ABSTRACT
<b>Introduction:</b> The use of methadone in Japan is limited to cases being switched from the preceding use of strong opioids; the stop-and-go strategy is recommended in which the previously used opioid analgesic is discontinued and methadone is initiated at its full estimated dosage. <b>Case:</b> Refractory cancer pain due to an iliolumbar syndrome was temporarily exacerbated by the stop-and-go switching to methadone from morphine along with ketamine. Pain relief was achieved upon readministration and concomitant use of morphine with methadone after approximately two weeks. <b>Discussion:</b> Through examining this case, we believe that a stepwise switching strategy, rather than the stop-and-go strategy, could be more useful. Considering that overdosage may cause side effects, it is safer to initiate methadone with a small dose. However, more studies need to be conducted to decide whether the establishment of the initial dosage and dosage adjustment should be made more flexible to avoid pain intensification. Further investigation is required on whether the concomitant use of adjuvant analgesics such as ketamine, which similar to methadone is an NMDA receptor antagonist, should be continued when switching to methadone.