Clozapine-Induced Myocarditis More Common Than Thought
New research indicates that myocarditis, inflammation of the middle layer of the heart wall, occurs in about 3% of patients who begin taking clozapine (Clozaril). Researcher Kathlyn J. Ronaldson and colleagues recently published research to this effect in the journal Acta Psychiatrica Scandinavica. Many cases of myocarditis, which can be fatal, begin with fever. Other symptoms include rapid or abnormal heart rhythms, shortness of breath, fluid retention, and fatigue. Because the illness resembles a viral infection, it may be misdiagnosed.
In 2010 Ronaldson and colleagues reported in the Journal of Clinical Psychiatry that tachycardia (rapid resting heart rate) and elevated levels of a group of proteins knows as troponin in the blood are almost always present during the first 45 days of treatment in patients who develop myocarditis. The researchers found that the time to onset of myocarditis was 14 to 22 days in almost all cases. Eosinophilia (high levels of a certain type of white blood cell) may occur in the week after peak troponin levels, and high levels of the inflammatory protein CRP (above 100mg/L) occurred in 79% of cases.
Ronaldson and colleagues suggest that patients who are prescribed clozapine be monitored for myocarditis during the first four weeks of treatment, particularly during the third week.