James St John-Smythe, also known as William Housen to many, died at the DGH on June 1 last year, an inquest heard.
The inquest at Eastbourne Town Hall on Thursday (April 1), was told Mr St John-Smythe, who lived in Southfields Road, had taken heroin and cocaine on May 26.
Dr Rose Moore-Moffatt told the inquest Mr St John-Symthe had paranoid schizophrenia and also suffered from depression and anxiety.
The inquest heard Clint Harvey was with Mr St John-Symthe on May 26. The pair had met up to take drugs in Junction Road.
Mr Harvey said they did this regularly and Mr St John-Smythe was used to injecting the drugs himself. After taking the drugs, Mr St James-Smythe collapsed and had a cardiac arrest.
The inquest heard emergency services were alerted to the incident just before 3pm. Ambulance crews and police attended the scene.
Tracey Phipps, an attending paramedic, said Mr St John-Smythe was unconscious and wasn’t breathing when she arrived.
At 3.30pm there was evidence of respiratory efforts from Mr St John-Smythe so he was taken to the DGH, arriving at 4pm.
In the days that followed he was treated on the intensive care unit but on June 1 at 3.30pm life support was turned off due to the brain injury he had suffered as a result of the cardiac arrest.
East Sussex coroner Alan Craze ruled that Mr St John-Smythe died from drug use which resulted in a cardiac arrest and hypoxic brain injury.