Dextromethorphan is a common cough suppressant found in many over-the-counter cold and cough medications. It works by affecting the signals in the brain that trigger the cough reflex, helping to reduce the urge to cough. While generally safe when used as directed, misuse of Dextromethorphan can lead to serious side effects, including hallucinations and increased heart rate. It is important to follow dosage instructions and consult a healthcare professional if you have any concerns or underlying health conditions.