Cardioprotection by dexrazoxane in rats treated with doxorubicin and paclitaxel.

PURPOSE

Results of several clinical studies suggest that the combination of doxorubicin (DOX) and paclitaxel (PTX) is highly active against solid tumors. Both drugs are known to cause adverse cardiac effects, cardiomyopathy in the case of DOX and acute changes in cardiac rhythm in the case of PTX. It has been suggested that the addition of dexrazoxane (DZR) to this regimen may reduce the risk of cardiotoxicity. A model of chronic cardiomyopathy in the rat was used to determine whether DZR was tolerated and cardioprotective in a DOX + PTX combination.

METHODS

Male rats were treated once weekly for 7 weeks with one of the following vehicle and/or drug sequences: Group A, M/6 sodium lactate/saline/Cremophor EL (CEL); Group B, lactate/DOX/CEL; Group C, DZR/DOX/CEL; Group D, lactate/DOX/PTX; and Group E, DZR/DOX/PTX. DZR and DOX or their respective vehicles were given i.v. whilst PTX or CEL were given i.p. DZR, DOX and PTX were administered at 16 mg/kg, 0.8 mg/kg and 2.4 mg/kg, respectively, doses which caused minimal noncardiac toxicities. The hearts were examined histologically 5 weeks following the last treatment.

RESULTS

There were no deaths and no signs of overt toxicity during the 12 weeks of study. There was a significant decrease (P < 0.01) in white blood cell count in rats treated with DZR + DOX, DOX + PTX or DZR + DOX + PTX but not in those given DOX alone. Liver and kidney weights were increased in rats given DOX (P < 0.05) but not in those given DZR + DOX. PTX had no effect on the DOX-induced liver and kidney changes and did not interfere with the protective effect of DZR on the kidney. The severity and extent of cardiomyopathy expressed as the mean total score (MTS) for each treatment group, was similar for DOX and DOX + PTX (4.6 and 4.2, respectively). DZR provided significant cardioprotection (P < 0.01) when added to either DOX (MTS 2.0) or to DOX + PTX (MTS 2.1).

CONCLUSIONS

The results suggest that PTX does not exacerbate the chronic cardiomyopathy caused by DOX and when added to the DOX + PTX combination, DZR retains its protective activity against DOX-induced cardiotoxicity without increasing noncardiac toxicity.