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American Society for Action on Pain

UI - 000077

AU - Lipman JJ

AU - Blumenkopf B

TI - Comparison of subjective and objective analgesic effects of intravenous and intrathecal morphine in chronic pain patients by heat beam dolorimetry

AB - The pain tolerance latencies of 10 chronic pain patients were evaluated by heat beam dolorimetry

(stimulus intensity 15.33 mW.cm-2.sec-1) prior to and following administration of morphine by intrathecal

(n = 5) or intravenous (n = 5) routes. Patients not undergoing opiate withdrawal evinced increased baseline

pain tolerance latencies prior to drug administration compared with normal volunteers. Two patients

undergoing the opiate withdrawal syndrome at the time of test experienced reduced pain tolerance latencies

compared with normal volunteers, most probably corresponding to the hyperesthesia symptom of the

syndrome. Intravenous morphine infusion (30 mg) induced a time-dependent increase in cutaneous pain

tolerance with peak effect occurring 1-2 h after administration. This persisted for up to 4 h and thereafter

declined. The time course of subjective pain self-report by visual pain analog scale (VPAS) measurements

corresponded to the time course of increasing cutaneous pain tolerance latency assessed by dolorimetry.

Pain self-reports following intrathecal morphine infusion (2.25 or 1 mg) followed a similar though slower

onset to that reported by patients receiving intravenous morphine and was of lesser degree. In contrast, heat

beam dolorimetric evidence of increased cutaneous pain tolerance (which was of lesser degree than

following i.v. morphine) did not reach its maximum during the 4 h measuring period. A dissociation was

noted therefore between the self-reported relief of endogenous pain and dolorimetrically measured

cutaneous analgesia following intrathecal morphine administration. Linear regression correlation analysis

characterized this phenomenon as a positive correlation between cutaneous pain tolerance and pain relief

self-report following intravenous morphine infusion and a negative correlation following intrathecal

administration. We propose that the phenomenon may be due to intrathecal morphine acting via two

separate compartments: one spinal and one supraspinal.(ABSTRACT TRUNCATED AT 250 WORDS)

SO - Pain 1989;39:249-25