Determination of the LD50 of acridine orange via intravenous administration in mice in preparation for clinical application to cancer therapy.

AIM We undertook studies to determine the lethal dose 50 (LD50) of acridine orange (AO) using mice in order to confirm the safety of intravenous administration of AO. MATERIALS AND METHODS We used 40 mice and AO was administered once intravenously. General behavior and mortality were continuously observed for 14 days. At the end of the experiment, all animals were sacrificed for subsequent studies. RESULTS The LD50 for AO in male and female mice was determined to be 32 mg/kg and 36 mg/kg, respectively. Histopathological abnormalities were observed in only one mouse which died three days after the administration of AO. The other nine mice which died immediately after the administration of AO had no pathological findings in major organs. CONCLUSION The clinical use of AO can be kept at 1.0 mg/kg or below and, therefore, intravenous administration of AO might be safe for use as cancer therapy.