88 - Other prescribed drugs

Other prescribed drugs

418 The Maudsley® Prescribing Guidelines in Psychiatry CHAPTER 3 Treatment28 The normal range for serum sodium is 136–145mmol/L. It may be possible to manage mild hyponatraemia (>130  mmol/L) with fluid restriction. Some suggest increasing sodium intake,4 although this is likely to be impractical. If symptoms persist, the antidepressant should be discontinued. ■ ■If serum sodium is >125mmol/L – monitor sodium daily until normal. Symptoms include headache, nausea, vomiting, muscle cramps, restlessness, lethargy, confusion and disorientation. Withdraw the offending antidepressant as soon as possible. ■ ■If serum sodium is <125 mmol/L – refer urgently to specialist medical care. The antidepressant should be discontinued immediately. There is an increased risk of life-­ threatening symptoms such as seizures, coma and respiratory arrest. Over-­rapid correction of hyponatraemia may be harmful. Restarting treatment ■ ■Hyponatraemia may recur on rechallenge with the same or a different SSRI, but may be less likely with an antidepressant from another class.27,31 ■ ■Consider withdrawing other drugs associated with hyponatraemia (risk increases exponentially when antidepressants are combined with diuretics, etc.). ■ ■Prescribe a drug from a different class. Consider noradrenergic drugs such as nortriptyline and lofepramine, or mirtazapine, or an MAOI such as moclobemide. Agomelatine or bupropion32 might also be considered. Begin with a low dose, increase slowly and monitor closely. If hyponatraemia recurs and continued antidepressant use is essential, consider water restriction and/or careful use of demeclocycline. ■ ■Consider (es)ketamine or ECT if a standard antidepressant cannot be given. Other prescribed drugs Carbamazepine has a well-­known association with SIADH33 and antipsychotic use has been linked to hyponatraemia (see section on hyponatraemia in psychosis in Chapter 1). Other commonly prescribed drugs such as thiazide diuretics, opiates, NSAIDs, tramadol, cytotoxics, omeprazole and trimethoprim can also cause hyponatraemia.2,33 References

1. Egger C, et al. A review on hyponatremia associated with SSRIs, reboxetine and venlafaxine. Int J Psychiatry Clin Pract 2006; 10:17–26.
2. Liamis G, et al. A review of drug-­induced hyponatremia. Am J Kidney Dis 2008; 52:144–153.
3. Takeda K, et al. Analysis of the frequency and onset time of hyponatremia/syndrome of inappropriate antidiuretic hormone induced by antidepressants or antipsychotics. Ann Pharmacother 2022; 56:303–308.
4. Kruger S, et al. Duloxetine and hyponatremia: a report of 5 cases. J Clin Psychopharmacol 2007; 27:101–104.
5. Gandhi S, et al. Second-­generation antidepressants and hyponatremia risk: a population-­based cohort study of older adults. Am J Kidney Dis 2017; 69:87–96.
6. Mohan S, et al. Prevalence of hyponatremia and association with mortality: results from NHANES. Am J Med 2013; 126:1127–1137.e1.
7. Selmer C, et al. Hyponatremia, all-­cause mortality, and risk of cancer diagnoses in the primary care setting: a large population study. Eur J Intern Med 2016; 36:36–43.
8. Thomas A, et al. Hyponatraemia and the syndrome of inappropriate antidiuretic hormone secretion associated with drug therapy in psychiatric patients. CNS Drugs 1995; 5:357–369.
9. Movig KL, et al. Serotonergic antidepressants associated with an increased risk for hyponatraemia in the elderly. Eur J Clin Pharmacol 2002; 58:143–148.