CYP3A activity in severe liver cirrhosis correlates with Child–Pugh and model for end-stage liver disease (MELD) scores
Impaired liver function often necessitates drug dose adjustment to avoid excessive drug accumulation and adverse events, but a marker for the extent of the required adjustment is lacking. The aim of this study was to investigate whether Child–Pugh (CP) and model for end-stage liver disease (MELD) scores correlate with drug clearance.
Midazolam was used as a CYP3A probe and its pharmacokinetics were analyzed in 24 patients with mild to severe liver cirrhosis (n = 4, 10 and 10 with CP class A, B and C, respectively) and six patients without liver disease.
Both scores correlated well with unbound midazolam clearance (CLu), unbound midazolam fraction and half-life (all P < 0.01), whereas the unbound steady-state volume of distribution was not significantly changed. In patients with severe liver cirrhosis unbound midazolam clearance was only 14% of controls (CP C: CLu = 843 ± 346 l h−1, MELD ≥ 15: CLu = 805 ± 474 l h−1, controls: CLu = 5815 ± 2649 l h−1, P < 0.01).
The correlation with unbound midazolam clearance suggests that either score predicts the metabolic capacity of CYP3A, the most relevant drug metabolizing enzyme subfamily in humans.