The Clinical journal of pain
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Randomized Controlled Trial
Effect of chronic oral gabapentin on capsaicin-induced pain and hyperalgesia: a double-blind, placebo-controlled, crossover study.
There is an abundance of literature on the efficacy of gabapentin for the treatment of neuropathic pain. Two studies have demonstrated an effect of a single dose of gabapentin on experimental cutaneous hyperalgesia. This study evaluated the effect of chronic delivery of oral gabapentin on experimentally induced cutaneous hyperalgesia. ⋯ This study demonstrated a lack of effect of the chronic delivery of oral gabapentin on experimentally induced cutaneous hyperalgesia. The discrepancy of this finding with other studies using single oral doses may be the result of differences in the models used and differences in drug kinetics and plasma levels. The results of this study do not correlate with the clinical studies on gabapentin, which demonstrate efficacy at 1800 mg/d.
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Review
Predicting opioid misuse by chronic pain patients: a systematic review and literature synthesis.
Opioids can provide relief for people with chronic pain. However, a minority may develop aberrant drug behaviors. A critical issue is identifying "at-risk" patients. ⋯ Review of the published studies reveals that no one procedure or set of predictor variables is sufficient to identify CPP at-risk for opioid misuse or abuse. There is a scarcity of evidence regarding characteristics that predict aberrant behavior before beginning long-term opioids. Several predictors have been identified. Strong predictors include a personal history of illicit drug and alcohol abuse. Demographic factors have also been reported, but the results are not consistent. Prospective studies, especially ones with CPP who have not already been started on chronic opioid therapy, are needed.
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Opioid-induced hyperalgesia (OIH) is most broadly defined as a state of nociceptive sensitization caused by exposure to opioids. The state is characterized by a paradoxical response whereby a patient receiving opioids for the treatment of pain may actually become more sensitive to certain painful stimuli. The type of pain experienced may or may not be different from the original underlying painful condition. ⋯ OIH seems to be a distinct, definable, and characteristic phenomenon that may explain loss of opioid efficacy in some cases. Clinicians should suspect expression of OIH when opioid treatment effect seems to wane in the absence of disease progression, particularly if found in the context of unexplained pain reports or diffuse allodynia unassociated with the pain as previously observed. This review highlights the important mechanistic underpinnings and clinical ramifications of OIH and discusses future research directions and the latest clinical evidence for modulation of this potentially troublesome clinical phenomenon.
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Opioid therapy for chronic pain has been popularized over the past few decades, and a concern has arisen that the analgesic efficacy of opioids is not always maintained over prolonged courses of treatment despite dose escalation and stable pain. Considering the potentially serious adverse effects of opioids, the idea that pain relief could diminish over time may have a significant impact on the decision to embark on this therapy, especially in vulnerable individuals. ⋯ The theoretical basis for loss of analgesic efficacy over time is then examined. Mechanisms for loss of analgesic efficacy proposed are pharmacologic tolerance, opioid-induced hyperalgesia, subtle and intermittent withdrawal, and a number of psychologic factors including loss of the placebo component.
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Comparative Study
Comparable analgesic efficacy of transdermal buprenorphine in patients over and under 65 years of age.
To compare the efficacy and tolerability of transdermal buprenorphine in elderly patients and 2 younger populations, all requiring analgesic treatment for moderate-to-severe chronic pain. ⋯ This investigation showed that the treatment of chronic pain with transdermal buprenorphine in elderly patients above the age of 65 years is at least as effective, tolerable, and safe as in patients studied in 2 age-groups below that age.