where the range for rescue by folic acid was fairly narrow and highly dependent on the timing (optimal of 1 hour prior to aminopterin) of administration in relation to aminopterin. The temporal relationship between folic acid administration and rescue has been interpreted as the necessary period of time required for the vitamin to be converted in vivo to reduced forms. References Antifolates Benzamides Mammalian dihydrofolate reductase inhibitors Veterinary toxicology Folates