What is the purpose for determining serum concentrations of the antineoplastic drug methotrexate?

What is the purpose for determining serum concentrations of the antineoplastic drug methotrexate?

• A. To ensure that serum concentrations are in the therapeutic range
• B. To ensure that serum concentrations are not in the toxic range
• C. To determine the amount of leucovorin needed to halt methotrexate action
• D. All of these

Answer: (D)

Measuring serum methotrexate levels is part of therapeutic drug monitoring for this drug. The goal is to keep drug concentrations within a range that is high enough to kill cancer cells but low enough to avoid unacceptable toxicity. By checking levels at specific times after infusion, clinicians can judge how quickly the patient is clearing the drug and tailor supportive care accordingly. Leucovorin rescue is adjusted based on these levels: higher or more persistent methotrexate concentrations require more leucovorin to protect normal tissues while preserving antineoplastic effect. Hydration and other supportive measures are also guided by the measured levels. Because monitoring serves to maintain efficacy, prevent toxicity, and tailor leucovorin rescue, this comprehensive approach is the best description of the purpose.

Measuring serum methotrexate levels is part of therapeutic drug monitoring for this drug. The goal is to keep drug concentrations within a range that is high enough to kill cancer cells but low enough to avoid unacceptable toxicity. By checking levels at specific times after infusion, clinicians can judge how quickly the patient is clearing the drug and tailor supportive care accordingly. Leucovorin rescue is adjusted based on these levels: higher or more persistent methotrexate concentrations require more leucovorin to protect normal tissues while preserving antineoplastic effect. Hydration and other supportive measures are also guided by the measured levels. Because monitoring serves to maintain efficacy, prevent toxicity, and tailor leucovorin rescue, this comprehensive approach is the best description of the purpose.