Temporal changes in bupivacaine kinetics

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Abstract
The chronokinetics of bupivacaine have been examined in the mouse. Different groups of adult male NMRI mice maintained under controlled environmental conditions received a single intraperitoneal injection of bupivacaine (20 mg kg−1) at one of four different fixed time points in a 24 h period i.e. 1000, 1600, 2200 and 0400h. Blood samples were taken 0.25, 0.5, 0.75, 1, 1.5, 3, 4 and 6 h after drug administration and total serum levels of bupivacaine were determined by a gas-liquid chromatography with a flame ionization detector. Statistically significant temporal changes were found in the following pharmacokinetic parameters: highest Cmax value = 0.900 ± 0.080 μg mL−1 at 2200h (amplitude, maximum-minimum/mean × 100, is 64%); highest Cmax/Tmax ratio = 3.596 ± 0.339 at 2200h (amplitude = 85%); highest β elimination half-life, T½β;, = 3.950 ± 0.246 h at 2200h (amplitude = 35%); area under concentration curve (AUC0∞) was not found to be significantly different among the hours of administration. The temporal kinetic changes demonstrated suggest a possible circadian difference in bupivacaine efficacy and/or toxicity.