Dextromethorphan (CAS: 125-71-3; Formula: C₁₈H₂₅NO; MW: 271.40) is a specialty chemical and active pharmaceutical ingredient (API) widely used in the manufacture of over-the-counter cough suppressants. It works by acting on the brain's cough center to reduce the urge to cough, making it effective for treating non-productive coughs associated with colds, flu, or other respiratory conditions. Beyond its use in cough syrups and lozenges, it is sometimes included in combination medications to address multiple cold symptoms simultaneously. In recent years, dextromethorphan has also been studied for its potential off-label uses, such as in the treatment of neurological conditions like pseudobulbar affect and as an adjunct in managing certain mental health disorders due to its effects on NMDA receptors and serotonin activity. However, its misuse or excessive intake can lead to serious side effects, emphasizing the importance of adhering to recommended dosages.