{
  "abstract": "Background and Importance Serotonin syndrome (SS) is a rare but potentially life-threatening condition caused by excessive serotonergic activity, usually triggered by drug interactions; in renal insufficiency, drugs and metabolite accumulation may exacerbate it. Diagnosis in older patients is especially challenging, as atypical presentations and cognitive impairment can obscure recognition. Hospital pharmacists play a decisive role by identifying drug-related risks, supporting early diagnosis, and guiding therapy.Aim and Objectives To present the case of a 78-year-old man with stage 5 chronic kidney disease on haemodialysis and multimorbidity (diabetes mellitus with microangiopathy and recurrent foot infections, epilepsy on levetiracetam, ischaemic heart disease, prior gastrointestinal bleeding and chronic anaemia) and polypharmacy, admitted following a recent course of antibiotics. The patient had experienced previous episodes of transient neurological symptoms with negative stroke workup and levetiracetam adjustment.Material and Methods On admission, he presented with slurred speech and aphasia, without fever or trauma. Initial cranial CT excluded acute stroke, and levetiracetam dose was decreased (500 mg/48h) as it can cause lethargy. Within 24h, he deteriorated to stupor (Glasgow Coma Scale 4), responding only to painful stimuli, with generalised rigidity. Repeat CT again excluded acute pathology. Differential diagnosis included seizure, metabolic encephalopathy, drug-induced toxicity, and infection. Laboratory tests revealed hyperkalaemia (8.6 mmol/L), elevated lactate (73 mg/dL), leukocytosis (13.24 ×10 9/L), and normal creatin kinase (54 U/L). Medication review revealed concurrent treatment with linezolid, sertraline and fentanyl. Naloxone was ineffective, prompting discontinuation of linezolid, sertraline, and fentanyl; raising suspicion of SS.Results Following discontinuation of serotonergic agents, the patient progressively improved, regaining consciousness, verbal responsiveness, and mobility within 48h. Other diagnoses were excluded, and SS was diagnosed clinically as an exclusion, supported by recovery after drug withdrawal.Conclusion and Relevance This case illustrates the complexity of diagnosing SS in elderly patients, where nonspecific symptoms, multimorbidity, and cognitive impairment hinder early recognition. Polypharmacy and altered pharmacokinetics increase vulnerability to drug interactions. Medication reviewed by hospital pharmacists is decisive for establishing the diagnosis and achieving recovery. Early recognition and prompt withdrawal of causative drugs are essential to prevent complications and reduce morbidity and mortality. Increased awareness among clinicians and hospital pharmacists is crucial to improve safety and prevent SS in this vulnerable population.Conflict of Interest No conflict of interest",
  "authors": [
    {
      "affiliations": [
        "Parc Taulí Hospital Universitari, Hospital Pharmacy, Sabadell, Spain"
      ],
      "name": "AJ Reyner Parra"
    },
    {
      "affiliations": [
        "Parc Taulí Hospital Universitari. Institut D’investigació I Innovació Parc Taulí I3pt-Cerca, Hospital Pharmacy, Sabadell, Spain"
      ],
      "name": "I Gozalo Esteve"
    },
    {
      "affiliations": [
        "Hospital Universitari Vall D’hebron, Hospital Pharmacy, Barcelona, Spain"
      ],
      "name": "P Martínez Puig"
    },
    {
      "affiliations": [
        "Parc Taulí Hospital Universitari. Institut D’investigació I Innovació Parc Taulí I3pt-Cerca, Unitat Geriàtrica D’aguts, Sabadell, Spain"
      ],
      "name": "I Torrente Jimenez"
    },
    {
      "affiliations": [
        "Parc Taulí Hospital Universitari. Institut D’investigació I Innovació Parc Taulí I3pt-Cerca, Hospital Pharmacy, Sabadell, Spain"
      ],
      "name": "A Pérez Contel"
    },
    {
      "affiliations": [
        "Parc Taulí Hospital Universitari. Institut D’investigació I Innovació Parc Taulí I3pt-Cerca, Hospital Pharmacy, Sabadell, Spain"
      ],
      "name": "R Bueno Uceda"
    },
    {
      "affiliations": [
        "Parc Taulí Hospital Universitari. Institut D’investigació I Innovació Parc Taulí I3pt-Cerca, Hospital Pharmacy, Sabadell, Spain"
      ],
      "name": "L Hernández Rodríguez"
    },
    {
      "affiliations": [
        "Parc Taulí Hospital Universitari. Institut D’investigació I Innovació Parc Taulí I3pt-Cerca, Hospital Pharmacy, Sabadell, Spain"
      ],
      "name": "M Gómez-Valent"
    }
  ],
  "title": "5PSQ-166 Serotonin syndrome in an elderly patient: a case report",
  "uid": "5d196a79-c282-53e3-ad69-45e6f9df5f6f"
}