Pharmacologic Treatment of Cancer Pain

Publisher Website
Google Scholar
Abstract
In his review of the treatment of cancer pain (Oct. 10 issue),1 Levy states that methadone is not recommended for routine (or initial) therapy. He goes on to state that an oral dose of 10 mg of methadone every six to eight hours is equivalent to 15 mg of morphine every four hours (Table 2 of the article). According to these recommendations, a patient receiving 150 mg of morphine every four hours would be switched to 100 mg of methadone every six to eight hours. This dose of methadone could result in severe sedation or respiratory depression in a patient already receiving morphine. We recently found that the potency of methadone relative to morphine in patients receiving long-term therapy is 5 to 10 times higher2,3 than is given above and in two reviews,4,5 whereas the ratio between hydromorphone and morphine is similar to that reported in Levy's Table 2. Moreover, the relative potency of methadone increased in relation to the duration of previous opioid treatment.5 The use of relatively higher doses of methadone appropriate for opioid-naive patients receiving long-term therapy with high doses of other opioids might explain the severe toxicity previously reported with methadone.5