London - Drugs similar to those used by serial rapist Reynhard Sinaga to knock out his victims are advertised online for just £11 (about R200), a Daily Mail investigation found.
Several websites offer GBL for sale in the form of industrial solvents, stain removers, rust removers and paint strippers.
But in the body, GBL – gamma butyrolactone – rapidly turns into the "date-rape drug" GHB.
It has a similar mood-altering effect to ecstasy and has been nicknamed "coma in a bottle" due to its potency.
A teaspoonful can cause unconsciousness or death.
European sellers online clearly state that GBL should be used for stain removal and cleaning only and not for human consumption – but there are no checks when making an order.
One product was offered for sale at £11 for 30ml, plus £6.50 delivery. The seller, based in Croatia, said it could be used to remove varnish, paint, graffiti and for cleaning wheel rims.
A product described as a paint, glue and synthetic resin remover, being sold from the Netherlands at £10 for 100ml, plus £18 shipping fees, listed the contents as 99 percent GBL, one percent cellulose.
Some sites will take payment only with cryptocurrencies. One sells "pure GBL" from £47 per 500ml but insists on "anonymous orders via Bitcoin". The website states that the odourless and colourless fluid is shipped in "stealth packaging to ensure delivery".
On the frequently asked questions section of its website it claims everyone is allowed to buy and own GBL and that it becomes illegal only if resold as a medicine.
GHB has been a Class C drug since 2003. Although GBL is used legally in industry, it has also been a Class C drug since 2009.