Sources of variation in analgesic responses in cancer patients with chronic pain receiving morphine

Our objective was to identify and quantify sources of variation in the relief of chronic pain with morphine. Relief scores were extracted from records obtained during controlled trials of analgesics in cancer patients with chronic pain in which intramuscular morphine was the assay standard. Relief data from 715 patients after 565 8-mg and 538 16-mg doses were segregated according to age, race, sex, pre-drug pain intensity, character and site. Middle-aged patients obtained relief after 8 mg comparable to relief obtained by younger patients after 16 mg; oldest patients obtained relief after 8 mg comparable to relief obtained by middle-aged patients after 16 mg. Blacks receiving 8 mg obtained relief comparable to whites receiving 16 mg. Sex-related differences were not significant. Patients with moderate, as compared to severe, pre-drug pain obtained significantly greater relief only after 16 mg. Patients reporting dull pain obtained relief after 8 mg comparable to relief obtained with sharp pain after 16 mg. Patients with abdominal pain obtained relief after 8 mg comparable to relief of pain in the chest or arms after 16 mg. These results provide dose-related evidence of variation in relief with morphine in chronic cancer pain and establish particular patient and pain characteristics as variables for which controls should be provided in analgesic assays.