Barry K. Logan, 1 Ph.D., D-ABFT Combined Dextromethorphan and Chlorpheniramine Intoxication in Impaired Drivers ABSTRACT: Dextromethorphan is a nonprescription antitussive which has been gaining in popularity as an abused drug, because of the halluci- nogenic, dissociative, and intoxicating effects it produces at high doses. This report describes a series of eight drivers arrested for driving under the influence of the combined effects of dextromethorphan and chlorpheniramine, and a further four drivers under the influence of dextromethorphan alone. In the combined dextromethorphan ⁄ chlorpheniramine cases, blood dextromethorphan concentrations ranged from 150 to 1220 ng ⁄ mL (n = 8; mean 676 ng ⁄ mL, median 670 ng ⁄ mL), and chlorpheniramine concentrations ranged from 70 to 270 ng ⁄ mL (n = 8; mean 200 ng ⁄ mL, median 180 ng ⁄ mL). The four cases without chlorpheniramine present had blood dextromethorphan concentrations between 190 and 1000 ng ⁄ mL (mean 570 ng ⁄ mL, median 545 ng ⁄ mL). Some drivers had therapeutic concentrations of other drugs present. Drivers generally displayed symptoms of central nervous system (CNS) depressant intoxication, and there was gross evidence of impairment in their driving, including weaving, leaving the lane of travel, failing to obey traffic signals, and involvement in collisions. Drug Recognition Expert opinions confirmed that the subjects were under the influence of a drug in the CNS-depressant category. KEYWORDS: forensic science, dextromethorphan, chlorpheniramine, Coricidin, driving impairment, toxicology Dextromethorphan is an over-the-counter cough suppressant ⁄ antitussive, present in numerous cough, cold, and flu formulations. It is frequently taken in combination with analgesics (acetaminophen and aspirin), decongestants (phenylephrine, pseudoephedrine), and antihistamines (chlorpheniramine, brompheniramine) and a mucolytic (guaifenesin) for the symptomatic treatment of coughs, colds, and flu. Dextromethorphan is also abused for the intoxicating, hallucinogenic, and dissociative effects it produces when taken in high doses (1,2). Emergency room admission data from the Drug Abuse Warning Network (DAWN) indicate that of c. 2 million drug-related emer- gency room visits in 2006, about half a million involved nonmedical use of pharmaceuticals, of which 12,584 (0.7%) involved dextro- methorphan (3). Dextromethorphan-related emergency room visits involved nonmedical use 43% of the time, and adverse reactions 33% of the time. Patients aged 12–20 accounted for 48% of visits due to nonmedical use of dextromethorphan (4). Recently, we reported a series of five deaths in teenagers resulting from dextromethorphan abuse (5). A report from Wisconsin has documented patterns of dextro- methorphan-positive cases in that state’s driving under the influence (DUI) population (6). Many of these drivers (25%) were positive for chlorpheniramine also. We report eight cases of intoxication in individuals ingesting the dextromethorphan and chlorpheniramine combination common in some over-the-counter cough and cold remedies such as Coricidin Cough and Cold, Robitussin, and Equate (Wal-Mart) brands, for recreational purposes. The cases include available information on the subject’s driving behavior, appearance, Drug Recognition Expert (DRE) evaluation, field sobri- ety tests, observed symptoms, and toxicology results. These are compared to four dextromethorphan cases in which chlorphe- niramine was not present. We also report the patterns of use and dosage admitted to by some of the subjects. Methods Drivers were contacted by police for the investigation of impaired driving in the course of regular traffic law enforcement. Subjects determined by the arresting officer to be under the influ- ence of alcohol and or drugs were typically screened for alcohol by a breath test, and in cases where the circumstances suggested drug use, or the subject’s apparent level of intoxication could not be accounted for by their breath alcohol concentration, a further evalu- ation was carried out (7). The evaluation included an assessment of pulse, blood pressure, muscle tone, and eye indicators, including horizontal and vertical nystagmus, convergence, hippus, and pupil size. It also included psychomotor tests for impairment including a walk and turn test, one leg stand, a Romberg balance test, and a finger-to-nose test. Drivers were either assessed through the admin- istration of standardized field sobriety tests (SFSTs) (horizontal gaze nystagmus [HGN], one leg stand, walk, and turn), or the full DRE protocol (7). Blood was collected subsequent to the arrest and assessment. Toxicological analysis was performed at the Washington State Tox- icology Laboratory, Seattle, WA. Blood samples were screened using Enzyme Multiplied Immunoassay Technique (EMIT Ò ) for cocaine metabolite, opiates, benzodiazepines, barbiturates, cannabi- noids, amphetamines, phencyclidine, propoxyphene, methadone, and tricyclic antidepressants. Blood was extracted for basic and weakly acidic drug fractions, using liquid–liquid, and liquid–solid extraction procedures described elsewhere (8). Extracts were analyzed by gas chromatography, with flame ionization, nitrogen phosphorus, and mass selective detection. Screening and confirma- tion thresholds generally met or exceeded those described in Farrell et al. (9). Results Table 1 lists all 12 cases reported here. Ten subjects were male and two female. The average age of the subjects was 26.4 (15–51). Seven cases (1,3–8) had admissions or recent medical histories of 1 NMS Labs, 3701 Welsh Rd, Willow Grove, PA 18901. Received 12 June 2008; and in revised form 17 Nov. 2008; accepted 22 Nov. 2008. J Forensic Sci, September 2009, Vol. 54, No. 5 doi: 10.1111/j.1556-4029.2009.01127.x Available online at: www.blackwell-synergy.com 1176 Ó 2009 American Academy of Forensic Sciences