Teratological evaluation of 5-fluorouracil and 5-bromo-2-deoxyuridine on hamster fetuses.

A single intraperitoneal injection of 5-bromo-2-deoxyuridine (BUDR) between days 9 and 11 and a single intramuscular injection of 5-fluorouracil (FU) between days 8 and 11 of gestation were teratogenic in hamster. The malformation frequencies were related to the dose and time of BUDR and FU treatment but the pattern and types of malformations and their frequencies were different. BUDR showed lower embryotoxic effect than FU. Both drugs impaired general fetal growth. It is suggested that the differences between FU and BUDR may be related to the chemical nature and metabolism of the drug and their eventual effect on the species-specific target tissue.