Dibutylone (bk-DMBDB) is a stimulant drug of the amphetamine, phenethylamine, and cathinone drug classes. It is structurally related to butylone, a designer drug that has been detected in products marketed as bath salts or plant food.
Dibutylone is a psychedelic research chemical, structurally related to methylone and acting as a reuptake inhibitor. You can see its reactions when you mix it with various other substances. Structurally similar to (Â±)-2-Methylamino-1-(3,4-methylenedioxyphenyl)propan-1-one, or Methylone, Dibutylone is a psychedelic research chemical introduced in the category of the amphetamine, phenethylamine and cathinone chemical classes.
The number of emerging novel stimulants modified based on beta-keto variations of amphetamine-like substances continues to rise. Dibutylone reports described in the medical and toxicological literature are limited, therefore little information is available in terms of quantitative confirmation or metabolism. During this study, authentic human specimens, including blood, urine, vitreous humor, oral fluid and liver were quantitatively and qualitatively analyzed for the presence of dibutylone and butylone, with paired case history and demographic information. Dibutylone concentrations were variable across all specimen types, specifically ranging from 10 to 1,400 ng/mL in postmortem blood specimens. The metabolic profile of dibutylone was mapped by in vitro incubation with human liver microsomes (HLM). Samples were analyzed using a SCIEX TripleTOF® 5600+ quadrupole time-of-flight mass spectrometer.
Data processing was conducted using MetabolitePilot™. Authentic human specimens, including blood, urine, vitreous humor, oral fluid and liver, were utilized for in vivo verification of five HLM-generated metabolites in analytically confirmed cases of dibutylone use. Butylone was confirmed as a metabolite of dibutylone, but issues involving co-ingestion of these two novel stimulants or potential co-existence from synthesis lead to ineffectiveness as a true biomarker. Hydrogenation of the beta-ketone of dibutylone resulted in the most prominent metabolite found in human specimens, and its uniqueness to dibutylone over other stimulants leads to its classification as an appropriate biomarker for dibutylone ingestion. This is the first study to map the metabolic profile of dibutylone, including verification in authentic specimens, confirming metabolic conversion to butylone and identifying biomarkers more useful in forensic toxicological drug testing.
As with other classifications of novel psychoactive substances (NPS), novel stimulant and novel psychedelic identification and proliferation have been well characterized and monitored throughout recent years (1–3). Families of novel stimulant drugs based on the cathinone (beta-keto amphetamine) structure, some with hallucinogenic or mood heightening empathogenic, entactogenic or euphoric effects, were among the first waves of NPS identified in Europe in the 2000s (4, 5).
While these classes of compounds were originally reported to have less intense effects than traditional stimulant/psychedelic drugs, such as 3,4-methylenedioxymethamphetamine (MDMA) (6), reports of adverse events continue to appear (7), and potency information for these novel compounds is often lacking in human subjects or unavailable (7). Nonetheless, novel stimulant and psychedelic drugs continue to be identified in toxicological casework on a regular basis, and the most prevalent analyte in these classes changes from year to year (8).
Novel stimulants are referred to by structural classifications, including amphetamine, phenethylamine and cathinone sub-classes (9), however the terminology has significant overlap. There are additional sub-classifications to those previously mentioned, but one of the most popular is the substituted beta-keto-methylenedioxyamphetamines, whose popular names end in “-lone” and include methylone, dimethylone, ethylone, butylone, pentylone and others (Figure 1).
This beta-keto sub-class dates back to the synthesis of methylone in the 1950s (10) and patents filed in the 1960s (11) including dibutylone, pentylone, eutylone and N-ethyl pentylone (ephylone). Many years later in the mid-1990s, methylone (bk-MDMA) was nicknamed by Peyton Jacob III and Alexander Shulgin (12). Over half a century after its synthesis, methylone was identified in the street drug supply being substituted and/or sold for recreational purposes to circumvent illegality of MDMA and other traditional stimulants (5), leading to the proliferation of methylone and its analogs in recent years, up to and including seizures of dibutylone in the United States in 2016 (13, 14).
