What is the fine-grained topic of the following text: Even dextromethorphan, which is the active ingredient in most over-the-counter cough syrups, can cause major health problems, such as increased heart rate, fever and liver damage, when taken at sizzurp-levels, which can reach 25 times the recommended dose. Only return the topic.
Health risks of overusing dextromethorphan in cough syrups