Severe Delirium Caused by Short-Term Administration of Compound Paracetamol and Amantadine Hydrochloride Capsules in an Elderly Patient With Extremely Low Body Weight

This study aimed to investigate the clinical characteristics, underlying mechanisms, and management strategies for severe central nervous system (CNS) toxicity caused by amantadine-containing compound cold medication in elderly patients with extremely low body weight. We report the case of an 83-year-old male patient weighing 37 kg (BMI 13.6 kg/m²) with a normal estimated glomerular filtration rate (eGFR), who presented with severe delirium, visual hallucinations, stereotyped behaviors, and aggressive actions after self-medicating with compound paracetamol and amantadine hydrochloride capsules (cumulative amantadine dose 800 mg) for five days to treat an upper respiratory tract infection. Detailed history-taking, physical examination, and auxiliary tests excluded alternative causes. Following medication discontinuation, full fluid replacement, and symptomatic treatment with low-dose olanzapine (2.5-5 mg/day), the patient's mental and behavioral symptoms completely resolved by day 11, with the Nursing Delirium Screening Scale (Nu-DESC) score decreasing from 10 to 0. The Naranjo score of 7 indicated that the adverse reaction was very likely related to amantadine. Advanced age (≥80 years) and extremely low body weight (BMI<15 kg/m²) may be key risk factors for amantadine-induced CNS toxicity. These factors can lead to rapid drug accumulation, even in patients with normal renal function. Therefore, clinicians should exercise caution in prescribing amantadine-containing medications to high-risk populations and enhance medication safety education.