diuretics lilley reading & workbook, chap 25. drugs that accelerate the rate of urine formation...
TRANSCRIPT
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.