From the FDA Drug Label
Caution should be used when lithium and diuretics or angiotensin converting enzyme (ACE) inhibitors are used concomitantly because sodium loss may reduce the renal clearance of lithium and increase serum lithium levels with risk of lithium toxicity. The patient's symptom is most likely the result of a drug-drug interaction between lithium carbonate and hydrochlorothiazide 1.
- Key points:
- Hydrochlorothiazide is a diuretic
- Diuretics can increase serum lithium levels by reducing renal clearance of lithium
- Elevated serum lithium levels can cause symptoms such as coarse tremor of the upper extremities.
From the Research
The most likely medication causing a drug-drug interaction with lithium carbonate in a patient presenting with coarse tremor and elevated lithium levels is a thiazide diuretic such as hydrochlorothiazide. This is because thiazide diuretics significantly reduce lithium clearance by promoting sodium depletion, which leads to increased reabsorption of lithium in the proximal tubules of the kidneys, as noted in various studies 2, 3, 4, 5, 6. The interaction between lithium and thiazide diuretics can raise lithium levels by 25-40% within days of starting the diuretic, potentially causing lithium toxicity. Key points to consider in this scenario include:
- The coarse tremor of the upper extremities is a classic sign of lithium toxicity, along with other symptoms like confusion, ataxia, and gastrointestinal disturbances.
- Other medications that commonly interact with lithium include NSAIDs (like ibuprofen), ACE inhibitors, and loop diuretics, but thiazides typically cause the most pronounced effect.
- Management should include immediate discontinuation of the thiazide diuretic, temporary reduction or interruption of lithium dosing, monitoring of serum lithium levels, and adequate hydration to enhance lithium excretion.
- If a diuretic is necessary, potassium-sparing diuretics like amiloride have less effect on lithium levels and may be safer alternatives. It's also important to note that while other studies discuss various aspects of lithium treatment and tremor diagnosis 2, 3, 5, 6, the most critical factor in this patient's case is the interaction between lithium and thiazide diuretics, as highlighted by the elevated lithium levels and coarse tremor. Given the potential for severe complications from lithium toxicity, prioritizing the management of this interaction is crucial for the patient's morbidity, mortality, and quality of life outcomes.