Can Risperidone (risperidone) cause hyponatremia?

Risperidone and Hyponatremia

Yes, risperidone can cause hyponatremia through syndrome of inappropriate antidiuretic hormone secretion (SIADH), and clinicians should monitor sodium levels in patients taking this medication, especially in older adults and those with risk factors.

Mechanism and Evidence

Risperidone has been documented to cause hyponatremia through SIADH, similar to other psychotropic medications. Case reports have established this association:

• A case study reported a patient who developed SIADH following initiation of risperidone and carbamazepine, with successful treatment achieved by discontinuing the medications and implementing fluid restriction 1
• Another case report described a 48-year-old male who developed generalized seizures, hyponatremia, respiratory failure, and rhabdomyolysis seven days after starting risperidone with no other medications 2

Risk Factors for Risperidone-Induced Hyponatremia

Several factors increase the risk of developing hyponatremia with risperidone:

• Age: Older adults are at significantly higher risk 3, 4
• Gender: Female patients appear more susceptible 4
• Concomitant medications: Particularly diuretics 4
• Low body weight: Increases risk of hyponatremia 4
• Lower baseline sodium: Patients with borderline sodium levels are at higher risk 4
• Polydipsia: Common in psychiatric patients, especially those with schizophrenia 5

Clinical Presentation and Monitoring

Hyponatremia typically develops within the first few weeks of treatment with risperidone. The FDA label specifically mentions that seizures occurred in 0.3% of risperidone-treated patients, with two cases associated with hyponatremia, and advises caution in patients with a history of seizures 6.

Symptoms of hyponatremia may include:

• Headache
• Confusion
• Lethargy
• Seizures (in severe cases)
• Nausea and vomiting
• Muscle cramps

Monitoring Recommendations

• Monitor serum sodium levels before initiating risperidone
• Repeat measurements during the first 2-4 weeks of treatment 7
• More frequent monitoring for patients with risk factors
• Be vigilant for clinical signs of hyponatremia

Management of Risperidone-Induced Hyponatremia

When hyponatremia is detected:

1. Mild cases: Consider water restriction and close monitoring
2. Moderate to severe cases:
   • Discontinue risperidone
   • Implement fluid restriction
   • Consider loop diuretics for isovolemic hyponatremia
   • Severe cases may require hypertonic saline 4

Alternative Antipsychotics

If a patient develops hyponatremia on risperidone, consider switching to an alternative antipsychotic with potentially lower risk:

• Clozapine has been successfully used in patients who developed hyponatremia with other antipsychotics 1, 7
• Consider monitoring sodium levels even after switching medications, as hyponatremia can recur with other antipsychotics 5

Clinical Pearls and Pitfalls

• Hyponatremia with antipsychotics may be more common than currently recognized 5
• The American Geriatrics Society Beers Criteria identifies tramadol as associated with hyponatremia/SIADH but does not specifically list risperidone 3
• Patients with schizophrenia (70% of reported cases) may have higher risk due to comorbid polydipsia 5
• The onset of hyponatremia is typically within the first few weeks of treatment but can vary

Remember that early detection through appropriate monitoring is key to preventing serious complications of hyponatremia such as seizures and respiratory failure.