Relationship between blood XXXX concentrations and analgesic response: a preliminary report.

@entity1 @entity6882 @entity806 @entity158 @entity663
Variability in analgesic responses to intramuscularly administered @entity6882 has been related to variable and unpredictable blood concentrations after injection. However, the contribution of variability in the relationship between blood concentration and effect has not been examined. The present study was designed to determine the relationship between blood @entity6882 concentrations and analgesic effects in nine @entity1 during the first two postoperative days. @entity158 was estimated by subjective bioassay. The blood concentration-effect curves were steep, with a difference of as little as 0.05 microgram/ml between the mean concentrations associated with severe @entity158 and those associated with effective analgesia. Each curve had two inflection points: the maximum concentration still associated with severe @entity158 ( @entity806 ) (0.41 microgram/ml, SD = 0.17, n = 76) and the minimum effective analgesic concentration (MEAC) (0.46 microgram/ml, SD = 0.18, n = 19). Interpatient variability of MEAC was appreciable (coefficient of variation = 39 percent) and intrapatient variability was also detected. Variable @entity158 control following intermittent intramuscular injections was shown to be due not only to variation in absorption, as reported previously, but also to variation in the blood @entity6882 concentration-analgesic response relationships. However, correlations were found between @entity806 and @entity663 and extroversion scores from a personality inventory and physical variables. Thus, equations that allow prediction of an individual's @entity806 were derived by multivariable regression. A blood @entity6882 concentration of 0.7 microgram/ml would be expected to provide freedom from severe @entity158 in approximately 95 per cent of cases. An intravenous infusion regimen for achieving and maintaining this concentration is described.
