Bone Loss Prevention With Zoledronic Acid or Denosumab in Critically Ill Adults

Inclusion Criteria: * Female age ≥ 50 years or male age ≥ 70 years * Has been in the Intensive Care Unit for 2 or more calendar days and is not expected to be discharged from the Intensive Care Unit on the second day * Has required Intensive Care Unit level support (i.e. intravenous vasoactive drugs, or invasive mechanical ventilation, or non-invasive ventilation or high flow nasal oxygen at Fraction inspired Oxygen ≥0.4 and/or gas flows ≥40L/m) for a minimum cumulative duration of 6 hours * Expected to survive the current hospital admission Exclusion Criteria: * Cancer related metastatic bone disease or multiple myeloma * Paget's disease * Pregnancy * Current estimated Glomerular Filtration Rate \<30ml/min or receiving renal replacement therapy * Known contraindication to denosumab or zoledronic acid * Obvious holes in teeth or broken teeth or dental or gum infection * Known untreated hypoparathyroidism * Current treatment with anti-fracture agent (bisphosphonate, strontium or teriparatide within previous 2 years, or menopausal hormone therapy or romosozumab within previous 12-months or denosumab within previous 6 months) * Current fragility fracture of hip, spine, femur or forearm * Exceeds weight limit for BMD scan at site or unable to undertake Bone Mineral Density for any reason * International Normalised Ratio \> 3.0 or Platelet count \< 30 10\^9/L