What is the treatment for lithium-induced polydipsia?

Treatment for Lithium-Induced Polydipsia

The primary treatment for lithium-induced polydipsia is to ensure ad libitum access to fluids while considering thiazide diuretics for severe cases, but medication adjustment may be necessary in patients with nephrogenic diabetes insipidus (NDI). 1, 2

Understanding Lithium-Induced Polydipsia

Lithium-induced polydipsia is commonly associated with nephrogenic diabetes insipidus (NDI), a condition where the kidneys become resistant to the effects of antidiuretic hormone (vasopressin), resulting in:

• Excessive thirst (polydipsia)
• Excessive urination (polyuria)
• Inability to concentrate urine

This condition is specifically listed in guidelines as a distinguishing characteristic of acquired NDI 1. The FDA drug label for lithium explicitly warns that "chronic lithium therapy may be associated with diminution of renal concentrating ability, occasionally presenting as nephrogenic diabetes insipidus, with polyuria and polydipsia" 2.

Treatment Algorithm

1. Ensure adequate fluid access

   • Provide ad libitum (free) access to fluids to prevent dehydration, hypernatraemia, and other complications 1
   • For patients who can self-regulate, allow them to follow their thirst sensation
   • For patients unable to self-regulate (infants, cognitively impaired), offer water frequently

2. Consider medication adjustment

   • If clinically appropriate, consider reducing lithium dose or switching to an alternative mood stabilizer
   • Lithium levels should be monitored closely (every 2-3 months during maintenance phase) 3
   • Target serum lithium levels at the lower effective range (0.6-0.8 mmol/L) 3

3. For severe cases resistant to above measures:

   • Thiazide diuretics may be effective in reducing polyuria 4
   • IMPORTANT CAUTION: Before starting diuretics, lithium dose must be reduced to prevent lithium toxicity due to volume depletion and reduced renal lithium clearance 4

4. Monitor for complications

   • Regular monitoring of renal function, including urinalysis and tests to evaluate tubular function 2
   • Watch for progressive or sudden changes in renal function, even within normal range 2
   • Monitor serum sodium levels to prevent dangerous fluctuations

Special Considerations

• Avoid NSAIDs when possible: While some research suggests indomethacin may have antidiuretic effects in lithium-induced NDI 5, the safety of such therapy requires further study and carries risks of drug interactions.

• Risk of dehydration: Patients with lithium-induced polydipsia/NDI are at serious risk if they cannot access fluids freely. This condition can become life-threatening when free access to water is impossible 4.

• Vasopressin resistance: Unlike central diabetes insipidus, lithium-induced NDI is typically resistant to vasopressin (desmopressin/DDAVP) therapy 6, making fluid management the cornerstone of treatment.

• Monitoring during procedures: If patients need to fast for procedures (>4 hours), intravenous fluid administration (5% dextrose in water) should be provided at maintenance rates 1.

Pitfalls to Avoid

1. Do not restrict fluids - This can lead to dangerous dehydration and hypernatremia

2. Do not start thiazide diuretics without first reducing lithium dose - This can precipitate lithium toxicity 4

3. Do not assume desmopressin (DDAVP) will be effective - Lithium-induced NDI is typically resistant to vasopressin therapy 6

4. Do not overlook the possibility of coexisting psychogenic polydipsia - Some patients may have both conditions, leading to wide swings in serum sodium 7

5. Do not fail to monitor patients during situations where fluid access is limited - This includes medical procedures, hospitalizations, or other situations where the patient cannot freely drink water 4