The aim of this study was to explore the effects of the antihistamines (Astemizole, Loratadine and Cinnarizine), antimalarials (chloroquine phosphate and mefloquine HCI) and some medicinal plants (the aqueous extract of Cydonia oblongata and Licorice and alcoholic extract of olive oil) on cardiac muscle conductivity, contractility and coronary blood flow. In addition to using digoxin, nitroglycerine & adrenaline as comparative agents in this study. This study was performed by using 65 local domestic rabbits of both sexes. The cardiac conductivity was looked for by taking frequent ECG records to the involved rabbits in vivo while the cardiac muscle contractility and the coronary blood flow were measured in vitro. This in vitro test was accomplished by using Langendroff set which contains the isolated rabbit's heart linked to a multitrace grapher by a mechanical transducer to measure the cardiac muscle contractility and the coronary blood flow. These in vivo and in vitro parameters were taken for each tested agent and compared with the control group. Regarding the cardiac conductivity: both astemizole and chloroquine phosphate prolonged PR-interval significantly, astemizole, loratadine and mefloquine HCI decerased the heart rate significantly while the aqueous extract of licorice increased the heart rate. Both extracts of cydonia oblangata and licorice increased the R-amplitude significantly. In regard to the cardiac muscle contractility, both extracts of Cydonia oblongata and Licorice significantly increased the cardiac muscle contractility. Whereas the extracts of C. oblongata, Licorice and olive oil caused a significant increase in the coronary blood flow.