A. Oxytocin causes water intoxication: This synthetic peptide hormone is structurally homologous to arginine vasopressin and possesses intrinsic antidiuretic properties. High-dose infusions stimulate renal V2 receptors, increasing free water reabsorption and causing dilutional hyponatremia. Monitoring fluid balance is essential to prevent pulmonary or cerebral edema. B. Oxytocin causes excessive thirst: Polydipsia is not a recognized pharmacological side effect of this uterotonic medication. Thirst is typically a physiological response to hyperosmolarity or dehydration, which is the opposite of the water retention caused by oxytocin. The clinical priority is identifying fluid overload. C. Oxytocin is toxic to the kidneys: This medication does not cause direct nephrotoxicity or structural injury to the renal tubules or glomeruli. Its effects on the kidney are functional and reversible upon discontinuation of the drug. It does not lead to acute kidney injury. D. Oxytocin has a diuretic effect: This choice incorrectly describes the renal action of the drug. Oxytocin causes water retention rather than increased urinary excretion. It acts as an antidiuretic, necessitating vigilant assessment of intake and output to identify a positive fluid balance.