Drugs That Can Cause Hyponatremia (Low Sodium)

Dozens of commonly prescribed medications can lower your blood sodium to dangerous levels, a condition called hyponatremia. Thiazide diuretics are the single most frequent pharmaceutical cause, but antidepressants, anti-seizure medications, proton pump inhibitors, pain relievers, antipsychotics, and even some cancer drugs all carry measurable risk. Most of these drugs converge on a shared mechanism involving how your kidneys handle water, yet the specific pathways and risk profiles differ enough that understanding each class matters.

Thiazide Diuretics

If one drug class deserves the spotlight for causing low sodium, it is the thiazides. Hydrochlorothiazide, chlorthalidone, and indapamide are prescribed to millions of people for high blood pressure, and they are consistently the leading pharmaceutical cause of hyponatremia. These drugs work by blocking sodium and chloride reabsorption in a specific segment of the kidney, which interferes with the kidney’s ability to produce dilute urine.¹ The practical result is that your body retains more water relative to the sodium it holds, diluting the sodium concentration in your blood.

The risk is highest in the first few weeks after starting a thiazide and then gradually declines to a lower but still elevated level after about three months. Several mechanisms layer on top of each other: reduced delivery of fluid to the diluting segment of the kidney, lower solute loads, and increased water permeability in the collecting duct driven by some combination of antidiuretic hormone and possibly the drug itself.² Loop diuretics like furosemide, by contrast, do not typically cause hyponatremia and may even reduce the risk, because they act on a different part of the kidney that preserves diluting capacity.

Antidepressants

Selective serotonin reuptake inhibitors, the class that includes fluoxetine, sertraline, citalopram, and escitalopram, are among the most widely recognized non-diuretic causes of drug-induced hyponatremia. The mechanism involves the neurotransmitter norepinephrine. Normally, norepinephrine stimulates the release of antidiuretic hormone (ADH) and is then broken down, ending the signal. SSRIs inhibit norepinephrine reuptake, which allows the signal to persist and causes excess ADH release.³ That extra ADH tells your kidneys to hold onto water, and the resulting dilution drops your sodium.

Other antidepressant classes can do the same. Serotonin-norepinephrine reuptake inhibitors (SNRIs) like venlafaxine and duloxetine carry a similar profile, and older tricyclic antidepressants have also been linked to hyponatremia, though SSRIs remain the most studied. Older age stands out as a strong risk factor for antidepressant-induced hyponatremia, with one review finding an odds ratio of roughly 6 for older patients.⁴ Symptoms tend to appear within the first few weeks of starting the medication, mirroring the thiazide pattern.

Anti-Seizure Medications

Carbamazepine and its close relative oxcarbazepine are the anticonvulsants most strongly tied to hyponatremia. Carbamazepine appears to alter how the brain’s osmoreceptors sense sodium concentration, essentially tricking the body into behaving as though sodium levels are already adequate when they are dropping. An increased sensitivity of the kidney tubules to circulating ADH may also play a role.⁵

Oxcarbazepine is interesting because its mechanism seems distinct. When researchers tested it against a water load challenge, sodium levels dropped and the kidney’s ability to clear free water declined, yet ADH levels did not rise. That finding suggests oxcarbazepine does not cause the classic syndrome of inappropriate ADH secretion but instead acts directly on the kidney’s collecting tubules or makes them more responsive to whatever ADH is already circulating.⁶ This distinction matters clinically because treatment strategies that focus on suppressing ADH may not work as well for oxcarbazepine-induced cases.

