If a patient is taking a drug like digitalis before, for example, the patient is taking digoxin or applying trichothecene C, which is often referred to as cidilan, the patient is advised to have an electrocardiogram. This is because if the patient has a high degree of atrioventricular block, he or she should not use drugs like digitalis. If the patient has hypertrophic obstructive cardiomyopathy, digitalis should not be used in such patients, and in some patients, digitalis is also prohibited in the early stages of acute myocardial infarction. For people with simple mitral stenosis, it is also a contraindication to taking digitalis. In addition to this, patients are advised to have their serum ion and kidney functions checked. This is because digitalis should be used with caution in patients with hypokalemia and renal insufficiency, especially when the serum K ion concentration is low, and the drug digitalis should not be applied for the time being.