Starting with this issue, Editor-in-Chief Chris Aiken, MD, will give advice on a different practice challenge. If you have a question you’d like Dr. Aiken to answer, please send an email to AskTheEditor@thecarlatreport.com.

Dr. Aiken won’t be able to answer all questions received, but he will pick one each month that is of general interest.

Medication-Induced Hyponatremia
Dear Dr. Aiken: Can you tell us more about hyponatremia? Which medications can cause hyponatremia, who’s at risk, and how we should manage this condition?

Dr. Aiken: Hyponatremia, or low sodium level, is a rare but serious side effect of certain psychiatric medicines. The following is some information that I hope will help:

Which medications cause hyponatremia?
Oxcarbazepine (30% for mild; 1.3% for significant) and carbamazepine (15% mild; 0.1% significant). SSRIs, SNRIs, and antipsychotics cause hyponatremia at much lower rates (around 1:2,000).

Who’s at risk?
Age >45, thiazide diuretic use, renal or kidney disease. Hyponatremia is common in schizophrenia (lifetime rate 10%) due in part to psychogenic polydipsia, a psychotic syndrome where patients drink water compulsively.

What are the symptoms?
Nausea, dizziness, memory problems, malaise, fatigue, and headaches. Usually the drop in sodium is gradual, causing mild symptoms, but the presentation can be dramatic when the sodium falls over a few days. Either way, hyponatremia has serious consequences if left untreated: seizures, rhabdomyolysis, brain stem myelinolysis, and death.

How do you interpret the level?
Decreased sodium can be mild (<135 Meq/L) or severe (<125 Meq/L).

Management tips
If sodium <125 Meq/L or the symptoms are severe, send to ED. Otherwise, stop the causative medication, restrict fluids (1–1.5 L/day), and recheck sodium in 1 week. Lithium levels can rise during hyponatremia, so hold that medicine and check a level if the patient is taking it. Refer to nephrology if the problem persists. When the offending medication can’t be stopped, the ADH inhibitor demeclocycline (600–1200 mg/day) can be added in consultation with nephrology.

Sources: Yang HJ et al, Psychopharmacology (Berl) 2017;234(5):869–876. Annamalai A, Medical Management of Psychotropic Side Effects. New York, NY: Springer; 2017.