Transcript Pharmacology and the Nursing Process, 4th ed

CHAPTER 26
Diuretic Drugs
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Diuretic Drugs
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
Drugs that accelerate the rate of urine
formation
Results in the removal of sodium and water
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Sodium

In the nephron, where sodium goes, water
follows
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
20% to 25% of all sodium is reabsorbed
into the bloodstream in the ascending loop of
Henle
 5% to 10% is reabsorbed in the distal convoluted
tubules
 3% is reabsorbed in collecting ducts
If water is not absorbed, it is excreted as urine
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Types of Diuretic Drugs
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Carbonic anhydrase inhibitors
Loop diuretics
Osmotic diuretics
Potassium-sparing diuretics
Thiazide and thiazide-like diuretics
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Carbonic Anhydrase Inhibitors
(CAIs)
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
acetazolamide (Diamox)
methazolamide (Neptazane)
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Carbonic Anhydrase Inhibitors:
Mechanism of Action
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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
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Carbonic Anhydrase Inhibitors:
Mechanism of Action (cont’d)
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Inhibition of carbonic anhydrase reduces H+
ion concentration in renal tubules
As a result, there is increased excretion of
bicarbonate, sodium, water, and potassium
Resorption of water is decreased, and urine
volume is increased
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Carbonic Anhydrase Inhibitors:
Indications
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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:
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
Edema
Epilepsy
High-altitude sickness
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Carbonic Anhydrase Inhibitors:
Indications (cont’d)
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Acetazolamide 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
to 4 days
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Carbonic Anhydrase Inhibitors:
Adverse Effects
Metabolic acidosis
 Anorexia
 Hematuria
 Photosensitivity
 Melena

Hypokalemia
 Drowsiness
 Paresthesias
 Urticaria

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Loop Diuretics
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bumetanide (Bumex)
furosemide (Lasix)
torsemide (Demedex)
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Loop Diuretics:
Mechanism of Action
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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
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Loop Diuretics: Drug Effects
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Potent diuresis and subsequent loss of fluid
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Decreased fluid volume causes a reduction
in:
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BP
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Pulmonary vascular resistance
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Systemic vascular resistance
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Central venous pressure
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Left ventricular end-diastolic pressure
Potassium and sodium depletion
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Loop Diuretics:
Indications
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Edema associated with HF or hepatic
or renal disease
To control hypertension
To increase renal excretion of calcium in
patients with hypercalcemia
In cases of HF resulting from diastolic
dysfunction
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Loop Diuretics: Adverse Effects
Body System
CNS
Adverse Effects
Dizziness, headache,
tinnitus, blurred vision
GI
Nausea, vomiting,
diarrhea
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Loop Diuretics:
Adverse Effects (cont’d)
Body System
Hematologic
Adverse Effects
Agranulocytosis,
neutropenia,
thrombocytopenia
Metabolic
Hypokalemia,
hyperglycemia,
hyperuricemia
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Osmotic Diuretics

mannitol (Osmitrol)
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Osmotic Diuretics:
Mechanism of Action
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Work mostly in the proximal tubule
Nonabsorbable, producing an osmotic effect
Pull water into the renal tubules from the
surrounding tissues
Inhibit tubular resorption of water and solutes,
thus producing rapid diuresis
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Osmotic Diuretics:
Drug Effects
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Increases glomerular filtration rate and renal
plasma flow—helps to prevent kidney
damage during acute renal failure
Reduces excessive intraocular pressure
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Osmotic Diuretics:
Indications
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Treatment of patients in the early, oliguric
phase of ARF
To promote excretion of toxic substances
To reduce intracranial pressure
Treatment of cerebral edema
NOT indicated for peripheral edema
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Osmotic Diuretics:
Adverse Effects
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Convulsions
Thrombophlebitis
Pulmonary congestion
Also headaches, chest pains, tachycardia,
blurred vision, chills, and fever
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Osmotic Diuretics:
Mannitol
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Intravenous infusion only
May crystallize when exposed to low
temperatures—use of a filter is required
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Potassium-Sparing Diuretics
amiloride (Midamor)
 spironolactone (Aldactone)
 triamterene (Dyrenium)
Also known as aldosterone-inhibiting diuretics
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Potassium-Sparing Diuretics:
Mechanism of Action
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Work in collecting ducts and distal convoluted
tubules
Interfere with sodium-potassium exchange
Competitively bind to aldosterone receptors
Block resorption of sodium and water usually
induced by aldosterone
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Potassium-Sparing Diuretics:
Drug Effects
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Prevent potassium from being pumped into
the tubule, thus preventing its secretion
Competitively block aldosterone receptors
and inhibit their action
Promote the excretion of sodium and water
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Potassium-Sparing Diuretics:
Indications
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spironolactone and triamterene
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Hyperaldosteronism
Hypertension
Reversing potassium loss caused by
potassium-losing drugs
Certain cases of HF
amiloride
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Treatment of HF
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Potassium-Sparing Diuretics:
Adverse Effects
Body System
Adverse Effects
CNS
Dizziness, headache
GI
Cramps, nausea,
vomiting, diarrhea
Other
Urinary frequency,
weakness, hyperkalemia
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Potassium-Sparing Diuretics:
Adverse Effects (cont’d)
spironolactone
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Gynecomastia
Amenorrhea
Irregular menses
Postmenopausal bleeding
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Thiazide and Thiazide-like
Diuretics
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Thiazide diuretics
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hydrochlorothiazide (Esidrix, HydroDIURIL)
chlorothiazide (Diuril)
trichlormethiazide (Metahydrin)
Thiazide-like diuretics

