Five facts about clozapine

 In Medications, Mental Health

1. Patients generally say it works and they want to stay on it

A survey found that more than 85% of patients said they felt better on clozapine than their previous treatment, and wanted to stay on it. 87% said the benefits outweighed the negatives.(2)

Pie Chart Showing How patients feel on clozapine compared with previous treatment


2. Stopping smoking causes plasma levels to rise but the magnitude of the effect is unpredictable

The mean rise was 71.9% but this consisted of 10 patients with an average rise of 57.4% and one with a rise of 261.1%.(5)

Bar graph showing clozapine plasma levels before and after smoking cessation


3. Clozapine reduces mortality from both unnatural and natural causes

Although clozapine can cause weight gain and diabetes, patients on clozapine have a lower mortality rate from things like heart disease.(1)

Chart showing odds ratio of death in patients on an antipsychotic


4. NICE recommends that clozapine should be tried after two antipsychotics have not been effective, but many patients wait longer than this

One study found that on average patients have had 5.6 treatment episodes with 3.9 different drugs before they get clozapine. The mean wait before starting clozapine was around four years. This is a problem, as another study suggested that clozapine may be less effective if treatment is delayed beyond three years.(3)(4)


5. Many patients on clozapine may be on too low a dose

Data from plasma assays showed that more than 40% of patients had a plasma level below the recommended therapeutic range.(6)

Bar graph showing showing patient plasma levels


  1. Hayes et al (2014) Schizophrenia Bulletin, 41(3), 644-655
  2. Taylor et al. (2000) Psychiatric Bulletin; 24(12): 450-452
  3. Howes et al (2012) Br J Psychiatry; 201, 481-485
  4. Yoshimura et al. Psychiatry Res 2017; 250: 65-70
  5. Meyer JM. J Clin Psychopharmacol 2001; 21(6): 569-574
  6. Couchman et al.  Ther Drug Monit 2010; 32(4): 438-447



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