A nurse needs to administer haloperidol IM at a dose of 5 mg. The medication available is haloperidol injection 10 mg/mL. How many mL should the nurse administer?

Choice A reason: To calculate the correct volume, the nurse uses the standard formula: Desired dose (5 mg) divided by the dose on hand (10 mg) multiplied by the volume (1 mL). Therefore, 5 divided by 10 equals 0.5. Administering 0.5 mL provides exactly the 5 mg prescribed. Choice B reason: Administering 2 mL would result in the patient receiving 20 mg of haloperidol. This is four times the prescribed dose and could lead to severe extrapyramidal side effects, acute dystonia, or neuroleptic malignant syndrome, representing a significant and dangerous medication administration error by the nurse. Choice C reason: A volume of 0.25 mL would only deliver 2.5 mg of the medication. This sub-therapeutic dose would likely be ineffective in managing the patient's acute psychiatric symptoms or agitation, failing to meet the clinical objectives established by the prescribing healthcare provider's original medication order. Choice D reason: Administering 1 mL would deliver 10 mg of haloperidol, which is double the intended 5 mg dose. Overdosing a patient on high-potency antipsychotics increases the risk of cardiac complications, such as QTc prolongation, and requires immediate reporting and monitoring for adverse neurological reactions.