DISAPPEARANCE OF MORPHINE-INDUCED HYPERALGESIA AFTER DISCONTINUING ORSUBSTITUTING MORPHINE WITH OTHER OPIOID AGONISTS

Hyperalgesia and allodynia in 4 cancer patients treated with morphine disappeared after discontinuing or substituting morphine with other op ioid agonists. The first case describes a young female who developed h yperalgesia and myoclonus during intravenous morphine infusion. The hy peralgesia and myoclonus disappeared when the morphine administration was discontinued and she felt comfortable on small and sporadic oral d oses of methadone. The second case describes hyperalgesia occurring af ter a small dose of sustained-release morphine which disappeared after alternative use of oral ketobemidone. The third case describes hypera lgesia following high doses of intramuscular morphine which disappeare d after alternative use of continuous subcutaneous infusion of sufenta nil. The fourth case describes a boy developing hyperalgesia after hig h doses of oral and intramuscular morphine. The hyperalgesia disappear ed after discontinuing morphine administration but withdrawal symptoms developed due to too small doses of methadone. Possible mechanisms of morphine-induced hyperalgesia are discussed.