title: Venlafaxine hyponatraemia: incidence, mechanism and management.
abstract: OBJECTIVE
  This prospective study was performed on patients aged >65 years commencing therapy with venlafaxine, in order to determine the incidence of hyponatraemia induced by the drug, to investigate the underlying pathophysiological mechanisms, and to evaluate a simple approach to management of this condition.
  
  
  METHODS
  All patients aged >65 years seen by one author (MR) from all referral sources were entered into the study. Baseline biochemical tests were ordered, and if hyponatraemia developed (plasma Na <130 mmol L(-1)) additional tests were performed to ascertain the mechanism, while the patient continued on venlafaxine and fluid restriction was instituted.
  
  
  RESULTS
  A total of 58 patients were seen, of whom 10 developed hyponatraemia, giving an incidence of 17.2%. Of these 10 patients, five were excluded from prolonged observation because of either severe medical illness, side-effects from the antidepressant or being lost to follow up. When hyponatraemia developed, it invariably did so within a few days of starting venlafaxine, and was associated with non-suppression of antidiuretic hormone in the face of a low serum osmolality. Fluid restriction (800 mL day(-1)) was effective in raising the plasma sodium to the normal range within 2 weeks, after which the fluid restriction could be relaxed without relapse occurring. These patients remained well for the follow-up period of up to 6 months.
  
  
  CONCLUSIONS
  Patients >65 years of age should have their electrolytes measured 3-5 days after starting venlafaxine therapy. If hyponatraemia develops, it can be managed with modest fluid restriction without discontinuing drug treatment, subject to close continued clinical observation and biochemical monitoring.
authors.affiliation: Concord Hospital, Hospital Road, Concord, NSW 2139, Australia. mroxanas@bigpond.net.au
authors.forename: Milton
authors.initials: M
authors.lastname: Roxanas
authors.forename: Emily
authors.initials: E
authors.lastname: Hibbert
authors.forename: Michael
authors.initials: M
authors.lastname: Field
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D018687:Antidepressive Agents, Second-Generation / Q000009:adverse effects* / Q000627:therapeutic use; D003430:Cross-Sectional Studies; D003511:Cyclohexanols / Q000009:adverse effects* / Q000627:therapeutic use; D003866:Depressive Disorder / Q000097:blood / Q000188:drug therapy*; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000139:chemically induced* / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D007177:Inappropriate ADH Syndrome / Q000139:chemically induced* / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D015994:Incidence; D011446:Prospective Studies; D012307:Risk Factors; D012964:Sodium / Q000097:blood; D000069470:Venlafaxine Hydrochloride
chemical_list: D018687:Antidepressive Agents, Second-Generation; D003511:Cyclohexanols; D000069470:Venlafaxine Hydrochloride; D012964:Sodium