The effect of propofol on midazolam metabolism in human liver microsome suspension.

We have studied the inhibitory effects of propofol on the metabolism of midazolam using human liver microsomes. In addition, we also investigated whether the lipid in which propofol is solubilised inhibits the metabolism of midazolam. Only high concentrations of propofol (> 100 mmol), greater than those found in clinical practice, inhibited the metabolism of midazolam. The lipid had no effect on the metabolism of midazolam. This study differs from other laboratory studies looking at the inhibitory effects of propofol. These showed inhibition at concentrations similar to those seen in patients. The reasons for the differences may be explained by the use of different substrates or methodology. Propofol may be an enzyme inhibitor, but this remains to be shown to be important in patients.