Patient-controlled Analgesic Therapy, Part II

Abstract

20 survival patients were allowed to self-administer small intravenous doses of pethidine to relieve pain after major abdominal surgery. Pethidine injections were given by means of a programmable drug injector. Pethidine consumption varied from 12 to 50mg/h with a mean +/- SD of 26 +/- 10mg/h. The mean measured plasma concentration of pethidine during self-administration was 551 +/- 182 ng/ml, with a range of 132 to 896 ng/ml. Minimum effective concentrations averaged 455 +/- 174 ng/ml. Individual pethidine consumption and mean plasma concentrations did not differ between men and women, and were not correlated to variations in age, anthropometric factors, plasma clearance or elimination rate constant for pethidine. Individual consumption of pethidine was consistent, with stable plasma concentrations throughout most of the trial period. Pseudo-steady-state plasma concentrations of pethidine were established and maintained at widely different levels. 19 of the 20 patients obtained subjectively satisfactory analgesia.

Morphine Sulphate Slow Release

“…Individual patients request additional doses of analgesia when the plasma concentration of opioid decreases below MEAC. Although this is a relatively constant value for the individual, there is a five-fold variation between individuals (Tamsen et al, 1982). In the present study, there was a considerable difference between the mean serum concentrations of morphine in the two groups at 08.00 h and yet the levels of analgesia were similar -that in the MST group (at 08.00 h) being comparable to analgesia provided by i.m.…”

“…With patient controlled administration, a correlation has been demonstrated between plasma opioid concentration and effective analgesia (mean effective analgesic concentration or MEAC) (Tamsen et al, 1982). Individual patients request additional doses of analgesia when the plasma concentration of opioid decreases below MEAC.…”

Chronic pain alters drug self-administration: Implications for addiction and pain mechanisms.

“…The guiding principles for currrent PCA use and refinement were largely developed from the work of Austin and colleagues (1980), demonstrating the relationships between dosing intervals, plasma concentrations, and pain scores in post-operative patients. Similar studies have been conducted for a number of opioids and provide the basis for their successful use with PCA technologies (Dahlstrom et al, 1982; Tamsen et al, 1982; Lehman et al, 1988, 1991). …”