Following the appearance of methylone, a succession of novel stimulants was seen including butylone beginning in 2012 (15, 16), ethylone in 2014 (17, 18) and dibutylone in 2016 (13, 14). Dibutylone (Figure 1), known as beta-keto-dimethylbenzodioxolylbutanamine, bk-DMBDB, bk-MMBDB or methylbutylone, is one of the more recent novel stimulants in this series to be reported in forensic toxicology casework and the street drug supply. The first mention of dibutylone came in a 1967 patent, alongside other now emerging novel stimulants (11). Dibutylone was first reported to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) by Finland in 2010 (19), but more detailed information was not available until 2014 when tablets were seized and positively identified in Sweden (20). In the United States, dibutylone was not reported until 2016 (13), by which time it had become the fourth most commonly detected phenethylamine drug in the country and most commonly detected novel phenethylamine, overtaking ethylone from 2015, according to data generated by the National Forensic Laboratory Identification System (NFLIS). As of 2016, dibutylone was still reported as the most commonly detected novel phenethylamine (14).
Currently, there are limited reports in the literature involving intoxications or deaths with these beta-keto-methylenedioxyamphetamines, as many laboratories do not routinely test for them, and their specific toxicity profile is unknown (7). Pharmacological and toxicological effects of dibutylone have not been previously reported, although it has been proposed that its effects and adverse events would be similar to previously described novel stimulants (21). One possible comparison is to butylone toxicity (15). In this case described as serotonin syndrome, resulting from the ingestion of an “Ecstasy” pill containing butylone and methylone, hospital personnel reported tachycardia, tachypnea, and hypertension and the patient experienced diaphoresis, tremors and hyperreflexia. The patient was aggressively cooled, but due to multi-system organ failure eventually died. In another case of attempted suicide following ingestion of 10 butylone tablets, hospital personnel report tachycardia, hypertension, increased muscle tonus, hypersalivation, mydriasis and hyperthermia, in addition to noted arrhythmias (22). Butylone is also reported to cause hyperventilation and prominent behavioral changes (23).
To better assist laboratories and toxicologists in the identification and interpretation of NPS use and drug positivity, it is important to understand novel stimulant metabolic fate as the identification of metabolites can prolong detection windows. Furthermore, due to the structural relationships between the members of the beta-keto methylenedioxyamphetamine drug class, many novel stimulants are metabolized into another biologically active novel stimulant (8, 24–26), which can create scenarios where multiple drugs are contributing to effects.
This manuscript reports analytical methods for the identification and quantitation of dibutylone and its in vitro metabolic products, and confirmation of these metabolites in authentic human biological specimens from dibutylone intoxications.
Dibutylone Chemicals and reagents
Butylone and dibutylone were purchased from Cayman Chemical (Ann Arbor, MI, USA). Reference material was prepared at 1 mg/mL in methanol. Diazepam (1 mg/mL) was purchased from Cerilliant (Round Rock, TX, USA). Nicotinamide adenine dinucleotide phosphate (NADPH) was purchased from Cayman and used as the cofactor during human liver microsome (HLM) incubations. Sodium phosphate was purchased from Sigma-Aldrich (St. Louis, MO, USA) to prepare a buffer solution at 100 mM (pH 7.4) with addition of magnesium chloride (Sigma-Aldrich) at 10 mM.
All solvents and reagents, of LCMS grade purity, used during sample preparation and instrumental analysis were purchased from Honeywell (Morris Plains, NJ, USA). Pooled HLMs (20 mg/mL, 50 donors) were purchased from ThermoFisher Scientific (Waltham, MA, USA) and stored at −80°C. Sodium borate decahydrate was purchased from EMD Millipore Corporation (Darmstadt, Germany) for preparation of Borax buffer.
Dibutylone confirmation and quantitation
NMS Labs (Willow Grove, PA, USA) provided discarded postmortem blood (n = 9), urine (n = 4), vitreous humor (n = 1) and liver (n = 1) specimens from death investigation toxicology casework (n = 9) that had previously tested positive for dibutylone. Specimens were collected between January 2016 and July 2017. Personal identifiers were removed from any specimens or case histories before being provided. Case circumstances, when available, were tabulated and are provided in Table I (Case 1–9). Specimens were extracted using solid phase extraction (Agilent Bond Elut Plexa PXC, 3 mL, 30 mg). The extraction cartridges were conditioned with acetonitrile and water, the sample was applied and washed with hydrochloric acid in water (0.1 N) and acetonitrile, and the sample was eluted using a mixture of water, acetonitrile and ammonium hydroxide (55:40:5, v-v:v).