BackgroundEvidence is limited regarding the optimal therapeutic approach for neuropsychiatric symptoms associated with Parkinson’s disease dementia (PDD). Selective serotonin reuptake inhibitors (SSRIs) are widely used for mood disorders and behavioral symptoms in older adults with cognitive impairment, but they have limited efficacy in patients with PDD. The effect of SSRIs on hemostasis is also unclear. This report describes a patient with PDD who developed deep venous thrombosis (DVT) and hyponatremia after initiating citalopram treatment.Case presentationAn 86-year-old woman with PDD presented to our emergency department with altered mental status, generalized weakness, and left lower leg swelling. Citalopram was begun 4 weeks previously for behavioral changes and was discontinued 2 days before presentation because of excessive fatigue. At presentation, her plasma sodium level was 123 mg/dL. Brain computed tomography showed age-related changes. Doppler ultrasound revealed a DVT in the left lower leg. The patient was treated with hypertonic saline and intravenous heparin. After normalization of her sodium, she was discharged on donepezil and apixaban. At follow-up, her sodium remained normal, and her cognition and behavior were noticeably improved.ConclusionOlder adults with Parkinson’s disease are sensitive to adverse effects of psychotropic agents, including SSRIs, which are not recommended first-line agents for behavioral symptoms in PDD. Upon initiating SSRIs in older patients with functional decline and multiple comorbidities, physicians need to evaluate the patient’s risk factors for bleeding or thrombosis. Physical activities should also be maintained as much as possible.