Pain Medications

Nonsteroidal anti-inflammatory drugs like ibuprofen, naproxen, and ketorolac can push sodium levels down through a straightforward mechanism. In the kidney, prostaglandins normally act as a brake on ADH’s water-retention effects. NSAIDs suppress prostaglandin production, which removes that brake and lets ADH work unchecked.⁷ The result is increased water reabsorption and diluted sodium.⁸

Because NSAIDs are available over the counter, many people take them without considering electrolyte effects. On their own, NSAIDs rarely cause severe hyponatremia in healthy young adults. The risk escalates in older people, in those already taking other offending medications, and when NSAID use is prolonged rather than occasional. Worth noting: the same prostaglandin-suppressing action that causes water retention also contributes to the kidney stress NSAIDs are already known for, so these effects compound.

Proton Pump Inhibitors

Acid-suppressing drugs like omeprazole, lansoprazole, and pantoprazole are among the most prescribed medications globally, and their link to hyponatremia is real but less dramatic than the classes above. A large population-based case-control study found that people who had used a proton pump inhibitor for at least 30 days before hospital admission were significantly more likely to have hyponatremia than those who had not, with about a 60 percent higher odds.⁹

A postmarketing safety analysis of adverse drug reports found that hyponatremia was the least pronounced electrolyte disturbance linked to PPIs but still reached statistical significance for omeprazole, lansoprazole, and rabeprazole. Reports involving esomeprazole and pantoprazole did not reach significance in that dataset.¹⁰ Case reports have documented severe hyponatremia from pantoprazole specifically, including in an elderly patient who developed serious symptoms and took two months to recover normal sodium levels after stopping the drug.¹¹ The exact mechanism is not well established, but the association is something to keep in mind, especially for older adults on long-term PPI therapy.

Antipsychotics

Antipsychotic medications can lower sodium through a less intuitive route: excessive thirst. Older first-generation antipsychotics like haloperidol have been strongly associated with polydipsia, a compulsion to drink large quantities of water. One cross-sectional study found the prevalence of hyponatremia to be about 26 percent with first-generation antipsychotics compared to roughly 5 percent with second-generation agents.⁴ Drugs with high affinity for dopamine receptors appear to carry higher risk for triggering polydipsia, while clozapine may actually help reduce compulsive water drinking in affected patients. The mechanism is thought to involve disruption of thirst regulation in the brain rather than a direct effect on the kidney, which makes it a different beast from thiazide- or SSRI-driven hyponatremia.

Chemotherapy Agents and Cancer Drugs

Several chemotherapy drugs are linked to low sodium. Cisplatin, one of the most widely used platinum-based agents, can cause hyponatremia through at least two pathways: it stimulates ADH secretion, and it can directly damage the kidney tubules responsible for sodium reabsorption.¹² Vincristine, cyclophosphamide, and some targeted therapies have also been implicated. Because cancer patients are often already dealing with nausea, poor nutrition, and fluid balance challenges, drug-induced drops in sodium can be harder to spot and more dangerous.

Immune checkpoint inhibitors, a newer class of cancer immunotherapy drugs including nivolumab, pembrolizumab, and ipilimumab, cause hyponatremia through yet another route. These drugs can trigger autoimmune inflammation of the pituitary gland, leading to secondary adrenal insufficiency and, in turn, low sodium. In one study, the average time from starting an immune checkpoint inhibitor to being diagnosed with adrenal-insufficiency-driven hyponatremia was about 164 days.¹³ Because the problem is hormonal rather than renal, it requires a different treatment approach: replacing the missing cortisol rather than restricting fluid.

Synthetic Hormones

Desmopressin is a synthetic version of ADH prescribed for conditions like diabetes insipidus and bedwetting. It binds selectively to the receptor that tells the kidney to hold onto water, and it does so with a longer duration of action than the body’s natural hormone. That makes it effective for its intended purpose but also capable of causing significant hyponatremia in susceptible patients who retain too much water.¹⁴

Oxytocin, used to induce labor and manage postpartum bleeding, is a less obvious culprit. At the doses used clinically, oxytocin can act as an antidiuretic by stimulating the same kidney receptor that ADH uses. Animal studies and human data have confirmed that pharmacological doses of oxytocin increase water reabsorption in the kidney’s collecting ducts.¹⁴ This risk is compounded by the fact that oxytocin is often administered with intravenous fluids during labor, which can further dilute sodium. Severe hyponatremia in obstetric settings, while uncommon, has been well documented.

