Dr. Arthi Gauthaman^1*, Dr. Jaganathan Selvanayagam¹, Dr. Rahul S M²

Dr. Arthigauthaman MBBS, MD, Adult Intensive care unit, Dr Mehtas multi-speciality Hospital, Chennai, Tamil Nadu, India, Email: arthi85med@gmail.com; ORCID ID: 0000-0001-5544-9604

Dr. Jaganathan Selvanayagam MBBS, MD, EDIC, Adult Intensive care unit, Dr Mehtas Multi-speciality Hospital, Chennai 600034, TamilNadu, India, Email: jaganmmc@gmail.com

Dr. Rahul S M MBBS, FCCM, Adult Intensive care unit Dr Mehtas Multi-speciality Hospitals, Chennai 600034, TamilNadu, India, Email: drrahulsm23@gmail.com; ORCID ID: 0009-0008-5974-2291

Corresponding Author & Copyrights: Dr. Arthigauthaman MBBS, MD, Adult Intensive care unit, Dr Mehtas multi-speciality Hospital, Chennai, Tamil Nadu, India, Email: arthi85med@gmail.com; ORCID ID: 0000-0001-5544-9604.

Citation: Dr. Arthi Gauthaman, Dr. Jaganathan Selvanayagam, Dr. Rahul S M (2026) Linezolid Associated Serotonin Syndrome Presenting as Persistent Fever in an Elderly Woman with Dementia, Diabetes and Chronic Lacunar Infarcts: A Case Report. World J Case Rep Clin Imag. 2026 August; 5(2),1-6.

Copyrights © Dr. Arthi Gauthaman, et al., 2026, This article is licensed under the Creative Commons Attribution-Non Commercial-4.0-International-License-(CCBY-NC) (https://worldjournalofcasereports.org/blogpage/copyright-policy). Usage and distribution for commercial purposes require written permission.

Abstract:

Background and Objectives: Linezolid, a reversible non-selective monoamine oxidase inhibitor, is widely used for multidrug-resistant Gram-positive infections but can precipitate serotonin syndrome, particularly when combined with other serotonergic agents such as ondansetron. In critically ill patients, persistent fever is often presumed to be infectious, leading to unnecessary escalation of antimicrobial therapy. This report highlights linezolid-associated serotonin syndrome presenting as fever of unknown origin in an elderly ICU patient.

Methods: A 75-year-old woman with dementia, psychosis, diabetes mellitus, and chronic lacunar infarcts was admitted with multidrug-resistant Escherichia coli urosepsis followed by MRSA pneumonia. During hospitalization, she was receiving ondansetron 8 mg twice daily, lorazepam 1 mg twice daily, and bromocriptine 2.5 mg once daily, without concurrent antipsychotic therapy. After 7 days of colistin and fosfomycin, antimicrobial treatment was changed to meropenem and linezolid. On the seventh day of linezolid therapy, she developed persistent high-grade fever, autonomic instability (tachycardia, labile blood pressure, diaphoresis), and neuromuscular hyperactivity (tremor, rigidity, hyperreflexia). Repeat cultures, inflammatory markers, and procalcitonin were negative. The patient fulfilled the Hunter Serotonin Toxicity Criteria, prompting suspicion of linezolid-associated serotonin syndrome. Linezolid was discontinued, while ondansetron and bromocriptine were continued.

Results: Following withdrawal of linezolid, the patient's fever resolved within 3 days, with marked improvement in autonomic and neuromuscular manifestations. No alternative infectious sources were identified, supporting the diagnosis of linezolid-associated serotonin syndrome.

Conclusion: Linezolid-associated serotonin syndrome should be considered in elderly ICU patients with persistent fever, autonomic instability, and neuromuscular abnormalities, particularly when concomitant serotonergic agents such as ondansetron are being administered. Early recognition using the Hunter Serotonin Toxicity Criteria and prompt withdrawal of the offending drug can prevent unnecessary diagnostic investigations and inappropriate escalation of antimicrobial therapy.