A number of synthetic derivatives of cocaine have been investigated as potential pharmaceutical agents (e.g. 4-fluorococaine and 2-hydroxycocaine), but only two have been reported as potential substances of misuse, namely 3-(p-fluorobenzoyloxy)tropane, pFBT and dimethocaine. Both are available as ‘research chemicals’ from retail websites or have been identified in ‘legal highs’ products.
The structure of pFBT is closely related to that of cocaine, however dimethocaine lacks a tropane ring and more closely resembles the structure of procaine, a local anaesthetic drug without psychoactive properties. There is therefore some doubt as to whether dimethocaine itself has psychoactive effects in humans. Neither substance is under international control, and apart from Denmark (pFBT) and Romania (dimethocaine) there are no national controls in the EU.
Molecular structure: cocaine
Molecular formula: C17H21NO4
Molecular weight: 303.35 g/mol
Molecular structure: 3-(p-fluorobenzoyloxy)tropane (pFBT)
Molecular formula: C15H18NO2
Molecular weight: 263.31 g/mol
Molecular structure: dimethocaine
Molecular formula: C16H26N2O2
Molecular weight: 278.39 g/mol
Molecular structure: procaine
Molecular formula: C13H20N2O2
Molecular weight: 236.31 g/mol
Like cocaine and some other local anaesthetics, these substances are benzoic acid esters. The structure of 3-(p-fluorobenzoyloxy)tropane (pFBT) is closely related to that of cocaine, but it has a fluorine atom in the phenyl ring, and lacks a carboxyl group on the tropane ring. The formal name for 3-(p-fluorobenzyloxy)-tropane is (1R,5S)-(8-methyl-8-azabicyclo[3.2.1]octan-3-yl)-4-fluorobenzoate (CAS: 172883-97-5), but it is also known as 4-fluorotropacocaine, 3-pseudotropyl-4-fluorobenzoate or simply pFBT. It can be synthesised by the condensation of tropine with p-fluorobenzoic acid, where tropine is obtained from the hydrolysis of atropine.
Dimethocaine lacks a tropane ring and more closely resembles the structure of procaine, a local anaesthetic drug without psychoactive properties. Dimethocaine is formally named as (3-diethylamino-2,2-dimethylpropyl)-4-aminobenzoate (CAS: 94-15-5), but is also known as larocaine or simply DMC. By analogy with the manufacture of procaine, a possible route of synthesis would be to condense 4-aminobenzoic acid ethyl ester with diethylamino-t-butanol.
Both pFBT and dimethocaine are found as white powders. It is not clear if they are in the form of free bases or as salts.
Little is known about the detailed pharmacokinetics and pharamacodynamics of these substances in humans. Apart from any central nervous system activity, both act as local anaesthetics. User accounts on the Internet describe pFBT as being a stimulant. As with cocaine, pFBT is anecdotally reported to cause hypertension, tachycardia, anxiety and temporary psychosis.
In animals, dimethocaine produces stimulant effects and inhibits dopamine uptake almost as effectively as cocaine. However, there is some doubt as to whether it is psychoactive in humans. User accounts on the Internet note that it produces a mild stimulant effect.
Both pFBT and dimethocaine are synthetic substances available as ‘research chemicals’ from Internet suppliers or in certain ‘legal highs’ products from ‘head shops’.
Like cocaine, both substances would have to be insufflated (snorted) since following ingestion they would be hydrolysed by esterases in the digestive system.
There do not appear to be any specific street or user names for pFBT. In Ireland, dimethocaine has been sold in ‘head shops’ in products such as Mind Melt, Amplified and Mint Mania.
Both substances can be analysed by gas chromatography-mass spectrometry (GCMS). For pFBT, the principal ions in the electron-impact (EI) mass spectrum are m/z (% abundance): 82(54.7), 95(54.1), 124(100.0), 140(6.0), 263(13.7). The principal ions in the EI mass spectrum of dimethocaine are m/z (% abundance): 86(100.0), 120(18.9), 137(2.5), 278(0.7).
Neither substance is under international control, and apart from Denmark (pFBT) and Romania (dimethocaine) there are no national controls in the EU Member States.
An EMCDDA ‘snapshot’ performed in January and February 2011 found that dimethocaine was offered in more than 20 online shops with prices ranging between EUR 20 and 30 for one gram. It is normally sold as a 'research chemical’, ‘legal high’ or ‘plant food’.
Neither substance has any clinical use in the EU.
Rigon, A.R., Takahashi, R.N. (1966), 'Stimulant activities of dimethocaine in mice: reinforcing and anxiogenic effects', Psychopharmacology (Berlin) 127(4), pp. 323–7.
Singh, S. (2000), 'Chemistry, Design, and Structure-Activity Relationship of Cocaine Antagonists', Chemical Reviews, 100, pp. 925–1024.
Wilcox, K. M., Rowlett, J.K., Paul, I.A., Ordway, G.A., Woolverton, W.L. (2000), 'On the relationship between the dopamine transporter and the reinforcing effects of local anesthetics in rhesus monkeys: practical and theoretical concerns', Psychopharmacology, 153, pp. 139–147.
Wilcox, K.M., Kimmel, H.L., Lindsey, K.P., Votaw, J.R., Goodman, M.M. and Howell, L.L. (2005), 'In vivo comparison of the reinforcing and dopamine transporter effects of local anesthetics in rhesus monkeys', Synapse 58(4), pp. 220–28.
Wohlfarth , A. and Weinmann, W. (2010), 'Bioanalysis of new designer drugs', Bioanalysis, 2(5), pp. 965–79.
Woodward, J.J., Compton, D.M., Balster, R.L,, Martin, B.R. (1995), 'In vitro and in vivo effects of cocaine and selected local anesthetics on the dopamine transporter', European Journal of Pharmacology, 277(1), pp. 7–13.