Mystery surrounds the death of a mentally ill Tolworth Hospital patient found with fatal levels of an anti-depressant in his body.

Retired postal worker Dudley McKenzie had four times the safe level of toxicity of bipolar medicine Venlafaxine, a postmortem examination found. No explanation could be found as to why the concentration was inconsistent with the prescribed dose, West London Coroner’s Court heard on July 12. Coroner Alison Thompson was unable to establish what drugs Mr McKenzie had taken in the two days prior to his death because the chart monitoring his intake had not been completed.

Mr McKenzie, 71, who was also taking medication for renal impairment and high blood pressure, died at the hospital on the night of February 16 last year. Nurse Susan Ngedbai Saffa, who gave Mr McKenzie medication shortly before his death, raised the alarm when he began to complain of stomach pains and started vomiting blood. Professor Athol Johnson, pharmacologist at the London Medical School, said it was likely Mr McKenzie died from taking too much of the drug over a period of time, rather than a one-off overdose. He said it was doubtful that someone in Mr McKenzie’s condition, described as thin and frail, could have got hold of the medication as it was locked away.

Mr McKenzie was admitted to Kingston Hospital for 10 days shortly before his death after collapsing on the ward.
According to reports he continued to take the prescribed dose, though his drug intake charts were not presented in court. Dr Deborah Stinson, who became senior psychiatrist at Tolworth Hospital after Mr McKenzie’s death, said she was shocked by the toxicology reports. Coroner Alison Thompson said it appeared he was treated well but did not rule out human error.

A spokeswoman for South West London and St George’s Mental Health Trust said it had carried out an investigation into Mr McKenzie’s death. She said speculating on why the doses of Venlafaxine prescribed to Mr McKenzie were inconsistent with what was found at postmortem examination was clinically irresponsible.