This study aimed to evaluate some neurohumoral and hemodynamic alterations caused by chronic doxorubicin (DOXO) applications in the dog. These data could make easier the establishment of an early diagnosis of the toxicity caused by DOXO.

For such, 13 adult mongrel dogs, among males and females were used. Seven dogs received DOXO chloride (30mg/m², IV, 8 injections given each 21 days) and six, were given 0,9% NaCl solution (5mL, IV, 8 injections given each 21 days). During the experimental period, it was performed both electrocardiographic and echocardiographic evaluation, besides blood pressure assessment, determination of heart rate variability and plasma renin activity (PRA), measurement of plasma norepinephrine and plasma brain natriuretic peptide.

Results showed that animals that received DOXO had significant decrease on R wave amplitude (starting at 60mg/m²), on both shortening and ejection fractions (after 90mg/m²), besides an increase in PRA (after 120mg/m²) and in left ventricle systolic and diastolic diameters (after 180mg/m² and 210mg/m², respectively).

These data allowed concluding that the treatment of dogs with DOXO can lead to cardiotoxicity after the dose of 60mg/m² is reached. The echocardiography showed to be more sensible than the determination of PRA in the early detection of left ventricle dysfunction, which is secondary to the anthraciclinic toxicity. Moreover, dogs undergoing DOXO treatment can have different degrees of sensibility to the toxicity induced by this drug.