A 55-year-old male with bipolar I disorder has been maintained on lithium 900 mg daily with stable levels of 0.8 mEq/L for three years. He presents to the clinic reporting a two-week history of taking ibuprofen 600 mg three times daily for knee osteoarthritis pain prescribed by his primary care provider. He reports new-onset fine tremor, increased thirst, nausea, and intermittent loose stools. A stat lithium level returns at 1.6 mEq/L. Which of the following best explains the mechanism by which ibuprofen elevated this patient's lithium level?