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 lithium at the same dose of 700mg daily, as the patient's lithium level of 0.57 mEq/L is within the therapeutic range (0.5-1.2 mEq/L) despite missing two doses due to vomiting. The patient should resume their regular dosing schedule immediately, ensuring they take the medication with food to minimize gastrointestinal irritation, as suggested by clinical expertise 1. Adequate hydration should be maintained to prevent lithium toxicity, which is closely related to serum lithium concentrations and can occur at doses close to therapeutic concentrations 1. If vomiting persists, the patient should contact their healthcare provider, as continued vomiting may lead to dehydration and potentially dangerous increases in lithium levels.

Key Considerations

• The patient should be monitored for signs of lithium toxicity, such as tremor, confusion, lethargy, or diarrhea, which were reported as common adverse effects in a study on lithium treatment for Kleine-Levin syndrome 1.
• Lithium has a narrow therapeutic window, but since the current level is in the lower therapeutic range, it's safe to resume the previous dose without titration, considering the medication's pharmacokinetics and the patient's clinical state.
• The missed doses likely caused only a minor decrease in serum concentration given lithium's half-life of approximately 24 hours, and the body will re-establish steady-state levels within 4-5 days of consistent dosing.
• Regular monitoring of the patient’s clinical state and of serum lithium concentrations is necessary, with serum concentrations determined twice per week during the acute phase and until the serum concentrations and clinical condition of the patient have been stabilized, as recommended for patients with Kleine-Levin syndrome 1.

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
• Patients with polyuria and impaired urinary concentrating ability are at increased risk of acute lithium toxicity because of excessive renal losses of fluid, and these symptoms should be treated in the first instance with dosage reduction 5
• Lithium intoxication can affect multiple organs, and clinical manifestations vary from asymptomatic supratherapeutic drug concentrations to clinical toxicity such as confusion, ataxia, or seizures 4