23. The label reads 400 mcg per \( \mathrm{mL} ; 0.6 \mathrm{mg} \) has been ordered.

1. Convert the label concentration to the same unit as the ordered dose. The label reads \(400 \, \mu\text{g/mL}\). Since \(1 \, \text{mg} = 1000 \, \mu\text{g}\), we have: \[ 400 \, \mu\text{g/mL} = \frac{400}{1000} \, \text{mg/mL} = 0.4 \, \text{mg/mL}. \] 2. The dosage ordered is \(0.6 \, \text{mg}\). To find the required volume in mL to obtain \(0.6 \, \text{mg}\) with a concentration of \(0.4 \, \text{mg/mL}\), use the formula: \[ \text{Volume (mL)} = \frac{\text{Dose (mg)}}{\text{Concentration (mg/mL)}}. \] 3. Substitute the known values: \[ \text{Volume (mL)} = \frac{0.6 \, \text{mg}}{0.4 \, \text{mg/mL}} = 1.5 \, \text{mL}. \] Thus, \(1.5 \, \text{mL}\) of the solution should be administered.