A 65 year old lady was sent to Accident and Emergency Dept for impaired consciousness. She was well three hours prior to hospital admission. She had a past psychiatric history of depression and attempted suicide. Empty medication bottles and a suicidal note were found at home. Acute drug overdose was suspected. On physical examination, her Glasgow Coma Scale was E1M5V2, blood pressure was 80/40 mmHg, heart rate was 150 beats perminute, and pupil size was 4 mm. Involuntary jerking muscle contractions (myoclonus) were noted in inspection. The electrocardiogram (ECG) showed a widening of QRS of duration 183 milliseconds.

a)Which class of therapeutic drug overdose could explain her clinical presentations? Name ONE example of the drug. Name TWO other therapeutic indications apart from depression (3 marks)

b) Describe the mechanisms of the drug toxicities:

i) Widen QRS complex in the ECG (1 mark)

ii) Tachycardia (2 marks)

iii) Hypotension (1 mark)

iv) Impaired consciousness and confusion (1 mark)

c) Name TWO other medications that could cause prolonged QRS complex in ECG when in overdose settings (2 marks)

d) Name ONE serious CNS toxicity of this medication poisoning (1 mark)

e) List the therapeutic agent useful for treatment of the drug toxicities:

i) conduction disturbances and arrhythmias (1 mark)

ii) hypotension (1 mark)

iii) seizures (1 mark)

f) The patient recovered from treatment and the psychiatrist decided to switch her treatment to a selective serotonin reuptake inhibitor (SSRI)

i) Name ONE example of SSRI

ii) Describe the mechanism of actions of this medication (1 mark)

iii) What serious electrolyte disturbance may occur with this medication (1 mark)

iv) What potential serious drug interaction can occur with this medication and describe the cause of this interaction? (2 marks)

v) Name ONE herb that can cause this serious interaction with this medication (mark)