Effect of Carrageenan-induced Acute Peripheral Inflammation on the Pharmacokinetics and Hepatic Metabolism of Midazolam in Rats

Abstract

The effect of carrageenan-induced acute peripheral inflammation (API) on the pharmacokinetics of the hepatically metabolizing compound midazolam (MDZ) was investigated in rats. Rats were subcutaneously treated with λ-carrageenan in the hind paw to induce API. When MDZ was intravenously administered in male rats, it was demonstrated that the plasma concentration profile of MDZ slightly alters in API rats compared with that in normal rats, while the plasma concentrations of its metabolites, 4-hydroxy and 1'-hydroxy MDZ, are markedly reduced with delayed appearances in API rats. In the incubation study with rat liver microsomes, it was clearly indicated that the generation rates of the two metabolites decrease in API rats. Western blot analysis revealed that hepatic CYP3A1 expression increases, while CYP3A2 expression decreases in API rats. In female rats, in which CYP3A2 is barely expressed in the liver, MDZ metabolism is little affected by API. These findings indicate that the hepatic handling of a therapeutic compound varies with API, largely due to altered hepatic expression of the drug-metabolizing enzyme.

Effects of dexamethasone to reverse decreased hepatic midazolam metabolism in rats with acute renal failure

“…MDZ was purchased from Sandoz (Tokyo, Japan) as a commercially available injectable solution in a sterilized isotonic buffer (pH 2.8-3.8). It was used without further purification (Hori et al, 2018;Kajikawa et al, 2014). Two MDZ metabolites, 4-Hydroxy MDZ (4-OH MDZ) and 1'-hydroxy MDZ (1'-OH MDZ), were obtained from BD Biosciences (San Jose, CA, USA) and Cerilliant (Round Rock, TX, USA), respectively.…”

“…The hepatic drug-metabolizing activity was evaluated focusing on CYP3A enzymes, in which NADPH-dependent MDZ elimination was examined in incubation experiments involving liver microsome preparations as previously reported with slight modification (Hori et al, 2018;Kajikawa et al, 2014). In brief, isotonic potassium phosphate buffer (pH 7.4) containing 200 µg of the microsomal protein was used as the incubation mixture.…”

“…The elimination rates of MDZ, and the formation rates of its two major metabolites, 4-OH MDZ and 1'-OH MDZ, were characterized with the Michaelis-Menten equation (Eq. 1) (Kajikawa et al, 2014):…”

“…Vmax is the maximum MDZ elimination rate, or the maximum formation rate of the metabolite. The parameter estimates were calculated with the non-linear least square method (Kajikawa et al, 2014). In this study, we considered that the MDZ elimination process is accounted for by the drug-metabolizing activities of CYP3A23/3A1 and 3A2 proteins, since it was demonstrated that the hepatic MDZ metabolism in rats is almost exclusively mediated by those two proteins, where the 4-OH MDZ formation is mainly mediated by CYP3A2 protein, while the 1'-OH MDZ formation was carried out by both CYP3A23/3A1 and 3A2 proteins (Kobayashi et al, 2002;Carr et al, 2006).…”

“…Hepatic drug metabolism decreases under the influence of impaired renal function, as demonstrated with the cytochrome P450 (CYP) 3A substrate midazolam (MDZ) in our previous study, in which the hepatic drug-metabolizing activity for MDZ decreased in rats with experimentally induced acute renal failure (ARF) as compared with control rats (Kusaba et al 2012). Propagation mechanism by which an influence of renal failure reaches the liver is not fully clarified to date, but inflammatory factors released into the circulatory system with impaired renal function seem to be partly involved in the decreased metabolism (Abdel-Razzak et al, 1995;Assenat et al, 2004;Kajikawa et al, 2014). Since the decrease in hepatic drug-metabolizing activity in ARF rats is largely due to decreased hepatic protein expression of CYP3A enzymes, it is considered that some processes of gene expression, such as transcription and translation, are impaired in ARF rats.…”