A prescription orders 300 mg of carbamazepine, but only 200 mg tablets are available. How many tablets should be dispensed?

To determine how many tablets should be dispensed for a prescription of 300 mg of carbamazepine using 200 mg tablets, one must calculate the total number of tablets required to meet the prescribed dosage.

In this case, the total required dosage is 300 mg. Since each tablet contains 200 mg, you can divide the total amount needed by the amount per tablet:

300 mg (required) ÷ 200 mg (per tablet) = 1.5 tablets.

This calculation demonstrates that 1.5 tablets are necessary to achieve the prescribed dosage. Dispensing 1 tablet would only provide 200 mg, which is insufficient. Conversely, dispensing 2 tablets would result in 400 mg, exceeding the prescribed amount.

Therefore, the correct quantity to dispense in this situation is indeed 1.5 tablets, aligning with the laboratory standard for doses that cannot be rounded down or up when exact dosing is critical. In real-world practice, it is common for pharmacists to either provide the exact number of tablets (if allowed) or to consult with the prescribing physician for further instructions on how to best facilitate the dosing when exact fractions are involved.