Jonny is a 45-year-old male computer programmer. He was brought into the hospital emergency room by his wife who was concerned about her husband's abnormal behaviour and strange beliefs. Jonny threw a computer on the floor because he felt the internet was sending electrical brainwaves to him. Furthermore, Jonny told the attending doctor that he heard voices telling him that his colleagues were trying to poison his food. Consequently, he refused to go to work. Jonny was admitted to the psychiatric ward and prescribed haloperidol 1mg 

(a) What is Jonny's likely diagnosis? What other conditions can haloperidol be used for? 

(3 marks) 

Jonny's symptoms improved after the commencement of haloperidol. He was then discharged, and the dose of haloperidol was gradually increased to 4mg daily. A year later, Jonny returned for his psychiatric follow-up appointment. He had very occasional auditory hallucinations but was fully aware that these were the symptoms of psychosis. His family was happy with the progress and Jonny was doing well at work. However, on examination, Jonny clearly showed signs of gynaecomastia. The psychiatrist suspected that gynecomastia was associated with haloperidol. 

(b) What is gynecomastia? What is the potential pharmacological mechanism of haloperidol-induced gynecomastia? 

(8 marks) 

The psychiatrist has decided to switch Jonny's treatment from haloperidol to quetiapine. Gynecomastia gradually improved over the next 12 months, and he continued on quetiapine modified-release tablet 600 mg once daily without relapse of psychotic symptoms for the next 24 months. During the health check-up, Jonny reported gaining a lot of weight since last year. The results of the glucose tolerance test showed impaired glucose tolerance. Subsequently, his family physician referred Jonny for psychiatry review because of the potential association between impaired glucose tolerance and quetiapine. 

(c) What are the potential mechanisms of antipsychotic-induced impaired glucose tolerance or diabetes? 

(4 marks) 

(d) What are the potential treatment options available to Jonny? 

(5 marks)