J. D. Borel

Age and fentanyl pharmacokinetics.

Fentanyl pharmacokinetics was compared in two groups of adult patients, one group (n = 5) aged <50 years, and one group (n = 4) aged > 60 years. Despite equivalent doses of fentanyl (10 μ/kg IV), serum drug concentrations were significantly higher in the older patient group. This was reflected by a prolonged terminal elimination half-life in the elderly compared with the younger patients (945 versus 265 minutes, respectively, p < 0.005). Volumes of the central compartment and volumes of drug distribution were similar in both patient groups. However, drug clearance was markedly decreased in the elderly (265 versus 991 ml/min, p < 0.005). These data suggest that a given dose of fentanyl will be clinically effective for a longer period in older patients than in younger patients.

Enflurane blood-gas solubility: influence of weight and hemoglobin.

The blood-gas partition coefficient of enflurane was measured in nine nonobese and eight morbidly obese patients and correlated with weight, body mass index, and blood hemoglobin. The enflurane blood-gas partition coefficient was lower in the obese patients than in nonobese patients (mean ± SEM: 2.03 ± 0.02 versus 1.76 ± 0.03, respectively, p < 0.025). There was a negative correlation between enflurane blood solubility and both body mass index and weight (r = −0.59 and −0.55, respectively, p < 0.01). A positive correlation was found between hemoglobin and the enflurane blood-gas partition coefficient (r = 0.69, p < 0.01). Equilibrium between inspired and alveolar enflurane concentration should be faster in morbidly obese and anemic patients than in healthy, nonobese patients.

Is Enflurane Defluorination Inducible in Man

Serum inorganic fluoride(F-) levels and anesthetic exposure were measured in 102 surgical patients to determine the effects of enzymeinducing drugs on enflurane metabolism. Serum electrolytes, urea nitrogen and creatinine values were also determined. Patients were classified into four groups according to their current drugintake histories:1)control(no drug), 26 patients;2)chronic ethanol, 31 patients;3)chronic phenobarbital and/or phenytoin, 12 patients; 4) miscellaneous drugs, 33 patients. None of the regression lines of peak serum F-on anesthetic exposure for the drug groups was significantly different from that of the control group. Five patients received enflurane anesthesia twice, with the regression line for the second exposure not significantly different from that for the first. Mean peak serum F-level for all patients was 17.7±0.8 μM, with the highest individual value in the study, 44.7μM, occurring in a control patient. Electrolyte, urea nitrogen, and creatinine values remained normal throughout the experiment. It is concluded that prior treatment with enzyme-inducing drugs does not increase enflurane defluorination in surgical patients, nor does it increase the risk of developing F- nephropathy.