July 12, 2012

Outcomes of Drug-Related Emergency Department Visits Associated with Polydrug Use

Polydrug use (use of more than one substance) can create complex chemical reactions in the body, with unpredictable outcomes.¹ Drugs that have a sedative effect can be especially dangerous when combined with other drugs or alcohol.² Use of multiple illicit or pharmaceutical drugs, including combinations with alcohol, may require immediate medical treatment followed by more advanced care and evaluation in a hospital setting. Characterizing the presence of multiple substances in drug-related emergency department (ED) visits can lead to a better understanding of which polydrug use behaviors most often require hospitalization. The Drug Abuse Warning Network (DAWN) can be used to generally describe ED visits involving multiple drugs; future reports will examine visits involving specific drug combinations in more detail.

DAWN is a public health surveillance system that monitors drug-related ED visits in the United States. To be a DAWN case, the ED visit must have involved a drug, either as the direct cause of the visit or as a contributing factor. This issue of The DAWN Report focuses on visits in 2009 that involved selected illicit drugs (cocaine, heroin, and marijuana) or nonmedical use³ of selected pharmaceuticals: narcotic pain relievers (e.g., OxyContin^®), benzodiazepines (e.g., Xanax^®), muscle relaxants (e.g., Flexeril^®), and central nervous system (CNS) stimulants (e.g., Ritalin^®). "Polydrug use" is defined in this report as the presence of more than one drug, including illicit drugs, pharmaceuticals, or alcohol. ED visits that result in admission to the same hospital are hereafter referred to as "hospitalizations"; patients may also be hospitalized after being transferred to another health care facility (e.g., psychiatric facility, veterans' hospital). Because drug-related ED visits often involve multiple drugs, some visits (and resulting hospitalizations) may be counted multiple times if they involve more than one of the drugs discussed in this report.

In 2009, about 4.5 million drug-related ED visits occurred; of these, cocaine was involved in 422,901 visits, marijuana was involved in 376,486 visits, and heroin was involved in 213,118 visits (Table 1). Among visits involving nonmedical use of pharmaceuticals, those involving narcotic pain relievers (342,983 visits) or benzodiazepines (312,931 visits) were most common, followed by muscle relaxants (50,878 visits) and CNS stimulants (21,799 visits).

For drug-related ED visits occurring in 2009, the likelihood of polydrug, also referred to as multiple drug, involvement varied depending on the type of drug involved. The majority of visits associated with use of cocaine or marijuana involved polydrug use (68 and 73 percent, respectively), whereas slightly more than half of heroin-related visits involved polydrug use (52 percent) (Figure 1). The majority of visits associated with the types of pharmaceuticals included in this report involved polydrug use (narcotic pain relievers: 63 percent, benzodiazepines: 79 percent, muscle relaxants: 80 percent, CNS stimulants: 67 percent).

Figure 1. Percentage of Emergency Department (ED) Visits Involving Multiple or Single Drugs for Selected Illicit Drugs and Pharmaceuticals: 2009

For ED visits that involved cocaine, the presence of other drugs did not appear to influence the outcome of the ED visit. About half of patients were treated and released for both single and polydrug cocaine use (51 and 53 percent, respectively) (Figure 2). Both groups were also equally likely to be admitted to the hospital (34 and 29 percent, respectively). However, patients whose ED visits involved polydrug cocaine use were slightly more likely than patients whose visits involved cocaine only to be transferred to another health care facility (12 vs. 8 percent).

Figure 2. Disposition of Emergency Department (ED) Visits Involving Cocaine: 2009

Polydrug use was associated with differing outcomes for ED visits involving marijuana or heroin. Patients whose ED visits involved polydrug marijuana use were more likely than those whose visits involved marijuana only to have been admitted to the hospital (23 vs. 16 percent) and less likely to have been treated and released (58 vs. 69 percent) (Figure 3). Similarly, patients whose ED visits involved polydrug heroin use were more likely than patients whose visits involved heroin only to have been admitted to the hospital (28 vs. 22 percent) and were less likely to have been treated and released (55 vs. 68 percent) (Figure 4).

Figure 3. Disposition of Emergency Department (ED) Visits Involving Marijuana: 2009

Figure 4. Disposition of Emergency Department (ED) Visits Involving Heroin: 2009

Among visits involving nonmedical use of narcotic pain relievers or benzodiazepines, polydrug use was associated with an increased likelihood of hospitalization. Patients whose visit involved nonmedical use of a narcotic pain reliever in combination with another drug were more likely than patients whose visit involved a narcotic pain reliever only to be admitted to the hospital (30 vs. 19 percent) and less likely to be treated and released (56 vs. 74 percent) (Figure 5). Patients whose ED visits involved nonmedical use of a benzodiazepine in combination with another drug were more likely than those whose visits involved nonmedical use of a benzodiazepine only to have been admitted to the hospital (32 vs. 26 percent) and were less likely to be treated and released (52 vs. 63 percent) (Figure 6).

Figure 5. Disposition of Emergency Department (ED) Visits Involving Nonmedical Use of Narcotic Pain Relievers: 2009

Figure 6. Disposition of Emergency Department (ED) Visits Involving Nonmedical Use of Benzodiazepines: 2009

ED visits involving nonmedical use of muscle relaxants had similar outcomes regardless of the presence of polydrug use (Figure 7). For visits involving nonmedical use of a CNS stimulant, those involving polydrug use were less likely than those involving a CNS stimulant alone to have been treated and released (65 vs. 78 percent); however, other outcomes were similar between the two groups (Figure 8).

Figure 7. Disposition of Emergency Department (ED) Visits Involving Nonmedical Use of Muscle Relaxants: 2009

Figure 8. Disposition of Emergency Department (ED) Visits Involving Nonmedical Use of Central Nervous System (CNS) Stimulants: 2009

Polydrug use can cause unsafe drug interactions, amplifying the effects of individual drugs. Although the effects will vary depending on the types of drugs involved, the dangers of combining multiple drugs may increase the need for medical treatment. This report presents general information on polydrug use; future reports will focus on more specific drug combinations and outcomes.

The presence of injuries, co-occurring medical and mental health conditions, and the patient's age can influence the likelihood of hospitalization following a drug-related ED visit. However, this report suggests that the association between polydrug visits and hospitalization varies based on the drugs that were involved in the visit. Cocaine is known to interact dangerously with other substances (e.g., alcohol)⁴; however, factors other than polydrug use may have influenced the outcome of cocaine-related visits. Polydrug use visits involving cocaine, muscle relaxant, or CNS stimulant combinations were not associated with an increased likelihood of hospitalization compared with visits involving those single drugs alone.

Among visits involving narcotic pain relievers or benzodiazepines, polydrug use was associated with an increased likelihood of hospitalization. These particular drugs cause sedation, which may be compounded by other drugs or alcohol.² The effects of such drug combinations may require efforts to resuscitate or treat suppressed breathing in the ED, with subsequent hospitalization for close monitoring.⁵ Visits involving marijuana or heroin combinations were also more likely to result in hospitalization compared with visits involving a single drug. These findings, coupled with the fact that half of substance abuse treatment admissions involve multiple substances,⁶ stress the importance of comprehensive treatment programs that address polydrug use. Medical costs for an ED patient inevitably increase when that patient requires hospitalization or specialized treatment in another health care facility. Therefore, reducing polydrug use may help decrease the overall amount of resources needed to treat drug-related health problems.

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