Hyponatremia—low sodium levels in the blood—is one of the most common medical complications in older adults. Even a mild drop in sodium can cause confusion, dizziness, unsteadiness, irritability, falls, and hospitalisation. In severe cases, it can trigger seizures or life-threatening brain swelling.

What many families and even clinicians overlook is that psychiatric medications are among the biggest contributors to hyponatremia in the elderly.

As India’s ageing population grows and more seniors seek treatment for depression, anxiety, insomnia, bipolar disorder, dementia-related behaviours or psychosis, understanding this risk becomes essential.

This article compares how different psychiatric medications influence sodium levels and offers guidance on safer prescribing for older adults.

Why Older Adults Are More Vulnerable to Hyponatremia

Ageing brings several physiological changes:

• Reduced kidney function

• Increased sensitivity to medications

• Lower thirst sensation

• Higher risk of dehydration

• Changes in hormone regulation (SIADH risk increases)

• More comorbidities and polypharmacy

When psychiatric medications are added to this mix, sodium levels can drop rapidly—sometimes within days.

Psychiatric Medications That Cause Hyponatremia: A Risk Comparison

Below is a practical hierarchy, written specifically for older adults and their caregivers.

1. Highest Risk: SSRIs and SNRIs (the most common offenders)

These antidepressants frequently cause SIADH (Syndrome of Inappropriate ADH Secretion), leading to water retention and sodium dilution.

SSRIs (High Risk)

• Sertraline (Zoloft, Serlift)

• Fluoxetine (Prozac, Flunil)

• Escitalopram (Lexapro, Nexito, Cipralex)

• Citalopram (Citadep, Cipram)

• Paroxetine (Paxil, ParoCR) – particularly strong SIADH risk

• Fluvoxamine (Fluvoxin)

SNRIs (Moderate to High Risk)

• Venlafaxine (Venlor, Effexor) – well-known for causing hyponatremia

• Duloxetine (Duzela, Cymbalta)

Elderly patients starting these medications should have sodium levels checked at baseline, after 2 weeks, and again at 1 month.

2. Moderate Risk: Carbamazepine & Oxcarbazepine (Mood Stabilizers)

These drugs can directly induce SIADH and are notorious for causing even severe hyponatremia.

• Carbamazepine (Tegretol, Zeptol, Mazetol)

• Oxcarbazepine (Trileptal, Oxetol) – even higher risk than carbamazepine in some studies

They are effective mood stabilisers but need vigilant monitoring in the elderly.

3. Moderate Risk: Antipsychotics

Some antipsychotics can trigger SIADH or worsen water imbalance due to sedation and increased water intake.

Higher-risk antipsychotics

• Risperidone (Risnia, Sizodon)

• Haloperidol (Serenace, Haldol)

• Olanzapine (Oleanz, Olanex)

• Quetiapine (Qutan, Quepin)

Lower-risk but still reported

• Aripiprazole (Arpizol, Abilify)

• Lurasidone (Lurace, Latuda)

• Ziprasidone (Zipsydon)

Antipsychotic-associated hyponatremia often presents subtly: more confusion, increased falls, irritability—symptoms mistakenly attributed to “worsening dementia.”

4. Lower to Moderate Risk: Benzodiazepines & Z-Drugs

These do not directly cause SIADH, but in older adults they can:

• increase water intake during sedation

• worsen confusion → dehydration cycles

• indirectly precipitate low sodium

Includes:

• Clonazepam (Rivotril)

• Lorazepam (Ativan)

• Diazepam (Valium)

• Zolpidem (Stilnoct, Zolfresh)

5. Mood Stabilizers With Low Hyponatremia Risk

Relatively safer options:

• Lithium (though it has other risks like renal impairment)

• Lamotrigine (Lamitor, Lamictal)

Both are less likely to cause SIADH, but require monitoring for other complications.

How Hyponatremia Shows Up in Older Adults

Many caregivers confuse early hyponatremia symptoms with “dementia worsening”:

• Increased forgetfulness

• Dizziness

• Unsteady gait

• Irritability

• Excessive sleepiness

• Slurred speech

• Confusion or disorientation

• Nausea or vomiting

• Frequent falls

• Seizures (in severe cases)

If these appear within 1–4 weeks of starting or increasing a psychiatric medication, sodium should be checked immediately.

A Simple Rule: Elderly + New Psychiatric Medication = Monitor Sodium

Checking sodium is inexpensive, widely available, and can prevent ICU admissions.

Recommended monitoring schedule for high-risk medications:

• Before starting treatment

• 2 weeks after starting

• 1 month after starting

• Every 3–6 months thereafter

This is especially important if the person also takes:

• Diuretics

• ACE inhibitors

• ARBs

• Antiepileptics

• Desmopressin

• Pain medications like tramadol

All of which further increase hyponatremia risk.

Safer Prescribing Strategies for Older Adults

1. Choose antidepressants with lower SIADH risk

• Mirtazapine

• Bupropion

Both are generally safer for sodium levels.

2. Avoid polypharmacy whenever possible

Multiple medicines mean compounded risk.

3. Maintain hydration balance

Not too much, not too little—steady intake helps stabilise sodium.

4. Educate caregivers on early warning signs

Prompt detection is life-saving.

5. Review medications every 3 months

Deprescribing is often the best hyponatremia prevention.

Final Takeaway

Hyponatremia is one of the silent killers of older adults—especially those on psychiatric medications.
The good news?
It is entirely preventable with awareness, early testing, and thoughtful prescribing.

Choosing the right medicine and monitoring sodium levels can help older adults stay safer, clearer and more independent.

Author & Contact

Dr. Srinivas Rajkumar T, MD (AIIMS), DNB, MBA (BITS Pilani)
Consultant Psychiatrist & Neurofeedback Specialist
Mind & Memory Clinic, Apollo Clinic Velachery (Opp. Phoenix Mall)
 srinivasaiims@gmail.com  +91-8595155808