At recommended doses, OTC cough medicines give you cough relief and have little or no physical or psychological side effects. When abused—sometimes at 25–50 times the recommended dose—dextromethorphan-containing cough medicines can cause strong visual hallucinations, mild distortions of color and sound, out-of-body sensations, confusion, slurred speech, or the loss of motor control. Other serious side effects can include:

• Delusions
• Panic attacks
• Memory problems
• Blurred vision
• Stomach pain, nausea, and vomiting
• High blood pressure and rapid heartbeat
• Numbness of fingers and toes
• Drowsiness and dizziness
• Fever and headaches
• Rashes and itchy skin
• Loss of consciousness

The effects can be worsened if the DXM-containing cough medicine being abused also contains other ingredients to treat more than just coughs or if it is being abused in combination with other medications, or taken with alcohol and illegal drugs.