If antidepressant-induced hyponatraemia has been diagnosed, how should the depression be treated?

This Medicines Q&A evaluates the evidence available on the management of depression in patients with antidepressant-induced hyponatraemia.

Summary

  • Most antidepressants are associated with hyponatraemia, with the highest risk being with SSRIs.
  • If the hyponatraemia is mild (125-134mmol/litre serum sodium) and there is no other cause for the hyponatraemia, discontinue the antidepressant and monitor serum sodium levels daily until they are within normal range or if asymptomatic, consider fluid restriction.
  • If the patient has serum sodium below 125mmol/litre, discontinue the antidepressant immediately and treat medically for hyponatraemia.
  • After serum sodium levels have normalised, choose another appropriate antidepressant.
  • If the patient developed hyponatraemia whilst on an SSRI or venlafaxine, consider changing to a TCAD or a MAOI or mirtazapine. The increased risk of overdose, adverse effects, and drug interactions of these antidepressants must be considered before prescribing. Agomelatine may also be considered. Monitor serum sodium levels weekly initially.
  • Consider ECT if none of these options are appropriate, or the patient still remains hyponatraemic while on antidepressant therapy.

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