The Misuse of Drugs Act (MDA) No. 5 of 1973 is the main piece of drug legislation in the country. It contains the list of controlled substances which are divided into three Schedules. Several new psychoactive substances have been added to the list of controlled substances. For instance, on 15 November 2010 mephedrone, BZP and TFMPP were added to the First Schedule of the Misuse of Drugs Act. In May 2014, all NPS listed in the Fifth Schedule (temporary banned) were reclassified as Class A drugs and subsequently listed in the First Schedule of the MDA, under which the trafficking, manufacture, import, export, possession or consumption of these substances will constitute an offence under the MDA (Annex A for NPS classified as Class A drugs). In April 2015, the Central Narcotics Bureau (CNB) announced that with effect on 1 May 2015, 14 NPS that were in the Fifth Schedule of the Misuse of Drugs Act (MDA) (i.e. temporarily banned) were going to be listed in the First Schedule of the same Act. This means that these substances (5-Fluoro-APINACA or 5F-AKB48 and its fluoro positional isomers in the pentyl group; 5-Fluoro-APICA or STS-135 and its fluoro positional isomers in the pentyl group; AB-FUBINACA and its fluoro positional isomers in the phenyl ring; 4-APB; 7-APB; 4-APDB; 7-APDB; 25B-NBOMe; 25C-NBOMe; 25H-NBOMe; 25I-NBOMe; BB-22 or QUCHIC; 5-Fluoro-PB-22 or 5-Fluoro-QUPIC and its fluoro positional isomers in the pentyl group and PB-22 or QUPIC.) were reclassified as Class A controlled drugs. In addition, the NPS AH-7921  and its dichloro positional isomers in the phenyl ring were also listed in the First Schedule as a Class A controlled drug.

With effect from 1 May 2017, the Central Narcotics Bureau (CNB) of Singapore has incorporated five NPS, including the synthetic opioid U-47700 and four synthetic cannabinoids (5F-MN-24, MDMB-CHMICA, NM-2201 and THJ-018) to the national list of Class A controlled drugs of the Misuse of Drugs Act (MDA). Nine additional NPS were added to the Fifth Schedule of the MDA, which places them under temporary control in Singapore. U-47700 was already placed under international control (Schedule I of the Single Convention on Narcotics Drugs 1961) earlier this year by a decision of the Commission on Narcotic Drugs.