UI - 000162

AU - McQuay HJ

AU - Jadad AR

AU - Carroll D

AU - Faura C

AU - Glynn CJ

AU - Moore RA

AU - Liu Y

TI - Opioid sensitivity of chronic pain: a patient-controlled analgesia method

AB - Twenty-two patients with chronic pain of malignant or nonmalignant origin were given intravenous

morphine by patient-controlled analgesia. A prestudy judgment was made from the characteristics of the pain

as to whether it was nociceptive or neuropathic. Analgesic efficacy was assessed by a nurse-observer;

adverse events were noted and plasma morphine and metabolitie concentrations measured. Three categories

of opioid response were distinguished. Good responders obtained > 70 mm relief on the visual analogue

scale, with minimal or manageable adverse events. Moderate responders obtained < 70 but > 30 mm relief

with more problematic adverse events, and poor responders had < 30 mm relief with troublesome adverse

events. This method for the study of opioid sensitivity allowed a wide dosage range to be studied. The

simultaneous analgesic and adverse event measurements showed that the spectrum of observed response was

wide, and response category could be judged for the majority by 4 h. In those with poor or moderate

response, adverse event severity limited further dose increment. The relationship between pain

characteristics and response showed that some pains judged to be neuropathic had a good response to opioid

(5/13), and some pains judged to be nociceptive did not (5/14). The study suggests that the pattern of

response is not as black and white as the prediction of good response from nociceptive pain and poor from

neuropathic pain would suggest, although nociceptive pain was more likely than neuropathic pain to show a

good response. For the moderate responders opioid titration may, in the absence of other effective

treatments, be useful, but the analgesic endpoint may not be totally satisfactory. The method provides an

operational definition of opioid sensitivity.

SO - Anaesthesia 1992;47:757-76