Dextromethorphan, the active ingredient in over-the-counter cough and cold medications, may be used as a drug of abuse, particularly by adolescents. According to a 2006 study by the Partnership for a Drug Free America, 1 in 10 teens admitted to using dextromethorphan (DXM) to get high, leading to monitoring of DXM availability by the United States Department of Justice and a June 2009 congressional amendment proposing its inclusion in the National Controlled Substance Act. The effects of DXM on the brain are dose dependent and may also be influenced by other drugs a person is taking, or the vehicle used to provide DXM.
DXM Intoxication
The symptoms of DXM intoxication are described in terms of four dose-dependent phases. Phase 1 DXM ingestion (1.5 to 2.5 mg/kg) is associated with increased alertness, enhanced visual and auditory sensitivity and a sense of generalized euphoria similar to alcohol intoxication. Phase 2 DXM ingestion (2.5 to 7.5 mg/kg) produces increased energy and excitability, hallucinations and loss of balance. Periods of exaggerated sensitivity to visual and auditory stimuli may alternate with periods of relative deprivation, and patients may lose their sense of balance. Individuals commonly describe a feeling of disassociation or "out of body" experience comparable to the effects of phencyclidine (PCP) or the animal tranquilizer ketamine ("Special K").
At Phase 3 (7.5 mg/kg to 15mg/kg), significantly impaired cognition, delayed reaction and response time, severe visual/auditory disturbances, mania or panic are characteristic. Signs of Phase 3 ingestion includes partial consciousness, dilated pupils and "nystagmus," which is markedly abnormal, jittery movements of the eyes. People exhibiting these symptoms should be taken to the emergency room immediately. It may be difficult to distinguish Phase 4 ingestion (greater than15 mg/kg) from Phase 3. In Phase 4, the individual may be unable to walk or exhibit any coordinated movement; hallucinations and delusions are severe. Although DMX abuse is rarely fatal, five deaths have been reported among those with Phase 4 ingestions.
Serotonin Syndrome
DXM is a weak activator of the serotonin-signaling pathway in the brain. At DXM doses over 7.5 mg/kg--or in people who are also taking the antibiotic linezolid or certain kinds of antidepressants called selective serotonin reuptake inhibitors (monoamine oxidase inhibitors)--a potentially fatal condition called serotonin syndrome may result. Signs of serotonin syndrome include altered mental status, fever, stiffness or muscular rigidity, and seizures. People exhibiting signs of serotonin syndrome must be taken to the emergency room immediately.
Bromism
Most DXM in over-the-counter medications is supplied as dextromethorphan-bromine. Bromine can accumulate in the body, causing a syndrome known as bromism. Symptoms of bromism include lethargy, irritability and behavioral changes. There is no antidote for bromine toxicity. Care is supportive, including hydration and--in severe cases--hemodialysis.
References
- United States Department of Justice National Drug Information Center
- Journal of the American Pharmacy Association. Dextromethorphan abuse: clinical effects and management. Romanelli F, Smith KM. March-April 2009.
- Addiction Biology. Dextromethorphan psychosis, dependence and physical withdrawal. Miller SC. December 2005.
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