Clozapine

Clozapine (中文:[[ ]])is an atypical antipsychotic or 2nd Generation antipsychotic medication. It is specifically used to treat treatment resistant schizophrenia (TRS), which affects approximately 1 in 3 people with the condition. These people include those who:

• Have tried at least 2 other antipsychotic medications that did not work
• Are unable to tolerae other antipsychotics because of their side-effects

It may also be used to treat psychoses secondary to Parkinson’s disease.

Drug Names

Generic Name 藥名	HA Code 藥物代碼	Classification藥物分類
Clozapine Tab 25 mg	CLOZ01	P1S1S3
Clozapine Tab 100 mg	CLOZ02	P1S1S3

Mechanism of Action

Clozapine has only weak dopamine-receptor-blocking activity at D1, D2, D3 and D5 receptors, but shows high potency for the D4 receptor. It is also an antagonist at the serotonin 5-HT2A receptors, improving depression, anxiety and the negative cognitive symptoms associated with schizophrenia.

Dosage

Indication	Dose
Schizophrenia	By mouth ADULT: ADULT (18 – 59 YEARS): 12.5 mg 1- 2 times daily on day 1, 25 – 50 mg on day 2 Then increased by 25 – 50 mg daily over 14 – 21 days up to 300 mg daily in divided doses Usual dose 200 – 450 mg daily Maximum 900 mg daily ADULT (≧ 60 years) 12.5 ng daily on day 1 25 – 37.5 mg on day 2, Then increased by 25 mg daily over 14 – 21 days up to 300 mg daily in divided doses, Usual dose 200 – 450 mg daily Maximum 900 mg daily
Psychosis in Parkinson’s disease	By mouth ADULT: 15 mg once daily Maximum 30 mg once daily
Adjunct treatment of major depressive disorder	By mouth ADULT: 12.5 mg at bedtime Increased by 12.5 mg up to twice weekly Usual dose range 25 – 37.5 mg at bedtime Maximum 100 mg daily in 1 – 2 divided doses

DOSE ADJUSTMENTS DUE TO INTERACTIONS Dose adjustment may be necessary if smoking started or stopped during treatment.

How long will it take before clozapine begins to work? Some people feel the benefit of clozapine within a few days, others may need a few months or even a year.

• 1 in 3 people with TRS have an improvement within 6 weeks
• 2 in 3 people with TRS have an improvement after one year of treatment.