg, death due to respiratory depression) in opioid-naive patients.
"Opioid analgesics are useful in managing acute and chronic pain. They are sometimes underused in patients with severe acute pain or with pain and a terminal disorder such as cancer, resulting in needless pain and suffering. Reasons for undertreatment include
"• Underestimation of the effective dose
"• Overestimation of the risk of adverse effects
"Generally, opioids should not be withheld when treating acute, severe pain; however, simultaneous treatment of the condition causing the pain usually limits the duration of severe pain and the need for opioids to a few days or less. Also, opioids should generally not be withheld when treating cancer pain; in such cases, adverse effects can be prevented or managed, and addiction is less of a concern.
"In patients with chronic noncancer pain, nonopioid therapy should be tried first (see Treatment). Opioids should be used when the benefit of pain reduction outweighs the risk of adverse effects and of drug misuse. If nonopioid therapy has been unsuccessful, opioid therapy should be considered. In such cases, obtaining informed consent may help clarify the goals, expectations, and risks of treatment and facilitate education and counseling about misuse. Patients receiving chronic (> 3 mo) opioid therapy should be regularly assessed for pain control, adverse effects, and signs of misuse. If patients have persistent severe pain despite increasing opioid doses, do not adhere to the terms of treatment, or have deteriorating physical or mental function, opioid therapy should be tapered and stopped.
"Physical dependence (development of withdrawal symptoms when a drug is stopped) should be assumed to exist in all patients treated with opioids for more than a few days. Thus, opioids should be used as briefly as possible, and in dependent patients, the dose should be tapered to control withdrawal symptoms when opioids are no longer necessary. Patients with pain due to an acute, transient disorder (eg, fracture, burn, surgical procedure) should be switched to a nonopioid drug as soon as possible. Dependence is distinct from addiction, which, although it does not have a universally accepted definition, typically involves compulsive use and overwhelming involvement with the drug including craving, loss of control over use, and use despite harm."

Source: 

"Treatment of Pain." The Merck Manual for Health Professionals. Merck & Co. Inc. Last accessed September 24, 2014.
http://www.merckmanuals.com/pr...

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