Biodistribution of intravenously injected [¹⁴C] doxorubicin and [¹⁴C] daunorubicin in mice: Concise communication

[¹⁴C] doxorubicin (adriamycin) and [¹⁴C] daunorubicin (daunomycin) are cardiotoxic antibodies used in cancer therapy. These drugs were examined as possible agents for the measurement of regional myocardial blood flow. The antibiotics were injected intravenously into mice, which were then killed after various intervals. At a chemical dosage of 0.5 mg per kilogram, the content of the heart never exceeded 0.60% of the administered dose for doxorubicin and 0.55% for daunorubicin. The cardiotoxic effect of these drugs, therefore, is probably related to a specific sensitivity of the heart, rather than to an avid uptake of the drugs by the cardiac muscle. Further studies seem warranted, using a lower chemical dosage and higher specific activity.