A client is receiving ketorolac IM 45 mg IM every 6 hours for postoperative pain. The available 2 mL vial is labeled, ketorolac IM 30 mg/mL. How many mL. should the nurse administer? (Enter numerical value only. If rounding is required, round to the nearest tenth)

To determine the volume to administer, use the standard dose calculation formula: desired dose divided by dose on hand, multiplied by volume on hand. The desired dose is 45 mg, the concentration is 30 mg per mL, and the volume per mL is 1 mL. Calculation: 45 mg ÷ 30 mg/mL = 1.5 mL. This result is confirmed by dimensional analysis: 45 mg × (1 mL / 30 mg) = 1.5 mL. The keyed answer of 1.5 mL is therefore correct. A common student error is inverting the ratio, which would yield 0.67 mL — an underdose that would provide insufficient analgesia. Another error involves confusing the total vial volume (2 mL) for the dose volume; the vial size is irrelevant to the calculation unless it is used to confirm the dose does not exceed the vial contents. Since 1.5 mL is less than the 2 mL vial capacity, the dose is feasible. Ketorolac is an NSAID given intramuscularly for short-term postoperative pain; accurate dosing is important to achieve adequate pain relief while minimizing renal and GI side effects associated with higher doses.