metolazone (Mykrox, Zaroxolyn)
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Thiazide and Thiazide-like
Diuretics: Mechanism of Action
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Inhibit tubular resorption of sodium, chloride,
and potassium ions
Action primarily in the distal convoluted tubule
Result: water, sodium, and chloride are
excreted
Potassium is also excreted to a lesser extent
Dilate the arterioles by direct relaxation
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Thiazide and Thiazide-like
Diuretics: Drug Effects
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Lowered peripheral vascular resistance
Depletion of sodium and water (and
potassium)
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Thiazide and Thiazide-like
Diuretics (cont’d)
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Thiazides should not be used if creatinine
clearance is less than 30 to 50 mL/min
(normal is 125 mL/min)
Metolazone remains effective to a creatinine
clearance of 10 mL/min
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Thiazide and Thiazide-like
Diuretics: Indications
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Hypertension (one of the most prescribed
group of drugs for this)
Edematous states
Idiopathic hypercalciuria
Diabetes insipidus
Heart failure due to diastolic dysfunction
Adjunct drugs in treatment of edema related
to HF, hepatic cirrhosis, or corticosteroid or
estrogen therapy
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Thiazide and Thiazide-like
Diuretics: Adverse Effects
Body System
CNS
Adverse Effects
Dizziness, headache,
blurred vision,
paresthesias,
decreased libido
GI
Anorexia, nausea,
vomiting, diarrhea
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Thiazide and Thiazide-like
Diuretics: Adverse Effects
(cont’d)
Body System
GU
Integumentary
Metabolic
Adverse Effects
Impotence
Urticaria,
photosensitivity
Hypokalemia,
glycosuria,
hyperglycemia
hyperuricemia
Others
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Nursing Implications
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Perform a thorough patient history and
physical examination
Assess baseline fluid volume status, intake
and output, serum electrolyte values, weight,
and vital signs—especially postural BPs
Assess for disorders that may contraindicate
or necessitate cautious use of these drugs
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Nursing Implications (cont’d)
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Instruct patients to take the medication in the
morning if possible to avoid interference with
sleep patterns
Monitor serum potassium levels during
therapy
Potassium supplements are usually not
recommended when potassium levels exceed
3 mEq/L
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Nursing Implications (cont’d)
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Teach patients to maintain proper nutritional
and fluid volume status
Teach patients to eat more potassium-rich
foods when taking any but the potassiumsparing drugs
Foods high in potassium include bananas,
oranges, dates, apricots, raisins, broccoli,
green beans, potatoes, meats, fish, and
legumes
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Nursing Implications (cont’d)
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Patients taking diuretics along with a digitalis
preparation 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
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Nursing Implications (cont’d)
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Teach patients to change positions slowly
and to rise slowly after sitting or lying to
prevent dizziness and fainting related to
orthostatic hypotension
Encourage patients to keep a log of their
daily weight
Remind patients to return for follow-up visits
and labwork
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Nursing Implications (cont’d)
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Patients who have been ill with nausea,
vomiting, and/or diarrhea should notify their
physician because fluid loss may be
dangerous
Signs and symptoms of hypokalemia include
muscle weakness, constipation, irregular
pulse rate, and overall feeling of lethargy
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Nursing Implications (cont’d)
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Instruct patients to notify their physician
immediately if they experience rapid heart
rates or syncope (reflects hypotension or fluid
loss)
A weight gain of 2 or more pounds a day
or 5 or more pounds a week should be
reported immediately
Excessive consumption of licorice can lead to
additive hypokalemia in patients taking
thiazides
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Nursing Implications (cont’d)
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Monitor for adverse effects:
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Metabolic alkalosis, drowsiness, lethargy,
hypokalemia, tachycardia, hypotension, leg
cramps, restlessness, decreased mental alertness
Monitor for hyperkalemia with potassiumsparing diuretics
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Nursing Implications (cont’d)
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Monitor for therapeutic effects
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Reduction of edema, fluid volume overload, HF
Reduction of hypertension
Return to normal intraocular pressures
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