© AEPress s.r.o. AIM: The present study aimed to determine the protective effect of melatonin and agomelatine on DOX-induced cardiotoxicity in rats by electrocardiographic, scintigraphic and biochemical methods. MATERIALS AND METHODS: Forty-nine male Wistar rats were randomly separated into seven groups; control (CON), doxorubicin (DOX), melatonin (MEL), agomelatine (AGO), melatonin+doxorubicin (MEL+DOX), agomelatine+doxorubicin (AGO+DOX) and melatonin+agomelatine+doxorubicin (MEL+AGO+DOX) groups. Cardiotoxicity was induced by intraperitoneal (i.p.) injection of DOX (18 mg/kg daily for three days). Rats receiving MEL and AGO treatment in the DOX-induced cardiotoxicity group received MEL and AGO (40 mg/kg/day, i.p., for seven days). They were injected with doxorubicin (18 mg/kg, i.p.) on days 5, 6, and 7. The rats were given MEL and AGO as substance control (40 mg/kg/day, i.p., for 7 days). On day 8 of the experiment, animals were evaluated by means of electrocardiography (ECG) and 99m technetium pyrophosphate ( 99m Tc PYP) scintigraphy and their biochemical parameters [blood urea nitrogen (BUN), creatine kinase (CK), cardiac troponin T (cTnT)] were examined. RESULTS: DOX-induced acute cardiotoxicity in rats is characterized by conduction abnormalities in the ECG pattern (including decreased P wave and QRS complex duration, increased QT and RR intervals, and STsegment elevation), increased serum BUN, CK, and cTnT parameters and increased 99m Tc PYP uptake (p < 0.001). Pretreatment with MEL, AGO, or MEL+AGO effectively alleviated DOX-induced ECG abnormalities close to normal (p < 0.001). Moreover, serum biochemical evidence and 99m Tc PYP uptake values demonstrated that pretreatment with MEL, AGO, or MEL+AGO has the same protective effect against the abnormalities produced in the heart by DOX (p < 0.001). CONCLUSIONS: MEL and AGO have a potential protective effect on DOX-induced cardiotoxicity. At the same time, this study suggests that 99m Tc PYP is a non-invasive method suitable for early determination of DOX-induced cardiotoxicity.