DiureticsLilley Reading & Workbook, Chap 25

Drugs that accelerate the rate of urine formation

In the nephron, where sodium goes, water follows◦ 20% to 25% of all sodium is reabsorbed into the

bloodstream in the ascending loop of Henle◦ 5% to 10% in the distal convoluted tubules◦ 3% in collecting ducts

If water is not absorbed, it is excreted as urine Result: removal of sodium and water

Carbonic anhydrase inhibitors Loop diuretics Osmotic diuretics Potassium-sparing diuretics Thiazide and thiazide-like diuretics

The enzyme carbonic anhydrase helps to make H+ ions available for exchange with sodium and water in the proximal tubules

CAIs ◦ block the action of carbonic anhydrase, ◦ thus preventing the exchange of H+ ions with sodium and water◦ reduces H+ ion concentration in renal tubules

Result: ◦ increased excretion of bicarbonate, sodium, water, & K+ ◦ Resorption of water is decreased and urine volume is increased

acetazolamide (Diamox) methazolamide dichlorphenamide

Adjunct drugs in the long-term management of open-angle glaucoma*

Used with miotics to lower intraocular pressure before ocular surgery in certain cases

Also useful in the treatment of:◦ Edema* ◦ Epilepsy◦ High-altitude sickness

Acetazolamide (Diamox) is used in the management of edema secondary to HF when other diuretics are not effective*

CAIs are less potent diuretics than loop diuretics or thiazides—the metabolic acidosis they induce reduces their diuretic effect in 2-4 days

Metabolic acidosis Anorexia Hematuria Photosensitivity Melena

HypokalemiaHypokalemia DrowsinessDrowsiness ParesthesiasParesthesias UrticariaUrticaria

Act directly on the ascending limb of the loop of Henle to inhibit chloride and sodium resorption

Increase renal prostaglandins, resulting in the dilation of blood vessels and reduced peripheral vascular resistance

bumetanide (Bumex) ethacrynic acid (Edecrin) furosemide (Lasix)

Potent diuresis and subsequent loss of fluid Decreased fluid volume causes:

◦ Reduced BP

◦ Reduced pulmonary vascular resistance

◦ Reduced systemic vascular resistance

◦ Reduced central venous pressure

◦ Reduced left ventricular end-diastolic pressure

Potassium and sodium depletion

Edema associated with HF or hepatic or renal disease

Control of hypertension

Increase renal excretion of calcium in patients with hypercalcemia

Certain cases of HF resulting from diastolic dysfunction

Body System Adverse EffectsCNS Dizziness, headache,

tinnitus, blurred vision

GI Nausea, vomiting, diarrheaHematologic Agranulocytosis, neutropenia, thrombocytopenia

Metabolic Hypokalemia, hyperglycemia,hyperuric

Work mostly in the proximal tubule

Nonabsorbable, producing an osmotic effect

Pull water into renal tubules from the surrounding tissues

Inhibits tubular resorption of water and solutes

Increases glomerular filtration and renal plasma

Reduces excessive intraocular pressure

Used in the treatment of patients in the early, oliguric phase of ARF

To promote the excretion of toxic substances

Reduction of intracranial pressure

Treatment of cerebral edema

NOT indicated for peripheral edema

Convulsions

Thrombophlebitis

Pulmonary congestion

Also headaches, chest pains, tachycardia, blurred vision, chills, and fever

mannitol (Osmitrol)

Intravenous infusion only

May crystallize when exposed to low temperatures—use of a filter is required

Interfere with sodium-potassium exchange in collecting ducts and convoluted tubules

Competitively bind to aldosterone receptors◦ Block the resorption of sodium and water

Prevent potassium from being pumped into the tubule, thus preventing its secretion

Competitively block the aldosterone receptors and inhibit its action

Sodium and water are excreted

amiloride (Midamor) spironolactone (Aldactone) triamterene (Dyrenium)

