All concepts, explanations, trials, and studies have been re-written in plain English and may contain errors. I am not a doctor ----------------------------------------------------------- NOTE: You can make the print bigger with the font button on your browser! (It's usually a big "A") ----------------------------------------------------------- DIURETICS Dr. Christian Mende is board certified in internal medicine, nephrology and geriatrics. He discussed techniques to improve diuretic use at the Second Annual U.S. Geriatric and Long-Term Care Congress in Las Vegas. "Diuretics are compounds that increase urinary salt elimination, and water just happens to come along," he said. Each class of diuretics has a distinct site of action in the kidney : 1) acetazolamide (Diamox) works in the proximal tubule. 2) furosemide (Lasix), Bumex, Edecrine, and torsemide (Demadex) work in the loop of Henle. 3) thiazide diuretics like Zaroxolyn and hydrochlorothiazide block reabsorption of sodium in the early distal tubule. 4) Potassium-sparing diuretics such as amiloride (Midamor), triamterene (Dyrenium), and spironolactone (Aldactone) act in the collecting duct, preventing some exchange of sodium for potassium that happens there. As soon as diuretics start working, your body begins to counteract the process. "Your body very quickly - by the second and third doses - has less of a response to the diuretic," Mende explained. Your body tries to maintain the current amount of fluid in your body by producing more renin ; by reducing kidney blood flow ; by activating the sodium/potassium pump ; and by producing more aldosterone. To help reduce the body's defenses against a diuretic, 2 or 3 different types of diuretics may be used at the same time. "You use a loop diuretic plus a thiazide together, and you could add triamterene or Aldactone to that. Then you have 3 different diuretics blocking. We call this sequential nephron blocking," said Mende. Patients may lose a lot of potassium this way, so electrolytes need to be carefully monitored. SPECIFIC DIURETICS MANNITOL AND ACETAZOLAMIDE Mannitol is for IV use only. It is used mainly in trauma when patients have low blood pressure and inability to pee ; during aneurysm repair ; to reduce brain swelling ; as an antidote for some food poisoning (mainly from fish), etc. Mannitol is not used for chronic edema because it doesn't cause a lot of sodium elimination. Acetazolamide inhibits hydrogen ions and lowers blood levels of bicarbonate. The diuretic action of this drug stops when bicarbonate blood levels drop below 22 mEq/L. Uses include uric acid kidney disease, and aspirin or barbiturate overdose. It can be used to correct high bicarbonate levels in hospitalized heart failure patients. THIAZIDES "If you use hydrochlorothiazide for high blood pressure and edema in a patient with creatinine levels above 2 mg/dL, little happens. It just doesn't work if kidney function is less than 30%," Mende said. "Metolazone works all the way down to 10% of kidney function. If creatinine is 2 mg/dL or higher, you have 2 choices : metolazone or a loop diuretic." If thiazides are used for high blood pressure and to reduce urinary calcium loss in kidney stone formers, doses of 12.5mg to 25mg are enough. The number one side effect of thiazides is too-high calcium levels. "If someone has high calcium, look at their drugs and they are usually on a thiazide. Stop the thiazide and give them Lasix or Bumex, which reduce calcium. If the calcium comes back to normal, it was the thiazide. If the calcium does not come back to normal within a week, that person needs a thyroid test." Other side effects of thiazides include sensitivity to light, and pancreas and white blood cell problems. LOOP DIURETICS Although different loop diuretics work at different sites in the kidney, Mende said, "If you give someone 40mg per day Lasix and at the same time 2mg per day Bumex, you are wasting one - please decide which one you want to use." Loop diuretics "are very potent even in people with terrible kidney function," Mende said. The higher the creatinine level, the higher the dose of loop diuretics needed. For patients with acute pulmonary edema, Mende said he uses IV Bumex, which works within 5 minutes. It relaxes blood vessels and lowers pressures. For heart failure patients, Mende said he uses a loop diuretic instead of a thiazide because, "you need a powerful diuretic to deal with the edema, low cardiac output and reduced kidney function." Mende uses a twice-a-day dose of loop diuretics in CHFers. "You are better off to dose twice a day because the drug only works for 8 hours and the other 16 hours, the kidneys hold onto salt and water," he said. Often, Mende will combine types of diuretics. Mende warned that if a patient's blood sodium level falls below 120 mEq/L, don't try to correct the levels in one day. If you do it faster than 12 mEq/L per 24 hours, the patient may suffer irreversible damage to nerve fibers. POTASSIUM SPARING DIURETICS Potassium-sparing diuretics are weak diuretics because they work in the kidney's collecting ducts where only 3% of the load is processed. They are mainly used along with thiazides and loop diuretics. Besides getting rid of fluid, spironolactone also reduces scarring and fibrosis in the heart. By reducing scarring and fibrosis, you also reduce arrhythmias seen with CHF. Amiloride can be used for low magnesium because it increases kidney reabsorption. If somebody has low magnesium and you can't give them enough magnesium orally because of laxative action, amiloride is an option. Specific side effects seen with potassium- sparing diuretics include high potassium levels, swollen and painful breasts (even in men), impotence, and irregular menstrual cycles. NOTES You can neutralize any diuretic by high sodium intake, so stay on a low-sodium diet. Drink only when you are thirsty, unless exercising. Potassium levels should be kept at 3.5 mEg/L or higher in CAD patients with a history of arrhythmias, during anesthesia, and in patients with diabetes. Magnesium levels should stay in the high normal range to reduce arrhythmias, especially in heart attack patients. Nearly all diuretics come from sulfa drugs. Sensitive patients can use ethacrynic acid if it is available. NSAIDs like aspirin, ibuprofen and Aleve reduce diuretic effectiveness by up to 30% because they hold on to salt and water and block prostaglandins. For patients with severe CHF who are taking diuretics, don't forget elevating the legs and using compression in the form of elastic bandages or stockings. Source: www.geriatrictimes.com/g010327.html From: Geriatric Times, March/April 2001 Vol. II Issue 2 Title: A Fresh Look at Diuretics (Excerpts, Edited) Author: Arline Kaplan Reference: Mende CW (1990), Current issues in diuretic therapy. Hosp Pract (Off Ed) 25(suppl 1):15-21.