RESUMO
BACKGROUND: For topically applied drugs such as 5-fluorouracil (5-FU), dosage is not as precise as for other drug administration pathways. Consequently, quantity of drug delivered may differ among individuals and applications. 5-FU is used in treatment of different diseases and has been reported as a clastogenic compound by micronucleus assay. METHODS: To determine whether 5-FU cream (5% 5-FU) absorbed through skin can produce genotoxic or cytotoxic effect in mouse bone marrow, induction of micronucleated erythrocytes (MNE) in mouse peripheral blood was examined after cutaneous application of 5-FU daily for 5 days. RESULTS: 5-FU cream induced significant micronuclei at doses of 37.5 mg (total weight of cream)/2 cm(2) and 75.0 mg/2 cm(2), as well as cytotoxic effects at doses of 150.0 and 300.0 mg/2 cm(2). CONCLUSIONS: Cutaneous application of 5-FU increased number of MNE in mouse peripheral blood. These data emphasize the importance of using correct dose when applying drugs topically.