Nursing Pharmacology Chapter 26:  Renal Pharmacology

Mechanisms whereby furosemide and thiazides are useful in calcium metabolism disorders management

Role of Diuretics in Calcium Metabolism

• Loop Diuretics and Calcium Metabolism

  • Furosemide (Lasix)

  • Torsemide (Demadex)

  • Bumetanide (Bumex)

• Mechanism of action

  • Inhibition of NaCl reabsorption in the thick ascending limb of the loop of Henle

    • inhibit the Na/K/2Cl transport system in the luminal membrane

      1. reduction in sodium chloride reabsorption

      2. decreases normal lumen-positive potential (secondary to potassium recycling)

      3.  Positive lumen potential: drives divalent cationic reabsorption (calcium magnesium)

      4.  Therefore, loop diuretics increase magnesium and calcium excretion.

         • Hypomagnesemia may occur in some patients.

         • Hypocalcemia does not usually develop because calcium is reabsorbed in the distal convoluted tubule.

           •   In circumstances that result in hypercalcemia, calcium excretion can be enhanced by administration of loop diuretics with saline infusion

    • Clinical Uses:

      •  Major uses:

        •  Acute pulmonary edema

        •  Acute hypercalcemia

        •  Management of edema

Thiazides and Calcium Metabolism

• Mechanism of action

  • Diuretic action:  Inhibition of NaCl reabsorption from the distal convoluted tubule (luminal side)

  • Enhanced calcium reabsorption in the distal convoluted tubule.

    • Thiazides infrequently cause hypercalcemia but can unmask hypercalcemia due to other causes such as carcinoma, sarcoidosis, or hyperparathyroidism.

Jackson, E.K. Diuretics In, Goodman and Gillman's The Pharmacological Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) The McGraw-Hill Companies, Inc.,1996, pp. 685- 713

Jackson, E.K. Vasopressin and Other Agents Affecting the Renal Conservation of Water In, Goodman and Gillman's The Pharmacological Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) The McGraw-Hill Companies, Inc.,1996, pp.715-732