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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Opioid substitution treatment for dependence may alter sensitivity to pain. Previous studies on pain sensitivity in methadone maintenance patients have yielded contradictory results. This study compared nociceptive responses between 16 patients on stable, once daily, doses of methadone and 16 matched control subjects. Two types of nociceptive stimuli were used: (1) electrical stimulation; and (2) a cold pressor test. Two parameters were measured: detection for onset of pain, and pain tolerance. Methadone patients were tested over an inter-dosing period: at the time of trough plasma methadone concentration (0 h), and 3 h after their daily dose. Control subjects were tested twice 3 h apart. Blood samples were collected to determine plasma methadone concentration. In methadone patients, trough to peak increases in mean R-(-)- and S-(+)-methadone concentrations (118 and 138 ng/ml to 185 and 259 ng/ml, respectively) resulted in significant increases in pain detection and tolerance values for both nociceptive stimuli. Using electrical stimulation, methadone patients' pain tolerance values were lower than controls at 0 h, but higher than controls at 3 h; no significant differences in pain detection values were found. For the cold pressor test, methadone patients detected pain significantly earlier than controls at 0 h, and were also substantially less pain tolerant than controls at both 0 and 3 h. There were no significant differences in pain detection values between the two groups at 3 h. Pain tolerance to pain detection ratios for methadone patients were significantly lower than controls for the cold pressor test at 0 and 3 h, and for electrical stimulation at 0 h only. In summary, the relative pain sensitivity of methadone maintenance patients is determined by the nature of the nociceptive stimulus (e.g. cold pressor test versus electrical stimulation), the plasma methadone concentration (trough versus peak plasma concentration), and whether thresholds are determined for detection of pain or pain tolerance. Although responding to changes in plasma methadone concentration, maintenance patients are markedly hyperalgesic to pain induced by the cold pressor test.
Pain 2001 Feb 01
PMID:Hyperalgesic responses in methadone maintenance patients. 1240 39

Methadone is a potent synthetic opioid analgesic best known in Australia as maintenance therapy for narcotic addicts. Acceptance of methadone in cancer pain management is limited by a poor understanding of its pharmacokinetics and confusion about dosage. Many opioid conversion charts underestimate the potency of methadone, resulting in the risk of toxicity. Methadone is a valuable addition to the armamentarium of clinicians treating severe cancer pain, particularly neuropathic pain, that is poorly responsive to opioids or where opioid side effects are unacceptable.
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PMID:The rediscovery of methadone for cancer pain management. 1141 89

Methadone is currently best known for its use as the maintenance drug in opioid addiction. The main concern when using methadone for the treatment of pain is its long and unpredictable half-life, which is associated with the risk of delayed toxicity. This may result in side effects such as sedation and respiratory depression if careful titration and close observation of individual patient responses are not performed. For this reason, methadone is often viewed as a second line opioid, after other opioids with a more predictable dose-response have been tried. We report six patients with long-term exposure to methadone as a treatment for heroin dependency, who were also treated with methadone for cancer pain. The first five patients were at least partially refractory to the analgesic effects of opioids other than methadone. All six patients achieved analgesia without sedation or respiratory depression from aggressive upward methadone titration. Methadone analgesia can be considered early in the course of treatment of patients with chronic exposure to methadone who develop new or worsening pain requiring opioid therapy.
J Pain Symptom Manage 2001 Feb
PMID:Methadone analgesia in cancer pain patients on chronic methadone maintenance therapy. 1122 67

Tenesmus is a painful sensation of incomplete evacuation of the bowel and is often associated with poorly localized perineal pain. We describe a 68-year-old man with locally advanced rectal carcinoma metastatic to lung and with unbearable rectal-perineal pain unresponsive to morphine and ketorolac. Treatment with oral methadone was successful and pain improved considerably. Methadone has been reported to improve pain relief in patients with morphine resistance, and it is lipophilic and exerts a lesser activity on opioid receptors in the gastrointestinal tract.
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PMID:Methadone in treatment of tenesmus not responding to morphine escalation. 1130 71

Methadone, a synthetic opioid, has unique pharmacodynamics and pharmacokinetics, which contribute to its unique ability to relieve pain unresponsive to other potent opiates and its unique dosing and drug interactions. Several guidelines of administration have been established. Physicians who are involved in pain management should have a fundamental understanding of methadone's unique properties.
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PMID:Methadone for relief of cancer pain: a review of pharmacokinetics, pharmacodynamics, drug interactions and protocols of administration. 1176 77

Methadone is recommended as being free of some of the neuropsychological side effects noticed with morphine, which are attributed to active metabolites. A patient that received methadone for cancer-associated pain developed myoclonus as a side effect. This has rarely been reported before in the literature. The pathophysiology and management of myoclonus are discussed.
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PMID:Methadone-induced myoclonus in advanced cancer. 1140 80

