New drug link in race scandal Said he was not aware if More Joyous received an injection: John Singleton. Racing stewards are investigating whether More Joyous, the horse at the centre of the row between John Singleton and Gai Waterhouse, was injected with an anti-arthritic drug five days before racing poorly at Randwick at the weekend. Fairfax Media has been told the champion mare did not eat all her feed on Monday night after the injection of the drug pentosan polysulfate, raising concerns about her welfare. Never looked anything wrong with her work at any stage. Singleton said he was not aware if the horse had received an injection or had failed to eat its feed. I wouldn't know. I don't know about that," he said on Wednesday night. What is known is that More Joyous was given antibiotics last Thursday after suffering soreness in her neck. Sources in the racing industry told Fairfax Media that such a neck issue would be in keeping with an adverse reaction to an injection of pentosan, usually administered in the neck. Chief steward Ray Murrihy said he was investigating what medications the mare had been given. ""I am aware of the rumour that there was another therapeutic drug involved,"" he said. Gai Waterhouse is believed to have told stewards a spider bite may have caused the heat in the mare's neck. The Waterhouse foreman who looks after More Joyous, David Meijer, is set to be a key witness at Monday's stewards" inquiry into the embroglio, which erupted before Saturday's All Aged stakes. It was his responsibility to monitor what the horse ate and drank - a key indicator of the health and wellbeing in training. Despite leaving some feed, More Joyous was fit enough to be exercised on Tuesday at Randwick. She worked over 1200 metres in one minute 24 seconds. On Thursday she covered the same distance in one minute 19 seconds. Trackwork watcher Craig Thompson said he did not believe the horse had ""missed a beat"" from what he had seen of her on the track. ""More Joyous galloped on the Saturday after her previous start, then four times after that on each Tuesday and Thursday. Never looked anything wrong with her work at any stage, she never missed a beat."" Pentosan polysulfate is commonly used in racing to relieve pain and inflammation in horses" joints. It is not a prohibited substance, meaning that horses can be treated with it while racing. Gai Waterhouse declined to speak to to Fairfax Media on Wednesday. Racing NSW chief executive Peter V'landys and stewards will meet on Thursday to decide whether to allow this Monday's inquiry to be televised live, given the unprecedented public interest in the racing row.