From the FDA Drug Label
Chronic lithium therapy may be associated with diminution of renal concentrating ability, occasionally presenting as nephrogenic diabetes insipidus, with polyuria and polydipsia Such patients should be carefully managed to avoid dehydration with resulting lithium retention and toxicity. Lithium toxicity is closely related to serum lithium levels, and can occur at doses close to therapeutic levels CONTRAINDICATIONS Lithium should generally not be given to patients with significant renal or cardiovascular disease, severe debilitation or dehydration, or sodium depletion, and to patients receiving diuretics, since the risk of lithium toxicity is very high in such patients.
The patient, RS, is likely to have a high lithium level due to dehydration, as stated in the drug label that dehydration can lead to lithium retention and toxicity 1 and that lithium should not be given to patients with severe dehydration since the risk of lithium toxicity is very high in such patients 1.
From the Research
I would anticipate that RS's lithium level would increase significantly after becoming dehydrated. Dehydration reduces the body's total water content, which leads to a higher concentration of lithium in the blood as the same amount of medication is now dissolved in less fluid. This is particularly dangerous because lithium has a narrow therapeutic window, meaning the difference between therapeutic and toxic levels is small. When a patient on lithium becomes dehydrated, their serum lithium concentration can rise into the toxic range (above 1.2 mEq/L), even if they haven't changed their medication dosage. This can lead to lithium toxicity symptoms including tremor, confusion, lethargy, slurred speech, muscle weakness, and in severe cases, seizures or coma. The kidneys play a crucial role in lithium clearance, and dehydration impairs renal function, further contributing to lithium retention, as discussed in a study on lithium nephrotoxicity 2. Patients taking lithium should be advised to maintain adequate hydration at all times, especially during hot weather, exercise, or illness involving fever, vomiting, or diarrhea. If RS is dehydrated, immediate rehydration is necessary, and lithium levels should be checked promptly. Depending on the severity of dehydration and symptoms, temporary dose reduction or discontinuation of lithium might be required until fluid balance is restored. A recent case report highlights the importance of monitoring lithium levels in patients with COVID-19, but in this case, dehydration is the primary concern 3.
Some key points to consider in this scenario include:
- Dehydration can lead to increased lithium levels due to decreased renal function and reduced water content in the body.
- Lithium has a narrow therapeutic window, making it essential to monitor levels closely, especially in situations that may affect hydration status.
- Patients on lithium should be educated on the importance of maintaining adequate hydration, particularly in hot weather or during physical activity.
- Immediate rehydration and monitoring of lithium levels are crucial in cases of suspected dehydration in patients taking lithium.
In terms of the potential effects of dehydration on lithium levels, it is essential to consider the mechanisms by which lithium is cleared from the body and how dehydration can impact these processes. As noted in a study on lithium intoxication, dehydration can lead to impaired renal function, which can further contribute to lithium retention 4. Additionally, a case report on lithium toxicity highlights the importance of monitoring lithium levels in patients who may be at risk of dehydration 5.
Overall, the most critical consideration in this scenario is the potential for dehydration to lead to increased lithium levels, which can have severe consequences for the patient's health. Therefore, it is essential to prioritize immediate rehydration and monitoring of lithium levels in this patient.