Pharmacokinetic interaction between methotrexate and chloral hydrate

Area of Science:

• Pediatric Oncology
• Clinical Pharmacology
• Drug Interactions

Background:

• High-dose methotrexate (MTX) is a cornerstone in treating acute leukemia.
• Chloral hydrate (CH) is sometimes used for sedation in pediatric patients undergoing chemotherapy.
• Understanding potential drug interactions is crucial for optimizing treatment efficacy and safety.

Observation:

• A case study involving a child with acute leukemia revealed an unexpected drug interaction.
• The patient received high-dose MTX chemotherapy concurrently with CH for sedation.
• Renal function, hydration, and urine alkalinization were monitored and deemed adequate.

Findings:

• Co-administration of CH with high-dose MTX led to significantly reduced MTX clearance.
• MTX exposure, measured by area under the curve (AUC), was substantially higher (1,134 µmol·h/L) during CH use compared to when CH was discontinued (608 µmol·h/L).
• This interaction occurred despite normal renal function, adequate hydration, and urine alkalinization.

Implications:

• The findings suggest a potential pharmacokinetic interaction between CH metabolites and MTX.
• Competition for renal tubular secretion pathways may be the mechanism behind the reduced MTX clearance.
• This interaction highlights the need for careful consideration of concomitant medications, like CH, in pediatric patients receiving high-dose MTX chemotherapy.