If a patient requires haloperidol IM and has a solution of 5 mg/mL, how would that ratio be set for calculating the administration of 3 mg?

The correct approach to set the ratio for calculating the administration of 3 mg of haloperidol from a solution of 5 mg/mL is established in the first option. The expression 5 mg/1 mL = 3 mg/X mL represents a proportion where the concentration of the solution is compared to the desired dosage.

In this case, we know there is 5 mg of haloperidol available in 1 mL of the solution. To find out how many milliliters (X) will provide the desired dose of 3 mg, we use the ratio that equates what's available (5 mg in 1 mL) to what is needed (3 mg in X mL). By cross-multiplying and solving for X, we can accurately determine the volume required to administer the correct dosage.

The other choices do not correctly represent the relationship between the concentration of the drug and the desired dosage. They either set the ratios incorrectly or reverse the relationship, which would lead to confusion and incorrect calculations when determining the proper volume to administer to the patient.