Protective effect of folinic acid on low-dose methotrexate genotoxicity

Methotrexate (MTX) is an antineoplastic agent widely used in low dose to treat patients with rheumatoid arthritis (RA). Its side effects can partly be explained by folate antagonism. Folinic acid (Leucovorin) is generally administered with MTX to decrease MTX-induced toxicity. However information regarding the inhibitory effect of folinic acid against cytogenetic damage caused by MTX is limited. The aim of this study was to assess the protective effect of folinic acid against MTX-genotoxicity. This study was done on Wistar albino rats and in patients with RA. Forty rats of both sexes were randomized into four equal groups and dosed in the following way: Group-I, distilled water vehicle; Group-II, 0.5 mg/kg folinic acid; Group-III, 0.5 mg/kg MTX; Group-IV, 0.5 mg/kg folinic acid plus 0.5 mg/kg MTX. Doses were given i.p., once daily for 8 consecutive days. A bone marrow chromosomal study and a micronucleus test were performed for each rat. Twenty patients with RA (5 males and 15 females) on a 10 mg weekly dose of MTX, i.m., for one month, were administered the same dose of MTX in addition to 10 mg of folinic acid as a single dose 4 hours after MTX administration, i.m., every week for another 4 weeks. Chromosomal studies as well as a micronucleus test were evaluated for each patient. MTX produced a significant genetic injury as proved by the increased incidence of chromosomal aberration and micronuclei formation in Group-III animals. Inversely, folinic acid (group IV) produced a significant protection against genetic damages induced by MTX. In RA patients, folinic acid provides satisfactory improvement of MTX-induced genetic damage. Folinic acid has a protective affect against MTX genotoxicity in human as well as in animal models.