Psychosomatics 43:3, May-June 2002 241 Copyright  2002 The Academy of Psychosomatic Medicine. A Case of SIADH and Hyponatremia Associated With Citalopram JAMES A. BOURGEOIS, M.D., SARAH E. BABINE, M.D., NEHA BAHADUR, M.D. Received October 16, 2001; revised December 4, 2001; accepted January 31, 2002. From the Department of Psychiatry, University of California, Davis, 2230 Stock- ton Boulevard, Sacramento, California 95817. Address correspondence and re- print requests to Dr. Bourgeois, Department of Psychiatry, University of Cali- fornia, Davis, 2230 Stockton Boulevard, Sacramento, CA 95817; E-mail: James.bourgeois@ucdmc.ucdavis.edu. W e report a case of hyponatremia due to the syn- drome of inappropriate antidiuretic hormone (SIADH) following citalopram use. The patient improved with discontinuation of citalopram and self-correction of his hyponatremia. Physicians prescribing SSRIs should be aware of this infrequent but significant side effect. Case Report An elderly white male presented with visual hallucinations, paranoid delusions, forgetfulness, agitation, and suicidal and homicidal ideation. Citalopram 10 mg po qd had been pre- scribed following diagnoses of ‘‘anxiety and depression’’ by his primary care physician. His symptoms worsened markedly after beginning citalopram. He was noted to have had a serum sodium level of 126 mEq/L following the onset of his symp- toms. He had stopped the citalopram several days before pre- sentation. Medical history included coronary artery disease with myocardial infarction, prostatic hypertrophy with transurethral resection of the prostate, hypertension, hyperlipidemia, hypo- thyroidism, oropharyngeal carcinoma, and urinary tract infec- tion. Physical examination and CT of the head were unremark- able. Serum sodium was 131 mmol/L, serum osmolality 275 mOsm/kg, urine osmolality 460 mOsm/kg, and urine sodium 131 mmol/L. Citalopram was held; serum sodium levels were monitored. Serum sodium increased to 134 mmol/L by the day of psychiatric interview, 3 days after admission. He was pleasant, cooperative, and able to discuss past events in a logical man- ner. Mood was euthymic; affect was congruent. Thought pro- cesses were linear with some tangentiality. He denied suicidal/ homicidal ideations, hallucinations, and delusions. Cognitive testing revealed time disorientation, mild deficits in recall memory, and poor concentration. Mini-Mental Status Exami- nation (MMSE) score was 21/30. Psychiatric diagnoses were delirium, secondary to hyponatremia, resolving, and rule out dementia, vascular subtype, mild. Discussion Hyponatremia (serum sodium 135 mmol/L) has been reported with SSRIs. 1,2 Risk factors include increased age, female gender, smoking, low body weight, tumors, respi- ratory or CNS illnesses, previous episodes of hyponatre- mia, and other medications (particularly diuretics). 1,3 The mechanism is through the syndrome of inappropriate se- cretion of antidiuretic hormone (SIADH), resulting in an euvolemic hyponatremia with low serum and high urine osmolalities. 3,4 Patients may present with fatigue, weak- ness, and apathy, which may simulate worsening depres- sion. 5 Mild hyponatremia generally reverses following medication discontinuation; fluid restriction may be ad- vised. 5 Severe hyponatremia may need IV normal or hy- pertonic saline, though excessively rapid correction may induce heart failure or central pontine myelinosis. 5 Some may benefit from demeclocycline. 5 Inaguma et al. reported three cases 3–90 days after beginning fluvoxamine. 4 Their patients presented with coma, serum sodium 103–112 mmol/L, serum osmolality 227–241 mOsm/kg, urine osmolality 352–781 mOsm/kg, and urine sodium 38–107 mmol/L. They improved fol- lowing hypertonic saline. Romerio et al. reported a case with seizures 10 days after beginning fluoxetine. 2 Bouman et al. reported an incidence of symptomatic SIADH of 12.5% in elderly inpatients receiving SSRIs (4 cases in 32 patients); four other patients had asymptomatic SIADH. 6 Leung et al. reported two cases. 5 The first case presented with serum sodium 123 mmol/L, serum osmo- lality 252 mOsm/kg, urine osmolality 420 mOsm/kg, and urine sodium 38 mmol/L, 10 days after starting paroxe-