What is the management for hyponatremia in patients taking olanzapine?

Management of Olanzapine-Induced Hyponatremia

Immediate Action and Monitoring

Discontinue olanzapine immediately if hyponatremia develops, as this is a rare but potentially life-threatening complication that can progress rapidly to seizures and require ICU admission 1, 2.

• Monitor serum sodium levels closely, as olanzapine-associated hyponatremia can develop within days to weeks of initiation and may deteriorate rapidly 1, 2
• Check baseline sodium before starting olanzapine and monitor periodically during the first month, as most cases occur early in treatment 3
• Assess for severe symptoms (confusion, seizures, altered mental status) that require emergent intervention 2

Diagnostic Workup

Evaluate for SIADH versus psychogenic polydipsia, as both mechanisms can cause hyponatremia in psychiatric patients on olanzapine 2:

• Measure serum and urine osmolality, urine sodium concentration, and assess volume status 4
• Urine osmolality >100 mOsm/kg with urine sodium >20 mEq/L suggests SIADH 4
• Assess for clinical euvolemia (no edema, normal blood pressure, moist mucous membranes) which supports SIADH 4
• Rule out other causes: check thyroid function (TSH), cortisol, and review all medications including diuretics 4

Treatment Based on Severity

For Severe Symptomatic Hyponatremia (seizures, altered mental status):

• Administer 3% hypertonic saline immediately with a goal to increase sodium by 6 mmol/L over 6 hours or until symptoms resolve 4
• Give 100 mL boluses of 3% saline over 10 minutes, repeatable up to three times at 10-minute intervals 4
• Do not exceed total correction of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 4
• Monitor sodium levels every 2 hours during active correction 4
• Consider ICU admission for close monitoring 4

For Mild to Moderate Asymptomatic Hyponatremia:

• Implement fluid restriction to 1 L/day as first-line treatment if SIADH is confirmed 4
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction alone 4
• Monitor sodium levels every 4 hours initially, then daily 4

Correction Rate Guidelines

Limit correction to maximum 8 mmol/L per 24 hours in all patients 4:

• For chronic hyponatremia (>48 hours duration), aim for slower correction of 4-6 mmol/L per day 4
• If overcorrection occurs, immediately switch to D5W and consider desmopressin to relower sodium 4
• Watch for osmotic demyelination syndrome signs (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) occurring 2-7 days post-correction 4

Risk Factor Assessment

Identify high-risk patients before starting olanzapine 3, 5:

• Advanced age and female gender increase risk 3
• Concomitant thiazide diuretics significantly elevate risk 3
• Baseline sodium in lower normal range (<135 mmol/L) 3
• Low body weight 3
• Concurrent use of SSRIs (paroxetine, citalopram, escitalopram) or other antipsychotics 3, 5

Alternative Antipsychotic Selection

• Consider switching to an antipsychotic with lower hyponatremia risk once sodium normalizes 1, 2
• Avoid polypharmacy with multiple psychotropics, as this increases adverse event risk 5
• Do not rechallenge with olanzapine after documented hyponatremia episode 1

Common Pitfalls to Avoid

• Failing to monitor sodium levels in psychiatric patients, as they may not report symptoms or symptoms may be attributed to psychiatric illness 1
• Continuing olanzapine despite mild hyponatremia, as progression can be rapid and severe 2
• Overly rapid correction exceeding 8 mmol/L in 24 hours, risking osmotic demyelination 4
• Missing concomitant risk factors (diuretics, SSRIs) that compound hyponatremia risk 3, 5
• Attributing confusion or altered mental status solely to psychiatric disease rather than investigating metabolic causes 1