Inflammation and Organ Failure Severely Affect Midazolam Clearance in Critically Ill Children.

Am J Respir Crit Care Med. 2016 Jan 21

AUTHORS: Vet NJ et al

RATIONALE:

Various in vitro, animal and limited human adult studies suggest a profound inhibitory effect of inflammation and disease on Cytochrome P450 3A (CYP3A)-mediated drug metabolism. Studies showing this relationship in critically ill patients are lacking, while clearance of many CYP3A drug substrates may be decreased, potentially leading to toxicity.

OBJECTIVES:

To prospectively study the relationship between inflammation, organ failure and midazolam clearance, as validated marker of CYP3A mediated drug metabolism, in critically ill children.

METHODS:

From 83 critically ill children (median age 5.1 months (range 0.02-202 months)), midazolam plasma levels (n=532), cytokines (e.g. IL-6, TNF-a), C-reactive protein (CRP) and organ dysfunction scores (PRISM II, PIM2, PELOD), as well as number of failing organs were prospectively collected. A population pharmacokinetic model to study the impact of inflammation and organ failure on midazolam pharmacokinetics was developed using NONMEM 7.3.

MAIN RESULTS:

In a two-compartmental pharmacokinetic model, body weight was the most significant covariate for clearance and volume of distribution. Both CRP and organ failure were significantly associated with clearance (p<0.01), explaining both inter-individual and inter-occasional variability. In simulations a CRP of 300 mg/L was associated with a 65% lower clearance compared to 10 mg/L and three failing organs were associated with a 35% lower clearance compared to 1 failing organ.

CONCLUSIONS:

Inflammation and organ failure strongly reduce midazolam clearance, a surrogate marker of CYP3A-mediated drug metabolism, in critically ill children. Hence, critically ill patients receiving CYP3A substrate drugs may be at risk of increased drug levels and associated toxicity.