Also known as aldosterone-inhibiting diuretics

spironolactone and triamterene

◦ Hyperaldosteronism◦ Hypertension◦ Reversing the potassium loss caused by potassium-losing

drugs◦ Certain cases of heart failure◦ Liver failure

Amiloride

◦ Treatment of HF

Body System Adverse Effects

CNS Dizziness, headache

GI Cramps, nausea, vomiting, diarrhea

Other Urinary frequency,weakness

**hyperkalemia**

Spironolactone

Gynecomastia Amenorrhea Irregular menses Postmenopausal bleeding

Actions: Acts in the distal convoluted tubule

◦ Inhibit tubular resorption of sodium, chloride, and potassium ions

◦ Result: water, sodium, and chloride are excreted Potassium is also excreted to a lesser extent Dilate the arterioles by direct relaxation

Results:◦ Lowered peripheral vascular resistance◦ Sodium, water, chloride and potassium are excreted

Thiazide diuretics◦ hydrochlorothiazide (Esidrix, HydroDIURIL)◦ chlorothiazide (Diuril)◦ trichlormethiazide (Metahydrin)

Thiazide-like diuretics◦ chlorthalidone (Hygroton)◦ metolazone (Mykrox, Zaroxolyn)

Thiazides should not be used if creatinine clearance is less than 30 to 50 mL/min (normal is 125 mL/min)

Metolazone (Zaroloxyn) remains effective to a creatinine clearance of 10 mL/min

Hypertension – first line drug for HTN

Edematous states

Idiopathic hypercalciuria

Diabetes insipidus

Heart failure due to diastolic dysfunction

Adjunct drugs in treatment of edema related to HF, hepatic cirrhosis, corticosteroid therapy

Body System Adverse Effects

CNS Dizziness, headache, blurred vision, paresthesias, decreased libido

GI Anorexia, nausea, vomiting, diarrhea

GU Impotence

Integumentary Urticaria, photosensitivity

Metabolic Hypokalemia, glycosuria, hyperglycemia, hyperuricemia

OTHER EFFECTS ALSO

Thorough patient history and physical examination

Assess baseline fluid volume status, intake and output, serum electrolyte values, weight, and vital signs—especially postural BPs/orthostatic BPs

Assess for disorders that may contraindicate or necessitate cautious use of these drugs

Monitor serum K+ levels during therapy◦ K+ supplements are usually recommended to maintain

K+ levels at approximately 4 mEq/L

Instruct patients to take in the morning as much as possible to avoid interference with sleep patterns

Teach patients to maintain proper nutritional and fluid volume status

Teach patients to eat more potassium-rich foods when taking any but the potassium-sparing drugs

Foods high in potassium include bananas, oranges, dates, raisins, plums, fresh vegetables, potatoes, meat, and fish, apricots, whole grain cereals, legumes

Patients taking diuretics along with a digitalis preparation digoxin (Lanoxin) should be taught to monitor for digitalis toxicity

Diabetic patients who are taking thiazide and/or loop diuretics should be told to monitor blood glucose and watch for elevated levels

Change positions slowly, and to rise slowly after sitting or lying to prevent dizziness and possible fainting related to orthostatic hypotension

Encourage patients to keep a log of their daily weight

A weight gain of 2 or more pounds a day or 5 or more pounds a week should be reported immediately

Encourage patients to return for follow-up visits and labwork

Notify physician if you are ill with nausea, vomiting, and/or diarrhea because fluid loss may be dangerous

Excessive consumption of licorice can lead to an additive hypokalemia in patients taking thiazides

Signs and symptoms of hypokalemia include muscle weakness, constipation, irregular pulse rate, and overall feeling of lethargy

Notify the physician immediately if rapid heart rate or syncope occurs (reflects hypotension or fluid loss)

Diuretics are used for which of the followingreasons? (Select all that apply.)

1. treat hypertension2. treat edema with heart failure3. increase urine fl ow4. treat hyperuricemia (increased uricacid level)

Potassium-sparing diuretics are administeredin combination with other typesof diuretics to do which of the following?

(Select all that apply.)1. treat hypertension2. treat heart failure3. prevent hypokalemia4. prevent hyperkalemia

The most potent class of diuretics currentlyavailable is:

1. thiazide-type.2. potassium-sparing type.3. loop-type.4. carbonic anhydrase inhibitor.

Patients with diabetes mellitus receiving adiuretic should be observed for:

1. hypoglycemia.2. hyperglycemia.3. hyperkalemia.4. normonatremia.