EQUIANALGESIC DOSE RATIO BETWEEN METHADONE AND OTHER OPIOID AGONISTS IN CANCER PAIN - COMPARISON OF 2 CLINICAL-EXPERIENCES/

Background. Oral methadone is considered to be a valid opioid analgesi c alternative to morphine and hydromorphone in treating cancer pain. H owever, the use of methadone could be complicated by the limited knowl edge of the equianalgesic dose/ratio with the other analgesic opioids when switching in tolerant patients. Patients and methods. In two Pall iative Care Units, data collected regarding 88 advanced cancer patient s with pain switched from different opioids to oral methadone were rev iewed and compared with the aim of determining the equianalgesic dose ratio in relation to the dose of opioid previously administered. Resul ts: The results of this retrospective study suggest that: (1) methadon e is much more potent than previously described in literature, (2) the dose ratio between hydromorphone and methadone is higher than as sugg ested by equianalgesic tables, and (3) the ratio correlates with total opioid dose administered before switching. Conclusions: The fact that methadone ratio is different according to the opioid dose used previo usly should be taken into careful consideration by the clinician in or der to avoid severe toxicity or death during switchover. Prospective s tudies should be carried out in order to better define our findings.