5-CL-ADB-A

5-CL-ADB-A is a potentially misleading name used in some drug-market and monitoring contexts for MDMB-4en-PINACA, also known as MDMB-PENINACA. The name does not reliably describe a chlorine-substituted compound. The European risk assessment notes that “5Cl-ADB-A” has been used synonymously for MDMB-4en-PINACA, while warning that the code is potentially confusing. MDMB-4en-PINACA is a potent indazole-based synthetic cannabinoid receptor agonist associated with severe intoxications and deaths.

Chemistry and nomenclature

MDMB-4en-PINACA is methyl 3,3-dimethyl-2-{[1-(pent-4-en-1-yl)-1H-indazole-3-carbonyl]amino}butanoate. It contains an indazole core, an N-pent-4-enyl substituent and a methyl tert-leucinate carboxamide group. It is chemically distinct from 5-chloro-ADB or 5F-ADB.

The EUDA risk assessment specifically notes that the “5Cl-ADB-A” code appears to be used synonymously for MDMB-4en-PINACA by some online retailers, although the meaning of the suffix is unclear. Forensic identification should therefore rely on the full structure and analytical confirmation rather than the shorthand alone (EUDA risk assessment of MDMB-4en-PINACA, 2021).

Pharmacology

The (S)-enantiomer of MDMB-4en-PINACA is a potent full agonist at the CB₁ receptor in vitro. This mechanism is consistent with the strong central effects reported for synthetic cannabinoid receptor agonists. Its activity is not equivalent to that of THC, which is a partial agonist at CB₁ under many experimental conditions.

Reported effects

Human reports and clinical records describe severe central nervous system effects, including confusion, agitation, delirium, impaired mental status and seizures. Synthetic cannabinoid intoxication may also involve reduced consciousness and marked behavioural disturbance. These clinical findings are more informative than anecdotal comparisons with cannabis.

Clinical and forensic findings

The EUDA risk assessment recorded eleven acute intoxications with confirmed exposure reported by the United Kingdom between January and August 2020. Ten cases were considered life-threatening and required hospitalisation. Twelve deaths with confirmed exposure were reported by Hungary, the United Kingdom and Sweden between January 2019 and August 2020; other substances were detected in all cases, and MDMB-4en-PINACA was considered the cause or a contributor in some of them (EUDA risk assessment, 2021).

Toxicity and research limitations

The EUDA concluded that MDMB-4en-PINACA posed a serious health concern because of its potency, variable content in products and confirmed severe intoxications. Chronic human effects, dependence liability and long-term outcomes were less well documented. The available clinical record also includes polydrug cases, which complicates attribution of individual symptoms and deaths.

The name 5-CL-ADB-A should not be interpreted as proof that a chlorine atom is present. When the exact chemical identity is uncertain, clinical or forensic findings should be attributed to MDMB-4en-PINACA only when the analytical evidence supports that identification.

Related compounds

MDMB-4en-PINACA is related to 5F-ADB, 5F-MDMB-2201 and other indazole-carboxamide synthetic cannabinoids. Its pent-4-enyl side chain distinguishes it from the fluorinated alkyl analogues.