CHAPTER 7: Esters, Ethers, Salts, Homologues, Stereoisomers and Isotopes

The generic control of esters derives from early international legislation. Together with ethers, these controls were carried over into United Kingdom (UK) law, albeit limited to certain drug groups. This inclusion was necessary since these derivatives are readily converted biochemically to the parent compound. At various times, the UK legislation has also introduced controls on certain homologues, but this has led to continuing difficulties with the accepted definition of ‘homologue’ which in some cases differs from that intended by those who drafted the original legislation. Unlike the international legislation, the UK Misuse of Drugs Act introduced controls on the stereoisomers of controlled drugs. Thus, the two enantiomers (R and S) of amphetamine, for example, are both controlled by the overarching entry ‘amphetamine’ whereas in the United Nations 1971 Convention, the R and S-enantiomers (levamfetamine and dexamfetamine) as well as the racemate (a 50 : 50 mixture of the R and S-stereoisomers) are listed separately in Schedule II of that Convention. In a criminal trial in Sweden in the late 1990s, the defendants were charged with the unlawful manufacture of amphetamine. Their ultimately unsuccessful defence was that they intended to produce deuterated amphetamine. Since that was not listed in the legislation, it was argued that it could not be a scheduled substance. It is now generally accepted that any isotopic variant of a controlled substance is also controlled.