Dextromethorphan is a pharmaceutical that suppresses the urge to cough. It is a common ingredient in most over-the-counter cough medicines. It is a white powder in its pure form, but is usually added to a syrup, lozenge or spray. Unlike other cough suppressants, like codeine, it is not addictive and has no sedative effect. However, although not addictive, it can cause psychological dependence.
However, Dextromethorphan can be abused recreationally as it causes dissociative hallucinations in higher doses. It was originally sold in pill form, but due to the risk of abuse, it is generally not sold in that form any longer.
Dextromethorphan has limited side effects, but should not be used with infants due to the risk of sudden infant death syndrome. It can cause nausea, drowsiness and dizziness with therapeutic doses. In larger doses, there are risks of vomiting, dilated pupils, sweating, fever, high blood pressure and diarrhea. It is contraindicated in children with allergies and in patients who take mood altering drugs such as MAOIs or SSRIs.
In Ignorance is Bliss, House discovers his genius patient James Sidas has been abusing dextromethorphan to reduce his intelligence and has avoided permanent brain damage by using alcohol in moderation.