Methotrexate and folic acid effect in normal and sarcoma 180 bearing mice.

Four- to six-fold surplus of folic acid in oral application reduced the toxicity of methotrexate administered repeatedly in high therapeutic doses. The therapeutic effect of methotrexate applied intraperitoneally to mice with the ascitic S 180 sarcoma, as measured by their survival, can be reliably demonstrated; moreover, the survival can be prolonged by adding folic acid into drinking water. In the solid form S 180 the intraperitoneal administration of methotrexate did not significantly reduce the weight of tumors of treated aminals as compared to untreated animals. The maximum tolerated dose of methotrexate was lower in animals with the ascitic tumor than in non-tumorous animals.