Euthyroxine has an effect on the heart. Euthyroxine, also known as levothyroxine sodium, is a common drug used to treat hypothyroidism. Hypothyroidism is a hypometabolic syndrome caused by the lack of thyroid hormone. The effects of hypothyroidism on the heart include slowed heart rate, low blood pressure, weakened myocardial contraction, etc. Serious cases can form pericardial effusion and hypothyroid heart disease. After eugenol replacement therapy, the above symptoms improve and heart function is restored. However, when the dose of eugenol is too high, it can cause drug hyperthyroidism and symptoms similar to hyperthyroidism, such as accelerated heart rate, increased systolic blood pressure, and even arrhythmia. Therefore, Eugenol has an effect on the heart, but the effect of Eugenol on the heart is produced by affecting the function of the thyroid gland. While taking Eugenol, there is no effect on the heart as long as the thyroid function is kept normal.