According to Mr Baker's report, Mr A made the error because he took medication assigned to the person staying in Mr B's old room.
It is understood Mr B had moved rooms before Mr A's shift began on March 4.
When Mr A returned Mr B's blister pack to the medication filing draw, he realised his error, immediately alerted fellow staff members and an ambulance was called.
While on his way to hospital, Mr B - who began to feel dizzy after taking the medication - comatosed and had trouble breathing, the report said.
He was intubated and put on a ventilator when he arrived, before being admitted to the intensive care unit.
As there was no way to remove clozapine from a person's bloodstream, supportive care was provided to Mr B.
"His coma gradually resolved and he had no cardiac complications," the report said.
Mr B was taken off the breathing apparatus after seven hours.
Following the incident, a formal apology was made to Mr B and his family by the health service.
Mr A also attended a second medication safety session, and all staff at the service were "refamiliarised" with the protocols around medication administration.
"I have looked upon this incident with a deep sense of regret [and] I acknowledge my actions as negligent," Mr A said.
The residential service also changed its medication storage system to be based solely on a patient's identity number, rather than room number.