The concern about the impact of active pharmaceutical compounds on the environment has been growing for decades. This work looks at pharmaceutical wastes as a source of valuable active compounds proposing the use of novel aqueous biphasic systems (ABS) composed of quaternary ammonium compounds and different salts to the extraction of active substances from pharmaceutical wastes. The phase diagrams of ABS of six quaternary ammonium halides ([N-2,N-2,N-2,N-2]Br, [N-2,N-2,N-2,N-2]Cl, [N-3,N-3,N-3,N-3]Cl, [N-4,N-4,N-4,N-4]Br and [N-4,N-4,N-4,N-4]Cl) and three different salts (potassium citrate buffer, potassium carbonate and potassium phosphate buffer) were established at 298 (+/- 1) K. These systems allow the investigation of the influence of the ammonium structure, the salting-out agent, and the pH of the aqueous medium. They were then applied to the extraction of paracetamol that displays an extensive partition towards the ammonium-rich phase. All the studied systems, employing both the model compound and real matrix reveal a great aptitude to recover paracetamol from pharmaceutical wastes, presenting extraction efficiencies ranging from around 80% up to 100%. (c) 2013 Elsevier B.V. All rights reserved.