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Competing Interests: No conflicts of interest were reported.

Competing Interests: No conflicts of interest were reported.

Recent reports suggest that acute intoxications by synthetic cannabinoids are increasing in the United States (1,2). Synthetic cannabinoids, which were research compounds in the 1980s, are now produced overseas; the first shipment recognized to contain synthetic cannabinoids was seized at a U.S. border in 2008 (3). Fifteen synthetic cannabinoids are Schedule I controlled substances (3), but enforcement is hampered by the continual introduction of new chemical compounds (1,3). Studies of synthetic cannabinoids indicate higher cannabinoid receptor binding affinities, effects two to 100 times more potent than Δ(9)-tetrahydrocannabinol (the principal psychoactive constituent of cannabis), noncannabinoid receptor binding, and genotoxicity (4,5). Acute synthetic cannabinoid exposure reportedly causes a range of mild to severe neuropsychiatric, cardiovascular, renal, and other effects (4,6,7); chronic use might lead to psychosis (6,8). During 2010-2015, physicians in the Toxicology Investigators Consortium (ToxIC) treated 456 patients for synthetic cannabinoid intoxications; 277 of the 456 patients reported synthetic cannabinoids as the sole toxicologic agent. Among these 277 patients, the most common clinical signs of intoxication were neurologic (agitation, central nervous system depression/coma, and delirium/toxic psychosis). Relative to all cases logged by 50 different sites in the ToxIC Case Registry, there was a statistically significant association between reporting year and the annual proportion of synthetic cannabinoid cases. In 2015, reported cases of synthetic cannabinoid intoxication increased at several ToxIC sites, corroborating reported upward trends in the numbers of such cases (1,2) and underscoring the need for prevention.

On April 2, 2015, four patients were evaluated at the University of Mississippi Medical Center (UMMC) in Jackson, Mississippi, for agitated delirium after using synthetic cannabinoids. Over the next 3 days, 24 additional persons went to UMMC with illnesses suspected to be related to synthetic cannabinoid use; one patient died. UMMC notified the Mississippi State Department of Health, which issued a statewide alert via the Health Alert Network on April 5, requesting that health care providers report suspected cases of synthetic cannabinoid intoxication to the Mississippi Poison Control Center (MPCC). A suspected case was defined as the occurrence of at least two of the following symptoms: sweating, severe agitation, or psychosis in a person with known or suspected synthetic cannabinoid use. A second statewide alert was issued on April 13, instructing all Mississippi emergency departments to submit line lists of suspected patients to MPCC each day. By April 21, 16 days after the first alert was issued, MPCC had received reports of approximately 400 cases, including eight deaths possibly linked to synthetic cannabinoid use; in contrast, during April 2012–March 2015, the median number of telephone calls to MPCC regarding synthetic cannabinoid use was one per month (range = 0–11). The Mississippi State Department of Health, with the assistance of CDC, initiated an investigation to better characterize the outbreak, identify risk factors associated with severe illness, and prevent additional illnesses and deaths.

On April 6, 2015, CDC received notification of an increase in telephone calls to U.S. poison centers related to synthetic cannabinoid use. Monthly calls to all poison centers are tracked by the National Poison Data System, which reported that adverse health effects or concerns about possible adverse health effects related to synthetic cannabinoid use increased 330% from 349 in January 2015 to 1,501 in April 2015. Synthetic cannabinoids include various psychoactive chemicals or a mixture of such chemicals that are sprayed onto plant material, which is then often smoked or ingested to achieve a "high." These products are sold under a variety of names (e.g., synthetic marijuana, spice, K2, black mamba, and crazy clown) and can be sold in retail outlets as herbal products. Law enforcement agencies have regulated a number of these substances; however, manufacturers of synthetic cannabinoids frequently change the formulation to avoid detection and regulation. After the initial notification, CDC analyzed information from the National Poison Data System on reported adverse health effects related to synthetic cannabinoid use for the period January-May 2015.

On August 30, 2013, the Colorado Department of Public Health and Environment (CDPHE) was notified by several hospitals of an increase in the number of patients visiting their emergency departments (EDs) with altered mental status after using synthetic marijuana. Synthetic marijuana is dried plant material sprayed with various synthetic cannabinoids and smoked as an alternative to smoking marijuana. In response to the increase in ED visits associated with the use of synthetic marijuana, CDPHE asked all Colorado EDs to report through EMResource (a web-based reporting system) any patients examined on or after August 21 with altered mental status after use of a synthetic marijuana product. Serum and urine specimens from patients also were requested. On September 8, CDPHE, with the assistance of CDC, began an epidemiologic investigation to characterize the outbreak, determine the active substance and source of the synthetic marijuana product, and prevent further morbidity and mortality. Investigators reviewed ED visit reports submitted through EMResource and medical charts. A probable case was defined as any illness resulting in a visit to a Colorado ED during August 21-September 18, 2013, by a patient with suspected synthetic marijuana use in the 24 hours preceding illness onset. Of 263 patient visits reported to CDPHE through EMResource (214) and other means, such as e-mail and fax (49), a total of 221 (84%) represented probable cases (Figure).

On August 23, 2013, the Georgia Poison Center was notified of eight persons examined in an emergency department in Brunswick, Georgia, after smoking or inhaling fumes from synthetic cannabinoids. The Georgia Poison Center notified the Georgia Drug and Narcotics Agency, which informed the Georgia Department of Public Health (DPH). The Brunswick emergency department was asked to report any additional patients who reported use of synthetic cannabinoid to the Coastal District Health Department. DPH investigators reviewed recent medical records of patients who had gone to the emergency department and found that 22 patients had been examined after using synthetic cannabinoids during August 22-September 9, 2013.

In March 2012, the Wyoming Department of Health was notified by Natrona County public health officials regarding three patients hospitalized for unexplained acute kidney injury (AKI), all of whom reported recent use of synthetic cannabinoids (SCs), sometimes referred to as "synthetic marijuana." SCs are designer drugs of abuse typically dissolved in a solvent, applied to dried plant material, and smoked as an alternative to marijuana. AKI has not been reported previously in users of SCs and might be associated with 1) a previously unrecognized toxicity, 2) a contaminant or a known nephrotoxin present in a single batch of drug, or 3) a new SC compound entering the market. After the Wyoming Department of Health launched an investigation and issued an alert, a total of 16 cases of AKI after SC use were reported in six states. Review of medical records, follow-up interviews with several patients, and laboratory analysis of product samples and clinical specimens were performed. The results of the investigation determined that no single SC brand or compound explained all 16 cases. Toxicologic analysis of product samples and clinical specimens (available from seven cases) identified a fluorinated SC previously unreported in synthetic marijuana products: (1-(5-fluoropentyl)-1H-indol-3-yl)(2,2,3,3-tetramethylcyclopropyl) methanone, also known as XLR-11, in four of five product samples and four of six patients' clinical specimens. Public health practitioners, poison center staff members, and clinicians should be aware of the potential for renal or other unusual toxicities in users of SC products and should ask about SC use in cases of unexplained AKI.