Prevention of Toxicity of Massive Doses of A-methopterin by Gitrovorum Factor. ∗

Abstract

Summary

1. The administration of citrovorum factor 15 minutes prior to seven to thirty times as large a dose of A-methopterin, prevented the toxicity of the antimetabolite at levels ranging from 2 to 100 times the chronic LD₅₀. 2. No significant protective effect was noted when similar dosages of citrovorum factor were given four or more hours after the administration of A-methopterin. 3. A-methopterin appears to be a true antagonist of citrovorum factor rather than of pteroylglutamic acid.