ANALGESIC STUDIES OF CODEINE AND OXYCODONE IN PATIENTS WITH CANCER .1. COMPARISONS OF ORAL WITH INTRAMUSCULAR CODEINE AND OF ORAL WITH INTRAMUSCULAR OXYCODONE

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  • 1 January 1978
    • journal article
    • research article
    • Vol. 207  (1) , 92-100
Abstract
The relative analgesic potency of oral and i.m. codeine was evaluated in a double-blind crossover comparison of graded single doses in patients with chronic pain due to cancer. When both duration and intensity of analgesia were considered (total effect), oral codeine was 6/10 as potent as the i.m. form. This was a high oral/parenteral analgesic relative potency ratio compared with morphine, metopon and oxymorphone and correlated well with the results of recent studies which have determined the oral vs. i.m. bioavailability of codeine in man. Oral and i.m. oxycodone were also compared in a similar patient group. Like codeine, oxycodone retained at least 1/2 of its analgesic activity when administered orally. The high oral/parenteral relative potency ratios of codeine and oxycodone relative to morphine and its congeners may not be due to more efficient absorption after oral administration, but rather that methylation at position 3 in codeine and oxycodone protects these drugs from rapid first-pass metabolism.