What Is Lithium Toxicity?
Lithium toxicity occurs when the concentration of lithium in the blood becomes dangerously high. Lithium salts are commonly prescribed to manage bipolar disorder, but the therapeutic window is narrow. Even a small increase in dosage may push blood levels into a toxic range. Toxicity can develop over time with chronic use, or quickly after an accidental or intentional overdose.
Causes and Risk Factors
The most common causes of lithium toxicity include a change in kidney function, dehydration, drug interactions, and excessive intake. Because lithium is excreted through the kidneys, any condition that reduces renal blood flow or glomerular filtration can lead to accumulation. Risk factors include:
- Advanced age
- Chronic kidney disease
- Heart failure
- Use of diuretics or nonsteroidal anti-inflammatory drugs
- Low salt intake
- Dehydration from vomiting, diarrhea, or fever
Symptoms of Lithium Toxicity
Symptoms range from mild to life-threatening and depend on the blood lithium level and how quickly it rises. Early signs often include nausea, vomiting, diarrhea, tremor, and fatigue. As toxicity worsens, neurological effects become prominent. These may include:
- Confusion and agitation
- Slurred speech and dizziness
- Muscle twitching or weakness
- Ataxia (loss of coordination)
- Seizures
- Coma
Chronic toxicity can also affect other organs. Long-term elevated lithium levels may impair renal function, leading to nephrogenic diabetes insipidus with excessive thirst and urination. Thyroid dysfunction, particularly hypothyroidism, is another possible consequence.
Diagnosis
Diagnosis is based on clinical signs and a blood test that measures the lithium concentration. The therapeutic range is generally considered to be between 0.6 and 1.2 mmol/L, although the range may vary. Levels above 1.5 mmol/L are usually considered toxic, and levels above 2.5 mmol/L are often severe. However, some patients show symptoms at lower levels, especially if they are older. Blood tests may also assess kidney function, electrolyte balance, and thyroid status. An electrocardiogram is sometimes needed to check for cardiac effects.
Treatment of Lithium Toxicity
Treatment depends on the severity. In mild cases, stopping the medication and ensuring adequate hydration may be sufficient. For moderate toxicity, supportive care in a hospital is necessary. This can include intravenous fluids and monitoring of vital signs and neurological status. In severe cases, hemodialysis is the most effective way to remove lithium from the body. Hemodialysis is generally recommended for patients with high blood lithium levels, significant neurological impairment, or kidney failure. Treatment also addresses any underlying causes, such as correcting dehydration or adjusting other medications.
Prevention
Preventing lithium toxicity involves regular monitoring and patient education. Prescribers should periodically check blood lithium levels and renal function, especially after any change in dose or the addition of new medications. Patients must be reminded to maintain a stable salt and fluid intake and to seek medical advice if they become dehydrated. Education about the early symptoms of toxicity is essential so that prompt treatment can be sought. For those at risk, a medication review can help identify interactions that might raise lithium levels.
When to Seek Emergency Help
Lithium toxicity is a medical emergency. Severe symptoms such as confusion, severe tremor, seizures, or decreased consciousness require immediate hospital care. Delayed treatment can result in permanent neurological damage or death. If an overdose is suspected, do not delay. Contact emergency services or go to the nearest emergency department right away.
Outlook
Outcome depends on the severity and promptness of treatment. With early recognition and appropriate care, most individuals recover fully. However, long-term kidney and thyroid issues may require ongoing management. Anyone taking lithium should work closely with a healthcare professional to balance the benefits of treatment against the risks of toxicity.