A client is prescribed lithium carbonate tablets PO at a dose of 900 mg/day divided into three doses. Each tablet contains 300 mg. How many tablets should the client take per dose?

Choice A reason: Taking 2 tablets per dose would result in a single dose of 600 mg. Over three daily administrations, this would total 1800 mg per day. This dosage significantly exceeds the prescribed 900 mg/day limit and would likely lead to acute lithium toxicity and severe physiological distress for the patient. Choice B reason: Taking 3 tablets per dose would equal 900 mg for a single administration. If repeated three times daily as instructed by the "divided into three doses" order, the patient would receive 2700 mg total, which is a dangerous overdose that violates the prescribed pharmacological parameters for this medication. Choice C reason: Taking 4 tablets per dose would equate to 1200 mg per administration. Over the course of a full day with three doses, the cumulative intake would be 3600 mg. This amount is clinically contraindicated and could result in lethal serum concentrations of lithium carbonate, causing multisystem organ failure. Choice D reason: To calculate the dose, the total daily amount of 900 mg is divided by 3 doses, resulting in 300 mg per dose. Since each available tablet is 300 mg, the formula (Dose Ordered / Dose on Hand = Amount to Administer) shows that 300 mg / 300 mg = 1 tablet.