Yes, Monocontin 25mg Tablet may affect the heart rate. Monocontin 25mg Tablet causes a decrease in blood pressure. This decrease in blood pressure further causes a decrease in the heart rate (bradycardia). In some cases, it may also cause an increase in the heart rate (tachycardia). Consult your doctor in case you do not feel well after taking this medicine or if you notice a change in your heart rate.