How to recommence lithium (lithium carbonate) therapy in a patient with a subtherapeutic lithium level of 0.57 mEq/L, who missed two doses due to vomiting, while on a regimen of 700mg of lithium (lithium carbonate)?

From the Guidelines

I strongly recommend restarting the lithium at the same dose of 700mg daily, as the patient's lithium level of 0.57 mEq/L is subtherapeutic, and resuming the regular dosing schedule is crucial to achieve therapeutic levels and prevent breakthrough mood symptoms. The patient should resume their regular dosing schedule immediately, ensuring they take the medication with food to minimize gastrointestinal upset. Although the provided study 1 discusses the use of lithium for Kleine-Levin syndrome, its general guidance on lithium therapy, including the importance of monitoring serum lithium concentrations and maintaining adequate hydration, is relevant to this patient's situation.

Key Considerations

• The patient's lithium level is currently subtherapeutic at 0.57 mEq/L, indicating the need to resume the medication as soon as possible to prevent worsening of symptoms.
• The patient should be advised to maintain adequate hydration, aiming for 2-3 liters of fluid daily, to prevent lithium toxicity, as lithium levels can be affected by fluid status 1.
• If vomiting persists for more than 24 hours, the patient should contact their healthcare provider, as continued fluid loss may affect lithium levels and increase the risk of toxicity.
• A follow-up lithium level should be checked in about 5-7 days to ensure it remains therapeutic and to adjust the dose if necessary, considering the narrow therapeutic window of lithium.

Monitoring and Adjustments

• Regular monitoring of the patient’s clinical state and serum lithium concentrations is necessary, as recommended by the study 1, to ensure the balance between desirable and undesirable effects is maintained.
• The study 1 suggests that serum concentrations should be determined twice per week during the acute phase and until the serum concentrations and clinical condition of the patient have been stabilized, which may guide the frequency of monitoring in this patient.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Acute Mania: Optimal patient response to lithium carbonate usually can be established and maintained with 600 mg t.i.d.. Such doses will normally produce an effective serum lithium level ranging between 1 and 1. 5 mEq/L. Dosage must be individualized according to serum levels and clinical response. Long-term Control: The desirable serum lithium levels are 0. 6 to 1.2 mEq/l. Dosage will vary from one individual to another, but usually 300 mg of lithium carbonate t.i.d. or q.i.d., will maintain this level.

To recommence lithium therapy in a patient with a subtherapeutic lithium level of 0.57 mEq/L, who missed two doses due to vomiting, while on a regimen of 700mg of lithium (lithium carbonate), resume the previous dose of 700mg. The patient's serum level is slightly below the desirable range of 0.6 to 1.2 mEq/L, but since the patient missed two doses, it is likely that the level will increase once the medication is restarted. Monitor the patient's serum lithium level and clinical response closely to determine if any adjustments to the dose are needed 2.

• Key considerations:
  • The patient's current serum level is close to the lower end of the desirable range.
  • The patient missed two doses, which likely contributed to the subtherapeutic level.
  • Close monitoring of the patient's serum level and clinical response is necessary to ensure the patient's safety and the effectiveness of the treatment.

From the Research

Recommencing Lithium Therapy

To recommence lithium therapy in a patient with a subtherapeutic lithium level of 0.57 mEq/L, who missed two doses due to vomiting, while on a regimen of 700mg of lithium (lithium carbonate), consider the following:

• The patient's current lithium level is below the therapeutic range of 0.6-0.8 mmol/L 3
• The patient missed two doses due to vomiting, which may have contributed to the subtherapeutic level
• The usual maintenance daily dose is 25-35 mmol (lithium carbonate 925-1300 mg) for patients aged <40 years; 20-25 mmol (740-925 mg) for those aged 40-60 years; and 15-20 mmol (550-740 mg) for patients aged >60 years 3

Adjusting Lithium Dosage

When adjusting the lithium dosage, consider the following:

• Lithium dosages should be adjusted on the basis of the serum concentration drawn (optimally) 12 hours after the last dose 3
• The efficacy of lithium is clearly dose-dependent and reliably correlates with serum concentrations 3
• It is generally accepted that concentrations should be maintained between 0.6 and 0.8 mmol/L, although some authors still favour 0.8-1.2 mmol/L 3

Monitoring and Precautions

When recommencing lithium therapy, consider the following:

• Careful attention to dosing, monitoring, and titration is required due to lithium's narrow therapeutic index and the influence of kidney function 4
• Lithium clearance is considered to decrease with aging, and renal insufficiency is associated with a considerable reduction in renal clearance of lithium 3
• Patients with polyuria and impaired urinary concentrating ability are at increased risk of acute lithium toxicity due to excessive renal losses of fluid 5