DOSAGE AND ADMINISTRATION
Doses of extended-release tablets are usually given b.i.d. (approximately 12-hour intervals). When initiating therapy with extended-release lithium, dosage must be individualized according to serum levels and clinical response.
When switching a patient from immediate-release capsules to the lithium carbonate extended-release tablets, give the same total daily dose when possible. Most patients on maintenance therapy are stabilized on 900 mg daily, e.g., 450 mg lithium carbonate extended-release b.i.d. When the previous dosage of immediate-release lithium is not a multiple of 450 mg, for example, 1500 mg, initiate lithium extended-release tablet at the multiple of 450 mg nearest to, but below, the original daily dosage, i.e., 1350 mg. When the two doses are unequal, give the larger dose in the evening. In the above example, with a total daily dosage of 1350 mg, generally 450 mg lithium carbonate extended-release should be given in the morning and 900 mg lithium carbonate extended-release in the evening. If desired, the total daily dosage of 1350 mg can be given in three equal 450 mg lithium carbonate extended-release doses. These patients should be monitored at 1 to 2 week intervals, and dosage adjusted if necessary, until stable and satisfactory serum levels and clinical state are achieved.
When patients require closer titration than that available with doses of lithium carbonate extended-release in increments of 450 mg, immediate-release capsules should be used.
Acute Mania - Optimal patient response to lithium carbonate can usually be established and maintained with 1800 mg per day in divided doses. Such doses will normally produce the desired serum lithium level ranging between 1 and 1.5 mEq/L.
Dosage must be individualized according to serum levels and clinical response. Regular monitoring of the patient's clinical state and serum lithium levels is necessary. Serum levels should be determined twice per week during the acute phase, and until the serum level and clinical condition of the patient have been stabilized.
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 900 mg to 1200 mg per day in divided doses will maintain this level. Serum lithium levels in uncomplicated cases receiving maintenance therapy during remission should be monitored at least every two months.
Patients unusually sensitive to lithium may exhibit toxic signs at serum levels below 1 mEq/L.
N.B. - Blood samples for serum lithium determinations should be drawn immediately prior to the next dose when lithium concentrations are relatively stable (i.e., 8 to 12 hours after the previous dose). Total reliance must not be placed on serum levels alone. Accurate patient evaluation requires both clinical and laboratory analysis.
Elderly patients often respond to reduced dosage, and may exhibit signs of toxicity at serum levels ordinarily tolerated by younger patients.
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