diuretics.pdf

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CHAPTER

2012 The McGraw-Hill Companies, Inc. All rights reserved.

25Diuretics


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Learning Outcomes

25.1 Explain the role of the kidneys in waterexcretion.

25.2 Describe the difference between renal

filtration and renal reabsorption.25.3 Identify two areas of the renal tubules

where sodium and water transport are

connected.25.4 Explain the function of the kidney in

maintaining acid balance.

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Learning Outcomes

25.5 Explain how the action of each diureticdiffers from that of thiazide diuretics.

25.6 Explain what happens when a diuretic

becomes refractory.25.7 Explain how diuretics affect organs like

the eye and liver.

25.8 Describe three major side effects ofeach diuretic.

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Learning Outcomes

25.9 Explain the clinical use and clinically

significant terms associated with

diuresis and diuretics.

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Clinical Indication

Diuretics are used to treat anuria,hypertension, and edema.

There are six classes of diuretics: Osmotic agents

Carbonic anhydrase inhibitors

Thiazide and thiazide-like compounds

Organic acids

Potassium-sparing diuretics

ADH antagonists

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Renal Function

The kidneys are responsible for urineproduction.

The working units of the kidney are

known as nephrons.

The nephron is composed of several

segments. Urine is produced through filtration,

reabsorption, and secretion.

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Renal Function

The renal mechanism for waterconservation is dependent upon

tubular reabsorption of sodium ions.

The nephrons secrete hydrogen ions,

potassium ions, and weak acids andbases to regulate acid-base balance

of the body.

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8/42 2012 The McGraw-Hill Companies, Inc. All rights reserved.

Renal Function Along thenephron,

sodium ions

are

reabsorbed by

twomechanisms:

Cation

exchangeChloride ion

transport

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Renal Function

Glomerulus: In thekidney, a tiny ball-

shaped structure

composed ofcapillary blood

vessels actively

involved in the

filtration of the

blood to form urine.

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Renal Function

Proximal Convoluted

Tubules: (PCT)

Cation exchange:

sodium (Na+) for

hydrogen (H+) viacarbonic anhydrase

(CAH)

Secretion of weak

acids and bases into

urine (effects other

meds, eg. Aspirin,

and waste)

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Renal Function

Loop of Henle

Sodium ions

reabsorbed via

chloride ions are

actively reabsorbedand sodium ions

follow

Osmotic gradient isestablished and waterfollows.

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Renal Function

Distal ConvolutedTubules (DCT)

Hydrogen ion

exchange via CAH

Secretion of

potassium ions (K+)

via aldosterone,

sodium (Na+)reabsorbed

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Renal Dysfunction

Renal disease and cardiovasculardysfunction alter the functioning of the

kidney, leading to: Decreased urine flow

Decreased urine volume (oliguria)

No urine production (anuria)

Uremia Edema

Hypotension

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Metabolic Acidosis

Metabolic acidosis itself usually causesrapid breathing. Confusion or lethargy may

also occur. Severe metabolic acidosis can

lead to shock or death. In some situations,metabolic acidosis can be a mild, chronic

(ongoing) condition.

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Alkalosis

Metabolic alkalosis is caused by too muchbicarbonate in the blood.

Hypokalemic alkalosis is caused by the

kidneys' response to an extreme lack orloss of potassium, which can occur when

people take certain diuretic medications.

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Symptoms and complications

Confusion (can progress to stupor or coma) Hand tremor

Lightheadedness

Muscle twitching Nausea, vomiting

Numbness or tingling in the face or

extremities Prolonged muscle spasms (tetany)

Arrhythmia

Seizures

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Osmotic Diuretics

Filtered by glomerulus but not reabsorbedby renal tubules, creating osmotic gradient.

Stimulate urine flow, producing mild

diuresis with no electrolyte imbalance.

Treatment for anuria and oligouria

Adverse effects include nausea, dizziness,

headache, and chills. Mannitol is contraindicated

in patients with edema from cardiovascular

insufficiency, pulmonary edema, or intracranial

bleeding.