MDMA and Recreational Drugs

MDMA (ecstasy) has been responsible for deaths from acute hyponatremia, and the mechanism is a perfect storm of contributing factors. The drug triggers serotonin-mediated release of ADH from the pituitary gland, which tells the kidneys to retain water.¹⁵ At the same time, users at dance events or raves often drink large amounts of water to counteract hyperthermia and dehydration from hours of physical activity in hot environments. The combination of excessive water intake, sodium loss through sweating, and inappropriate ADH release can produce a catastrophic drop in sodium that leads to brain swelling.¹⁶

Young women appear to be at particular risk for MDMA-associated hyponatremia, possibly because estrogen enhances ADH’s effects on the kidney. The harm-reduction message is counterintuitive: while staying hydrated during physical activity is normally good advice, drinking water aggressively while on MDMA can be lethal. Sipping small amounts and replacing electrolytes rather than guzzling plain water is the safer approach.

When Drugs Combine

Taking two or more hyponatremia-causing medications at the same time does not just add risk, it can multiply it. The most studied combination is a thiazide diuretic plus an SSRI. Case reports first flagged this pairing as particularly dangerous, highlighting a possible synergistic impairment of the kidney’s ability to excrete free water.¹⁷ Larger studies have since confirmed the association. Among patients taking thiazides alone, about 10 percent developed hyponatremia; among those on SSRIs alone, about 9 percent did. But patients on both had a prevalence of roughly 13 percent, and the adjusted odds of hyponatremia were about 25 percent higher with the combination than with either drug alone.¹⁸

A review of antidepressant-related hyponatremia found that concurrent use of thiazide diuretics increased the odds by a factor of roughly 11 to 13.⁴ This matters because the combination is extremely common: many older adults take a blood pressure pill and an antidepressant simultaneously. Adding an NSAID for joint pain on top of that further raises the risk by removing the prostaglandin brake on ADH. When your medication list contains two or three drugs that each independently nudge sodium downward, the cumulative effect can be clinically serious even when no single drug alone would have caused trouble.

Who Faces the Greatest Risk

Drug-induced hyponatremia is not an equal-opportunity problem. Several factors make certain people far more vulnerable:

Age: Older adults are disproportionately affected because the aging kidney is less efficient at handling water loads, ADH regulation becomes less precise, and older people are more likely to be on multiple medications.
Sex: Women face higher risk, particularly for thiazide-induced hyponatremia. One study found that female sex was associated with more than four times the odds of developing low sodium on a thiazide.¹⁹
Low body weight: Lower BMI was an independent predictor for thiazide-induced hyponatremia in the same study, possibly because smaller people have less total body water to buffer a dilution effect.
Underlying conditions: Heart failure, liver cirrhosis, and kidney disease all independently predispose to hyponatremia, and adding a drug that pushes sodium down further compounds an already precarious balance.

The timing after starting a new medication is also critical. For most drug classes, the risk is concentrated in the first weeks of treatment. This pattern is consistent across SSRIs, antipsychotics, anticonvulsants, and PPIs. For thiazides specifically, the highest danger zone is the first few weeks, with risk settling to a lower plateau after roughly three months. Checking a basic blood panel within one to two weeks of starting any high-risk drug is a practical safety measure that is underused in routine clinical practice.

Genetic Susceptibility

Not everyone on a thiazide or an SSRI develops hyponatremia, and genetics appears to be part of the explanation. A study examining both clinical and genetic risk factors for thiazide-induced hyponatremia identified a specific genetic variant in a gene called KCNJ1 that was independently associated with roughly six-fold higher odds of developing the condition.¹⁹ KCNJ1 encodes a potassium channel involved in kidney electrolyte handling, so variants in this gene plausibly alter how the kidney responds to thiazide-induced changes in sodium and water balance.

