Final answer:
A patient with a potassium level of 2.1 on Lasix would likely be switched to spironolactone (Aldactone), a potassium-sparing diuretic, to correct hypokalemia.
Step-by-step explanation:
A patient with a potassium level of 2.1 has been taking Lasix (furosemide), which is a potent diuretic often prescribed for managing fluid retention and hypertension. Lasix works mainly on the loop of Henle in the kidneys, inhibiting the reabsorption of sodium (Na+) and chloride (Cl-), which in turn leads to increased urine production. However, excessive use of Lasix can lead to the depletion of important electrolytes, including potassium, resulting in a condition known as hypokalemia.
Given the patient's low potassium levels, a physician may consider switching from Lasix to a potassium-sparing diuretic to avoid further potassium loss. The likely substitute would be spironolactone (Aldactone), which helps the body to retain potassium. Spironolactone works by antagonizing the hormone aldosterone, leading to reduced excretion of potassium, and is commonly prescribed when there is a need to correct hypokalemia. The other options listed, such as hydrochlorothiazide and Demadex, also promote the excretion of potassium and would not be suitable choices for a patient with already low potassium levels.