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Osmotic Diuretics

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Osmotic Diuretics

Common Drugs: Glycerin (oral)

Isosorbide (oral)

Mannitol (Osmitrol) IVAcute renal failure or cardiovascular

surgeries

Cerebral edema and glaucoma

Increase flow to help excrete toxic

substance

Urea IV

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Carbonic Anhydrase Inhibitors

Increase sodium and water excretionby inhibiting carbonic anhydrase: No hydrogen ions to exchange for sodium

ions Decreased sodium reabsorption

Sodium ions and increased water excreted in

urine

Increased loss of potassium in urine

Decreased bicarbonate in blood (acidosis)

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Used in the treatment of CHF or drug-induced edema

Reduce pressure with glaucoma (stop

production of aqueous humor) Useful in the treatment of epilepsy (acidosis)

Adverse effects:

Drowsiness Headache

GI distress

Acidosis

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Common

Drugs:

Acetazolamide

(Diamox)

Methazolamide

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Osmotics/Carbonic Anhydrase Inhibitors

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Thiazide and Thiazide-like Diuretics

Inhibit sodium transport in the distal

portion of the nephron, causing substantial

loss of sodium and water

Produce intense diuresis

Can eliminate edema of any cause

Useful in treatment of mild to moderate

hypotension

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Mobilization of sodium causes potassiumexcretion as well (hypokalemia).

Side effects include:

Hyponatremia

Orthostatic hypotension

Hyperglycemia

Muscle spasms or cramps

GI distress

Headache

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Thiazide: Chlorothiazide (Diuril)

Hydrochlorothiazide (Ezide, HydroDIURIL,

Hydro-par) Methyclothiazide (Enduron, Aquatensen)

Thiazide-like Diuretics:

Chlorthalidone (Hygroton, Thalitone) Indapamide (Lozol)

Metolazone (Zaroxolyn)

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Organic Acid Diuretics

Inhibit sodium and chloride ion transport inthe loop of Henle

Tremendous loss of sodium, chloride, and

water (greater action than thiazides) Highly bound to plasma proteins

Used for treatment of edema in patients

who have become thiazide resistant Useful in severe peripheral and pulmonary

edema assoc. CHF, liver dz, & renal dz.

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Organic Acid Diuretics

Side effects are similar to thiazidediuretics:

Nausea

Hypotension Hypokalemia

Hyperuricemia

Hyperglycemia Additional side effects include:

Ototoxicity (when combined withaminoglycoside antibiotics)

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Organic Acid Diuretics (loop)

Bumatanide (Bumex)

Ethacrynic acid (Edcrin)

Furosemide (Lasix)

Torsemide (Demadex)

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Potassium-Sparing Diuretics

Inhibit potassium secretion in DCT

Produce mild diuresis without electrolyte

or acid-base disturbances

Side effects:

Nausea

Diarrhea Hyperkalemia

Gynecomastia

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Potassium-Sparing Diuretics

Amiloride (Midamor) Caution with hyperkalemia

Spironolactone (Aldactone)

Adjunct therapy for hypertension Potential issue with tumor development over

long term use

Triamterene (Dyrenium)Adjunct therapy for hypertension

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Organic Acid/Potassium-Sparing Diuretics

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ADH Antagonists

ADH regulates water balance in thebody. (monitored in the hypothalamus Na+,excreted by the posterior pituitary, controls

aquaporins) ADH antagonists block the ADH

receptors in the kidneys.

Inhibition of ADH receptors causesexcretion of free water without

electrolyte loss. (aquaresis)

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ADH Antagonists

Conivaptan

Lixivaptan

Tolvaptan

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Miscellaneous Diuretics

Xanthine derivatives are naturallyoccurring drugs that produce mild

diuretic responses. (caffeine, pamabrom,

theobromine, theophylline)

They stimulate urine flow by

increasing blood flow to kidneys.

Side effects include CNS stimulation,

hypotension, and headache.

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Special Considerations

Most diuretics cause electrolyte andacid-base imbalance: Potassium loss is most common.

Patients should supplement potassium.

Blood pressure may be altered.

Blood glucose levels may be altered.

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Drug Interactions and Incompatibilities

Diuretics are involved in a number ofdrug interactions due to their MOA: Bind to plasma proteins

Alter acid-base balance Stimulate renal excretion

Diuretics when mixed in IVs withother solutions can cause precipitate

formation.

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Preferred Treatment

ADH Antagonists

Euvolemic andhypervolemichyponatremia

CarbonicAnhydraseInhibitors

Glaucoma, edemawith alkalosis and

mountainsickness

Loop Diuretics

Pulmonary andperipheral edema,hypertension and

acute renal failure

Thiazides

Hypertension,mild heart failure,

andnephrolithiasis

Osmotic Diuretics

Improve renalfailure, reduceintracranialpressure,glaucoma

Potassium-

sparing DiureticsHypokalemia dueto other diuretics

and post MI

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