Successful rechallenge with clozapine after discontinuation due to drug‐induced pneumonia: A case report

• Published in: PCN reports Vol. 1; no. 3; pp. e38 - n/a
• Main Authors: Kikuchi, Yuki, Komatsu, Hiroshi, Sakuma, Atsushi, Tanifuji, Hiroaki, Tomita, Hiroaki
• Format: Journal Article
• Language: English
• Published: Australia John Wiley & Sons, Inc 01.09.2022; John Wiley and Sons Inc; Wiley
• Subjects: adverse effects; Aspergillosis; Asthma; Bacterial infections; Blood tests; Case Report; Case Reports; clozapine; Coronaviruses; Drug dosages; Fever; Hallucinations; Infections; Influenza; Kinases; Leukocytes; Lungs; Myocarditis; Patients; Pneumonia; rechallenge; Schizophrenia; Viral infections; Japan; adverse effects; clozapine; rechallenge; schizophrenia; pneumonia
• ISSN: 2769-2558; 2769-2558
• DOI: 10.1002/pcn5.38

Background There have been a limited number of case reports of clozapine‐induced pneumonia. Few have reported rechallenging of clozapine after discontinuation due to the side‐effect. Case Presentation A 43‐year‐old man was diagnosed with schizophrenia after developing auditory hallucinations and delusions of persecution and reference. After diagnosing him with treatment‐resistant schizophrenia, clozapine was started. From a starting dose of 12.5 mg/day, we increased it by 25 mg every 2–3 days to reach 150 mg/day by Day 15. On Day 17, his body temperature suddenly rose to 39.6°C (103.3°F) without any other apparent physical symptoms. Blood biochemistry testing showed elevated C‐reactive protein (CRP) and high counts of leukocytes and neutrophils, but not eosinophils. Chest computed tomography revealed ground‐glass opacities in the lower lobes of both lungs. Suspecting bacterial pneumonia, we started him on levofloxacin 500 mg/day. However, pneumonia exacerbated, and eosinophilia became apparent 5 days after the onset of fever. We suspected acute eosinophilic pneumonia induced by clozapine and discontinued its administration the same day. The patient clinically recovered the next day after stopping clozapine. After stopping clozapine, his psychiatric symptoms, such as persecutory/referential delusions, irritability, and polydipsia, became worse. We decided to rechallenge with clozapine in incremental doses slower than the standard protocol, along with careful monitoring of CRP and eosinophil counts. Pneumonia has not recurred, and his psychiatric symptoms have been well managed. Conclusion Our experience suggests that some patients with inflammatory reactions to clozapine can still take the drug if it is reintroduced with caution. This study highlights the clinical course and management of a patient diagnosed with schizophrenia in whom clozapine was discontinued due to the development of drug‐induced pneumonia but was later rechallenged successfully. Our case suggests that some patients who have inflammatory reactions to clozapine can still take the drug—after a temporary recovery period—if it is reintroduced with caution and care.