Dextromethorphan for pain and cough suppression by Ray Sahelian, M.D.
June 11 2015

Dextromethorphan is an ingredient found in over-the-counter cough medicines and is often recommended for cough suppression but may not work that well.

Dextromethorphan drug abuse
Reports of dextromethorphan abuse to a California poison control hotline rose 10-fold from 1999 to 2004, and cases involving teens rose 15-fold, Dr. Jodi K. Bryner of the University of California at San Francisco and colleagues report. While the use of illegal drugs like LSD and Ecstasy has fallen among adolescents in recent years, over-the-counter drug abuse has been on the rise since the late 1990s. Coricidin HBP Cough & Cold Tablets is the product most commonly reported to California Poison Control System, followed by Robitussin. Dextromethorphan tablets appear to be more popular due to widespread over-the-counter availability, high dextromethorphan content, and palatability of the tablet formulation. Archives of Pediatrics and Adolescent Medicine, December 2006.

The U.S. Food and Drug Administration said in 2010 it would call on a panel of outside advisers to look at the potential risks and benefits of the drug dextromethorphan, used in cough medicines made by Pfizer Inc and Procter & Gamble Co, among others. Cough medicines have been under FDA scrutiny for the last few years, especially their use in children. The agency has said they should not be used in children 2 and younger, while manufacturers have urged against their use in children under 4.

PLoS One. 2014 Feb 28. Involvement of Sigma-1 Receptors in the Antidepressant-like Effects of Dextromethorphan. This is one way it may influence mood.

Dextromethorphan does not enhance morphine effect
Dr. Deborah J. Dudgeon of Queen's University in Kingston, Ontario, led a multicenter study of 65 patients with advanced cancer or chronic severe pain requiring 12-hour, slow-release morphine. Patients were randomly assigned to slow-release morphine plus either placebo or dextromethorphan, 60 milligrams four times a day for seven days. Dextromethorphan was then increased to 120 milligrams four times a day for another seven days, if the patient could tolerate it. There was no significant reduction in pain scores. Journal of Pain and Symptom Management, 2007.

Side effects
Serious side effects can occur if dextromethorphan is used with MAO inhibitor medications.

Dextromethorphan and serotonin syndrome
Dextromethorphan-induced serotonin syndrome.
Clin Toxicol (Phila). 2008. University of Pittsburgh, Division of Medical Toxicology, UPMC Presbyterian, Pittsburgh, Pennsylvania 15213, USA.
The ability of dextromethorphan to potentiate serotonin levels and lead to serotonin syndrome is well known but few case reports are published. The lack of published cases suggests therapeutic doses of these drugs are not enough to cause serotonin syndrome. We present two cases of serotonin syndrome associated with supra-therapeutic doses of dextromethorphan and therapeutic levels of a selective serotonin reuptake inhibitors (SSRI). In case one, serum drug levels from admission revealed a dextromethorphan level of 950 ng/mL (normal < 5), escitalopram of 23 ng/mL (normal < 200), chlorpheniramine of 430 ng/mL (normal < 20) and undetectable levels of aripiprazole and benztropine. In case two, serum drug levels from admission revealed a dextromethorphan level of 2820 ng/mL, sertraline of 12.5 ng/mL (normal < 200), and caffeine of 1.4 microg/mL (normal < or = 9 microg/mL). To our knowledge, these are the first cases to use serum levels of dextromethorphan and a SSRI to confirm dextromethorphan-induced serotonin syndrome. Our cases suggest supra-therapeutic dextromethorphan doses with a therapeutic amount of a SSRI are required for serotonin syndrome.

Interesting benefit
Mol Med Rep. 2015. Dextromethorphan provides neuroprotection via anti-inflammatory and anti-excitotoxicity effects in the cortex following traumatic brain injury.