A patient with schizophrenia has been prescribed haloperidol 10 mg IM. The vial available contains haloperidol 5 mg/mL. How many mL should the nurse administer?

Choice A reason: 3 mL contains 15 mg, which exceeds the prescribed dose by 5 mg. This would risk overdose and adverse effects such as extrapyramidal symptoms. Choice B reason: 2 mL contains exactly 10 mg, matching the prescribed dose. This ensures accurate and safe administration. Step 1: Ordered dose = 10 mg. Step 2: Concentration = 5 mg per 1 mL. Step 3: (10 mg ÷ 5 mg) = 2 mL. Result = 2 mL. Choice C reason: 1 mL contains only 5 mg, which is half the prescribed dose. Administering this amount would underdose the patient. Choice D reason: 4 mL contains 20 mg, which is double the prescribed dose. This would cause toxicity and severe side effects.