LN is 84 YOM who is in hospital for a back surgery.

LN is 84 YOM who is in hospital for a back surgery. His height is 5 feet and 4 inches, weight 85 kg and NKDA.

His past medical history includes hypertension, diabetes mellitus, major depression, hypothyroidism and chronic back pain. Post-op day 1, LN’s medication includes Dexamethasone 8mg iv q6h with taper dosing, Ondansetron 4 mg iv q6h prn for N/V, Levothyroxine 0.075 mg po daily, Lisinopril 10 mg po daily, Citalopram 20 mg po daily, Docusate sodium / Senna 1 tab po twice a day, Bisacodyl 10 mg suppository daily prn for constipation, Famotidine 20 mg iv q12hr, Metoclopramide 10mg iv q6h, Metformin 500 mg po bid, D51/2NS with 20K at 125 mls/hour and Hydromorphone PCA at 0.2mg/hour of basal rate, demand dose 0.1 mg. lock-out every 6min, one hour limit 2.2 mg/hour. Pertinent morning labs includes serum creatinine 1.4 mg/dl, Mg 1.5 mg/dl, K 5.0 mmol/L, Na 135 mmol/L.

Which of the following medication/s should LN be on to prevent the most common side effect of hydromorphone?