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Clinical pharmacokinetics of methotrexate in children
Insights
Age significantly impacts how children and adults process methotrexate, affecting its toxicity. Further research is needed to understand methotrexate polyglutamate metabolism and its role in pediatric cancer treatment.
Area of Science:
- Pharmacology
- Pediatric Oncology
- Drug Metabolism
Background:
- Methotrexate is an antineoplastic agent with differing pharmacological profiles in children and adults.
- Age is a key determinant influencing both the pharmacokinetics and pharmacodynamics of methotrexate.
- Methotrexate pharmacokinetics directly correlate with its observed toxicity.
Purpose of the Study:
- To investigate the age-dependent differences in methotrexate handling in pediatric and adult populations.
- To explore the relationship between methotrexate pharmacokinetics, tissue distribution, and toxicity in children.
- To identify potential areas for further research, including the role of methotrexate polyglutamates.
Main Methods:
- Comparative analysis of methotrexate pharmacokinetics and pharmacodynamics across different age groups.
- Assessment of plasma drug concentrations and clearance rates.
- Evaluation of tissue distribution and drug turnover rates.
Main Results:
- Methotrexate clearance's beta-phase appears consistent across ages.
- Children exhibit increasing plasma methotrexate concentrations with age, with implications for the area under the concentration-time curve yet to be fully defined.
- Evidence suggests greater tissue distribution in children, potentially leading to increased toxicity, contrasted by observations of faster tissue turnover potentially limiting organ concentration.
Conclusions:
- Age-related differences in methotrexate pharmacokinetics and pharmacodynamics are significant in pediatric and adult patients.
- Increased tissue distribution in children may contribute to higher methotrexate toxicity.
- Further investigation into methotrexate metabolism, specifically methotrexate polyglutamates, is warranted to elucidate its biological effects and potential role in toxicity, particularly in the central nervous system.
Abstract:
Among the few antineoplastic agents investigated pharmacologically in children and adults, methotrexate has been clearly demonstrated to be handled differently in the two age groups. Age has in fact proved to be a major determinant, exerting an effect on both the pharmacokinetics and pharmacodynamics of methotrexate. Its pharmacokinetics, in turn, determine the drug toxicity. The beta-phase of methotrexate clearance, represented by the plasma drug concentration 48 hours from the start of a 6-hour infusion in a high dose treatment regimen, appears to be constant with age. In children, an increasing plasma drug concentration is apparent with increasing age, but whether this trend reflects a potential increase in the area under the plasma concentration-time curve of methotrexate has yet to be defined. Recent investigations have suggested that the drug is more completely distributed in the tissues of children than adults at the same infused dosage. This may explain the increased tissue toxicity caused by methotrexate. However, other observations suggest a faster drug turnover rate in the tissues of children. This may prevent the drug from concentrating in vital organs. Whether the metabolism of methotrexate, particularly the biosynthesis of methotrexate polyglutamates, plays a role in the biological effect of the drug is worthy of further investigation. The high brain tissue concentration after systemic methotrexate infusion and the slower efflux of methotrexate from brain tissues and cerebrospinal fluid make these tissues vulnerable to methotrexate toxicity.