We have previously shown that methadone maintenance patients are hyperalgesic. Very little is known about the antinociceptive effects of additional opioids in these patients. This study (1) compared the intensity and duration of antinociceptive responses, at two pseudo-steady-state plasma morphine concentrations (C(SS1) and C(SS2)), between four patients on stable, once daily, doses of methadone and four matched control subjects; and (2) determined, in methadone patients, whether the antinociceptive effects of morphine are affected by changes in plasma R(-)-methadone concentration that occur during an inter-dosing interval. Two types of nociceptive stimuli were used: (1) a cold pressor test (CP), (2) electrical stimulation (ES). Morphine was administered intravenously to achieve the two consecutive plasma concentrations. Blood samples were collected, concurrently with nociceptive responses, to determine plasma morphine concentrations. Methadone patients achieved mean C(SS1) and C(SS2) of 16 and 55 ng/ml respectively; those of controls were 11 and 33 ng/ml. Methadone patients were hyperalgesic to pain induced by CP but not ES. Despite significantly greater plasma morphine concentrations, methadone patients experienced minimal antinociception in comparison with controls. Furthermore in methadone patients, the antinociception ceased when the infusion ended. In comparison, the duration of effect in control subjects was 3 h. The fluctuations that occurred in plasma R(-)-methadone concentration during an inter-dosing interval had little effect on patients' responses to morphine. Our findings suggest that methadone patients are cross-tolerant to the antinociceptive effects of morphine, and conventional doses of morphine are likely to be ineffective in managing episodes of acute pain amongst this patient group. Further research is needed to determine whether other drugs are more effective than morphine in managing acute pain in this patient population.
Pain 2001 Aug
PMID:Methadone maintenance patients are cross-tolerant to the antinociceptive effects of morphine. 1142 27

The 1999 Federal regulations extend the treatment options of methadone-maintained opioid-dependent patients from specialized clinics to office-based opioid therapy (OBOT). OBOT allows primary care physicians to coordinate methadone therapy in this group with ongoing medical care. This patient group tends to be poorly understood and underserved. Methadone maintenance therapy is the most widely known and well-researched treatment for opioid dependency. Goals of therapy are to prevent abstinence syndrome, reduce narcotic cravings and block the euphoric effects of illicit opioid use. In the first phase of methadone treatment, appropriately selected patients are tapered to adequate steady-state dosing. Once they are stabilized on a satisfactory dosage, it is often possible to address their other chronic medical and psychiatric conditions. The maintenance phase can be used as a long-term therapy until the patient demonstrates the qualities required for successful detoxification. Patients who abuse narcotics have an increased risk for human immunodeficiency virus infection, hepatitis, tuberculosis and other conditions contributing to increased morbidity and mortality. Short- or long-term pain management problems and surgical needs are also common concerns in opioid-dependent patients and are generally treatable in conjunction with methadone maintenance.
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PMID:Methadone therapy for opioid dependence. 1143 Apr 50

As was the case in the era before us, in the new millennium we will continue to see an abundance of patients experiencing cancer-related pain for different reasons. Although much needless pain and suffering still affects many of those with cancer, we are presented with a medical dichotomy. With the analgesic drugs available today, and the relatively simple and effective guidelines to treat cancer pain published and disseminated by the World Health Organization, why do people with cancer continue to experience pain? As we search for the answer, the horizon may hold promising new drugs, 'old drugs' with new interest and applications, and new strategies for the field of pain therapy. Possibilities include the isolation and development of analgesics or analgesic combinations that may minimise the adverse effects which are often associated with the current therapeutic class of opioid analgesics. In addition, current research points to promising results identifying the N-methyl D-aspartate non-opioid receptor as a likely component of neuropathic pain. Drugs such as gabapentin, the mechanism of action of which is not well known, have found favour within the clinical community for their analgesic properties and good tolerability. Methadone, in a phase of resurgence, has garnered the attention of the clinical community because of its unique receptor activity and pharmacoeconomic benefits. A number of clinical studies have demonstrated that methadone has a valuable role in treating cancer pain. Perhaps, an unbalanced focus on the risks of inappropriate use, rather than the benefits, should not compromise or distract from the use of methadone as an alternative to morphine. Studies are on going to assess the potential role of methadone in treating neuropathic pain. Drugs such as cannabinoids, although currently applicable for patients with anorexia, nausea and/or vomiting, may offer benefits to patients experiencing pain. Other opportunities exist with such compounds as alpha2-adrenergic agonists, nicotine, lidocaine and ketamine. New strategies such as the switching opioids and/or their route of administration may offer improved analgesia with fewer adverse effects, thus providing therapeutic alternatives for the clinical community. In addition, there is interest in the co-administration of opioids that act on different receptors. For instance, oxycodone appears to be a kappa opioid receptor agonist and may offer enhanced analgesia when combined with morphine.
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PMID:Strategies for the treatment of cancer pain in the new millennium. 1143 51

Methadone is used increasingly as a second-line opioid in the management of cancer pain refractory to conventional opioids. Recent case studies suggest that its use as an analgesic could be extended to non-cancer pain, especially neuropathic pain. The present case study reports, for the first time, the efficacy of methadone in a burn patient experiencing neuropathic pain in his healed wounds. The patient sustained extensive (55% total body surface area) chemical burns and developed chronic burning sensations, particularly in the lower limbs where skin grafting had been performed. Conventional pharmacotherapies against neuropathic pain were attempted to control pain for over 5 years. The agents used included long- and short-acting opioids, amitriptyline, clonazepam, and gabapentin, but they all failed to relieve the pain. When methadone (5 mg every 12 h) was introduced, it significantly alleviated the patient's pain within a few days of administration. The patient has now been taking methadone (15 mg every 12 h) for 10 months and reports that the opioid caused 70% pain relief and a 55% amelioration in his quality of life. Although these results are based on a case report, they suggest that a switch to methadone might be useful in some burn patients who have developed chronic neuropathic pain unrelieved by conventional pharmacotherapies. Methadone, however, needs to be titrated with vigilance and thus should be administered by a physician experienced with its use in the treatment of chronic pain.
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PMID:Successful use of methadone in the treatment of chronic neuropathic pain arising from burn injuries: a case-study. 1160 Feb 60


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