The physical health and side-effect monitoring of patients prescribed clozapine: data from a clinical audit conducted in UK mental health services

BACKGROUND: In addition to mandatory haematological monitoring, treatment guidelines recommend routine monitoring of adverse effects and physical health in patients prescribed clozapine. METHODS: NHS trusts/healthcare organisations participated in a clinical audit in the context of a UK quality improvement programme addressing clozapine-prescribing practice. RESULTS: Data relating to 6948 adult patients prescribed clozapine were submitted by 63 NHS trusts/healthcare organisations. Of 481 patients treated with clozapine for up to 18 weeks, there was documented pretreatment screening of blood pressure, heart rate and ECG in at least 90%, and body weight, plasma lipids, plasma glucose/glycated haemoglobin (HbA1c) and physical examination in approximately 80%. During the first 2 weeks of clozapine treatment there was documented daily measurement of both heart rate and blood pressure in 82% and body temperature in 77%. In a subsample of 411 patients, of the 72% who had weekly side-effect assessments documented in the first month of treatment, a structured assessment tool had been used in 29%. Treatment monitoring up to 18 weeks included an ECG in 90%, C-reactive protein (CRP) or creatine kinase in 42%, and troponin or B-type natriuretic peptide (BNP) in 29%. In the 5908 patients prescribed clozapine for at least 1 year, blood pressure and body weight/body mass index were documented in at least 80%, plasma lipids in 78% and plasma glucose in 73%, with an ECG in 55%. Two-thirds were prescribed medication to manage side effects of clozapine and one third of those with a diagnosis of schizophrenia were prescribed a second antipsychotic medication. CONCLUSION: The findings suggest that for most patients treated with clozapine in UK mental health services, physical health screening and side-effect monitoring follow recommended practice, but there was limited use of structured side-effect assessment tools. Monitoring for clozapine-induced myocarditis during the early risk period using markers of inflammation such as CRP, and cardiac damage such as troponin and BNP, was less consistent. This may partly reflect the variation in guideline recommendations for monitoring for myocarditis and partly the selected use of such tests when prompted by cardiac symptoms. The relatively common coprescription of medications for the majority of people on longer-term clozapine treatment may well further increase side-effect burden and physical health risks, reinforcing the need for continuing systematic monitoring.