Effect of aqueous solution of stevioside on pharmacological properties of some cardioactive drugs.

BACKGROUND/AIM: Stevioside is a glycoside that supposedly possesses a number of pharmacodynamic effects such as anti-infective, hypoglycemic, along with the beneficial influence on the cardiovascular system. The aim of this study was to determine the effect of rats pretreatment with aqueous solution of stevioside on pharmacological actions of adrenaline, metoprolol and verapamil. METHODS: Rats were administered (intraperitoneally 200 mg/kg/day) stevioside as aqueous solution or physiological saline in the course of 5 days, then anaesthetized with urethane and the first ECG recording was made. The prepared jugular vein was connected to an infusion pump with adrenaline (0.1 mg/mL), verapamil (2.5 mg/mL) or metoprolol (1 mg/mL). Control animals, pretreated with saline, in addition to the mentioned drugs, were also infused with the solution of stevioside (200 mg/mL) in the course of recording ECG. RESULTS: The infusion of stevioside produced no significant changes in ECG, even at a dose exceeding 1,600 mg/kg. In the control group, a dose of adrenaline of 0.07 +/- 0.02 mg/kg decreased the heart rate, whereas in the stevioside-pretreated rats this occurred at a significantly higher dose (0.13 +/- 0.03 mg/kg). In stevioside-pretreated rats, the amount of verapamil needed to produce the decrease in heart rate was significantly lower compared to the control. The pretreatment with stevioside caused no significant changes in the parameters registered on ECG during infusion of metoprolol. CONCLUSION: The results suggest that pretreatment with stevioside may change the effect of adrenaline and verapamile on the heart rate.