Analgesic Consolidation
46. W.C. relates that he has been taking up to 18 tablets of various opioid analgesics daily. How should his pain be managed?
Chronic opiate use can lead to dependence as well as tolerance. The immediate need is to stabilize W.C.'s pain, but a longer-term goal should include analgesic tapering if tolerated. Evidence from pain studies in animal models, and in longitudinal studies of humans, indicate that chronic opioid use can lead to changes in the CNS that result in hyperalgesia. It is not known if this effect is drug- and time-dependent.156,157
Tapering is not likely to be achieved quickly, however. W.C. should be started on an opiate tapering regimen after his pain is stabilized, and this process should occur within 24 hours after the analgesic dose has stabilized. The first step in opiate analgesic tapering is opiate consolidation. As in this case, the patient often is receiving several analgesics unnecessarily. A longer-acting opioid analgesic should be used for W.C. to minimize the pain and analgesia fluctuations. One method is to sum his total opioid use per day during the past several weeks and then convert to an equivalent dose of either methadone or SR morphine. Alternatively, an arbitrary dose, such as oral methadone 5 mg every 6 hours, could be started, and all of his current analgesics could be discontinued. If this dose is insufficient, a temporary dosage increase may be necessary. The long half-life of methadone will be beneficial when instituting opioid tapering.
Alternative analgesic adjuncts, such as antidepressants or anticonvulsants, should also be considered and introduced at this time. Opiate consolidation in W.C. would also serve to reduce his exposure to acetaminophen. He is currently taking three different acetaminophen-containing products. Although concern for opioid dosing emphasizes a balance between benefits and risks from the opioids, the risk of either short-term overdose or cumulative effects from acetaminophen (e.g., liver or renal toxicity) should not be overlooked. W.C. should be instructed not to exceed 4 to 5 g/day of acetaminophen from all sources, including analgesic and cold/sinus medications products he may be purchasing over the counter.
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