The Effects of Fentanyl on Hepatic Mitochondrial Function

BACKGROUND Remifentanil interferes with hepatic mitochondrial function. The aim of the present study was to evaluate whether hepatic mitochondrial function is affected by fentanyl, a more widely used opioid than remifentanil. METHODS Human hepatoma HepG2 cells were exposed to fentanyl or pretreated with naloxone (an opioid receptor antagonist) or 5-hydroxydecanoate (5-HD, an inhibitor of mitochondrial adenosine triphosphate (ATP)-sensitive potassium [mitoKATP] channels), followed by incubation with fentanyl. Mitochondrial function and metabolism were then analyzed. RESULTS Fentanyl marginally reduced maximal mitochondrial complex-specific respiration rates using exogenous substrates (decrease in medians: 11%-18%; P = 0.003-0.001) but did not affect basal cellular respiration rates (P = 0.834). The effect on stimulated respiration was prevented by preincubation with naloxone or 5-HD. Fentanyl reduced cellular ATP content in a dose-dependent manner (P <0.001), an effect that was not significantly prevented by 5-HD and not explained by increased total ATPase concentration. However, in vitro ATPase activity of recombinant human permeability glycoprotein (an ATP-dependent drug efflux transporter) was significantly stimulated by fentanyl (P = 0.004). CONCLUSIONS Our data suggest that fentanyl reduces stimulated mitochondrial respiration of cultured human hepatocytes by a mechanism that is blocked by a mitoKATP channel antagonist. Increased energy requirements for fentanyl efflux transport may offer an explanation for the substantial decrease in cellular ATP concentration.