The pharmacokinetics of midazolam in paediatric patients

Area of Science:

• Pharmacokinetics
• Pediatric Pharmacology
• Drug Metabolism

Background:

• Midazolam is a commonly used sedative in pediatric patients.
• Understanding its pharmacokinetic profile is crucial for safe and effective dosing.
• Variability in absorption and bioavailability across different routes necessitates detailed investigation.

Purpose of the Study:

• To characterize the serum concentration profile of midazolam in children aged 3-10 years.
• To compare the bioavailability and pharmacokinetic parameters of midazolam administered via intravenous, intramuscular, rectal, and oral routes.
• To assess dose-dependent bioavailability for the oral route and establish bioequivalence between specific routes.

Main Methods:

• A pharmacokinetic study involving 56 children aged 3-10 years.
• Administration of midazolam via intravenous, intramuscular, rectal, and oral routes at varying doses (0.15, 0.45, and 1 mg.kg-1).
• Serum concentrations were measured for 5 hours using gas-liquid chromatography.

Main Results:

• Key pharmacokinetic parameters: volume of distribution (Vss) of 1.29 l.kg-1, elimination half-life of 1.17 h, and serum clearance of 9.11 ml.kg-1.min-1.
• Peak serum concentrations were achieved at 15 min (intramuscular), 30 min (rectal), and 53 min (oral) for the 0.15 mg.kg-1 dose.
• Bioavailability: 87% (intravenous), 18% (intramuscular), 27% (rectal), and 87% (oral) at 0.15 mg.kg-1. Oral bioavailability decreased to 15% at higher doses.
• Bioequivalence was observed between the 0.15 mg.kg-1 intramuscular dose and the 0.45 mg.kg-1 oral dose from 45 to 120 min.

Conclusions:

• Midazolam exhibits route- and dose-dependent bioavailability in children.
• Intravenous administration provides the highest bioavailability, while oral and rectal routes show significantly lower absorption.
• The observed bioequivalence between intramuscular and a higher oral dose suggests potential therapeutic interchangeability under specific conditions.