Clinical pharmacokinetics of methotrexate in the treatment of acute lymphoblastic leukemia and non-Hodgkin lymphoma in pediatric patients

Abstract

High dose methotrexate (MTX) is used in therapy of acute lymphoblastic leukemia and non-Hodgkin lymphoma in pediatric patients. It acts as competitive inhibitor of dihydrofolate reductase and consequently inhibits synthesis of deoxyribonucleic acid. The bioavailability is dependent upon dose and route of administration. The drug is moderately bound to plasma proteins and distributes in body tissues and cells. After the administration in high doses, MTX partially undergoes hepatic and intracellular metabolism, but renal excretion of parent compound is the main route of elimination. Numerous factors may influence pharmacokinetics and concentration of drug, but primarily the effect of renal function on elimination is described. Delayed elimination might also be the consequence of drug interaction in renal tubules. Toxicity can arise with high MTX doses, especially in patients with delayed MTX elimination. Therapeutic drug monitoring is indicated due to safety reasons, in order to optimize leucovorin (folinic acid) administration as it reduces MTX toxicity. Considering the variability and the toxicity of high dose MTX therapy, special caution is required in pediatric patients.

Metotreksat (MTX) se u visokim dozama koristi u terapiji akutne limfoblastne leukemije i ne-Hodkinovog limfoma u pedijatrijskoj populaciji. Deluje kao kompetitivni inhibitor dihidrofolat reduktaze i time inhibira sintezu dezoksiribonukleinske kiseline. Stepen biološke raspoloživosti zavisi od puta primene leka i doze. Vezivanje za proteine plazme je u umerenom stepenu, a raspodeljuje se u tkiva i ćelije. Nakon primene u visokim dozama MTX delimično podleže hepatičkom i intracelularnom metabolizmu, ali glavni put eliminacije je preko bubrega u nepromenjenom obliku. Veliki broj faktora utiče na farmakokinetiku i koncentraciju leka, a pre svega je opisan uticaj funkcije bubrega na eliminaciju. Usporena eliminacija može biti i posledica interakcije sa drugim lekovima na nivou transportera u renalnim tubulima. Primena visokih doza MTX nosi rizik od pojave toksičnosti, posebno pri usporenoj eliminaciji. Terapijsko praćenje leka je indikovano iz bezbednosnih razloga, kako bi se optimizovala primena leukovorina (folinska kiselina) koji smanjuje toksičnost MTX. Imajući u vidu varijabilnost i toksičnost pri primeni visokih doza MTX poseban oprez je potreban u pedijatrijskoj populaciji pacijenata.