Auranofin drug molecule. Auranofin, marketed under the name Ridaura, is a gold(i) complex classified by the World Health Organisation as an antirheumatic agent. It is used to treat rheumatoid arthritis but also has interesting antiparasitic and antiviral effects. Chemical formula is C20H34AuO9PS. Atoms are represented as spheres: carbon (grey), hydrogen (white), oxygen (red), phosphorus (orange), gold (yellow) and sulphur (green). Illustration.