A separate genome-wide analysis identified additional genetic regions linked to thiazide-induced hyponatremia, including a variant in a gene called SLCO2A1 that encodes a prostaglandin transporter active in the part of the kidney where thiazides work.²⁰ This finding is especially interesting because it ties back to the prostaglandin pathway that NSAIDs also disrupt, suggesting that some people may have a genetically thinner safety margin for maintaining sodium balance under pharmacological stress. This area of research is still early, and genetic testing for hyponatremia risk is not yet part of clinical practice, but it helps explain why one person tolerates a drug without issues while another ends up hospitalized.

The Danger of Correcting Too Fast

One of the more treacherous aspects of drug-induced hyponatremia is that the treatment itself can cause serious harm if done improperly. When sodium levels have been low for more than a day or two, the brain adapts by shedding solutes from its cells to prevent swelling. If sodium is then corrected too quickly, water rushes out of brain cells faster than they can readjust, leading to a condition called osmotic demyelination syndrome. This involves breakdown of the blood-brain barrier, damage to the protective insulation around nerve fibers, and potentially severe, irreversible neurological injury.²¹

For drug-induced cases, the first step in management is usually stopping or replacing the offending medication, combined with fluid restriction. Sodium correction rates are carefully controlled, typically aiming for no more than a modest increase over 24 hours. Patients with liver disease, alcohol use disorder, or severe malnutrition are at especially high risk for osmotic demyelination, and management in these populations requires extra caution. The takeaway for anyone monitoring their own health: if you develop symptoms like confusion, headache, nausea, or muscle cramps while on a medication known to affect sodium, getting a blood test is important, but rapid “fixes” like drinking salt water or drastically changing your fluid intake on your own are not safe without medical guidance.

Drugs That May Actually Protect Against Low Sodium

An interesting wrinkle in this landscape is that some medications appear to lower hyponatremia risk rather than raise it. Loop diuretics like furosemide, despite being in the same broad family as thiazides, act on a kidney segment that does not impair the diluting mechanism. Lithium, commonly used for bipolar disorder, causes a form of kidney resistance to ADH that, while it creates its own set of problems, works against the water retention that drives most drug-induced hyponatremia. SGLT2 inhibitors, the diabetes drugs that include empagliflozin and dapagliflozin, promote water and glucose loss through urine in a way that tends to concentrate rather than dilute sodium. These drugs have been gaining attention for their potential protective role, and some clinicians consider them a useful option when a patient needs a new medication but already has risk factors for low sodium.

1
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3
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PubMed Central. Syndrome of inappropriate antidiuretic hormone secretion associated with prolonged keterolac use
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PubMed. Nonsteroidal anti-inflammatory drug-induced severe hyponatremia
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PubMed Central. Association of proton pump inhibitor use and significant hyponatremia-a US population-based case-control study
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PubMed Central. Pantoprazole-related Symptomatic Hyponatremia
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PubMed Central. Risk Factors for Anticancer Drug-Induced Hyponatremia: An Analysis Using the Japanese Adverse Drug Report (JADER) Database
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Nephrology Dialysis Transplantation. Hyponatremia and other electrolyte abnormalities in patients receiving immune checkpoint inhibitors
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The American Journal of the Medical Sciences. Hyponatremia Associated with 3,4-Methylenedioxymethylamphetamine (“Ecstasy”) Abuse
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PubMed Central. Rare but relevant: MDMA and hyponatraemia
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PubMed. Severe hyponatremia associated with the combined use of thiazide diuretics and selective serotonin reuptake inhibitors
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PubMed Central. Evaluation of hyponatremia among older adults exposed to selective serotonin reuptake inhibitors and thiazide diuretics
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PubMed Central. Osmotic Demyelination Syndrome Following Rapid Correction of Hyponatremia in a Young Woman: A Case Report and Review of Literature