Instructions before use: Have an electrocardiogram (routine) or/and cardiac ultrasound (routine). Exclude arrhythmias, severe conduction block, congenital heart disease and other disorders. Contraindications: Contraindications to the use of atenolol include cardiac lesions (conduction block) such as sinus tachycardia, atrioventricular block, heart failure, etc. Dosage: 0.5 mg/kg/day orally 1-2 times a day for the first week; thereafter, 1 mg/kg/day orally 1-2 times a day according to the child’s weight change. How to administer the medication: 10-15 minutes after breastfeeding, crush the tablet, put it in a spoon, dissolve it in 10mL of sugar water or milk water (milk powder) and pour it into the mouth at once. If the infant does not cooperate in spitting out the medicine, try to take a refill according to the dosage. Atenolol should be taken during the day after eating. Taking the drug after eating can help to avoid hypoglycemia. The plasma half-life after oral administration of atenolol is 6-8 h. Note to parents: Unlike propranolol, atenolol is a selective β1 receptor blocker with only a mild β2 receptor blocking effect, so its discomfort is less common than propranolol. Complications such as diarrhea, hypotension, bradycardia, and hypoglycemia are rare. In severe diarrhea, the drug needs to be stopped and taken again after the symptoms have completely disappeared and adapted. Hypotension and bradycardia generally have no subjective symptoms and do not require treatment. Regular monitoring of blood glucose is required. Blood glucose should be rechecked after 1 week of medication and every 1-2 months thereafter, and once hypoglycemia occurs, the medication should be stopped immediately. During the treatment period, vaccinations can be received normally. For other special cases, follow-up is required at any time. Post-treatment response: Atenolol has a slower onset of action compared to propranolol, and the tumor tends to change insignificantly early after taking the drug. After 1-2 months of oral administration of atenolol, the tumors begin to lighten in color, shrink and become softer. After 3 months of treatment, most of the tumors shrink significantly. By the age of 1 year, the tumor is largely receding, but capillary dilatation may remain on the surface. Significant changes are seen at 6 months after treatment. Duration of treatment: Medication must be continued for at least 6 months, as premature discontinuation can lead to rebound. Discontinuation criteria: complete regression of the hemangioma, or age over 1 year, end of the proliferative phase of the hemangioma. Taking medication in strict accordance with the doctor’s prescription, except for the occurrence of serious complications or other systemic diseases, and not reducing or stopping medication without authorization are crucial to avoid recurrence or rebound. Discontinuation method: halve the number of times in the first 2 weeks, halve the dose in the last 2 weeks, and stop the medication. Observe for 1 month and complete discontinuation if there is no rebound; if rebound, continue the drug for 1 month or longer according to the original regimen. Safety: Studies have confirmed that atenolol does not cross the blood-brain barrier, does not affect neurodevelopment in children, and usually has no effect on sleep in affected children. Respiratory side effects are rare due to the minimal beta2-blocking effect of atenolol.