A patient on lithium therapy requires a dose of 600 mg per day divided into two doses using available tablets of 300 mg each. How should the nurse plan the administration?

Choice A reason: Administering 3 tablets per dose twice a day would result in a total daily dose of 1,800 mg (900 mg per dose). This significantly exceeds the 600 mg daily prescription and would likely lead to acute lithium toxicity, characterized by severe tremors, ataxia, and potential renal failure. Choice B reason: This plan provides 600 mg in a single administration. While the total daily amount is correct, the order specifically requires the dose to be divided into two administrations. Dividing the dose helps maintain steady-state serum levels and minimizes peak-dose side effects associated with high single-dose lithium concentrations. Choice C reason: The total daily dose is 600 mg. To divide this into two equal doses, 300 mg must be given at each interval. Since each tablet contains 300 mg, administering 1 tablet in the morning and 1 tablet in the evening accurately fulfills the physician's pharmacological order for the patient. Choice D reason: A half tablet would provide only 150 mg per dose, totaling 300 mg per day. This is only half of the required 600 mg daily dose. Subtherapeutic lithium levels are ineffective for stabilizing mood in bipolar disorder and increase the risk of the patient experiencing a manic episode.