Potassium sparing diuretics Nursing Implications and Drug Study

POTASSIUM SPARING DIURETICS

GENERAL DESCRIPTION

Potassium sparing diuretics caused diuresis without loss of potassium unlike other diuretics. They are less potent diuretic agents therefore potassium sparing diuretics may combine with other diuretics to prevent the loss of potassium and further increase in diuretic effects.

EXAMPLE:

Potassium sparing diuretics are divided into two types according to their chemical structure and mechanism of action, as below

1) Competitive antagonists and structurally related to aldosterone: Spironolactone, Eplerenone

2. Na⁺/K⁺ exchange antagonists that do not compete with aldosterone: Amiloride, Triamterene.

SPIRONOLACTONE

GENERIC NAME: Spironolactone

BRAND NAME: Aldactone

GENERAL DESCRIPTION

Spironolactone is a synthetic steroid that act as a competitive antagonist to aldosterone. It is also called potassium sparing diuretics because it prevents the loss of potassium from the body. Prolong use of spironolactone can cause in heart failure and its use is limited when there is hyperaldosteronism whether primary or secondary. Spironolactone is marketed as combination tablets with loop or thiazide diuretics as a means of avoiding hypokalemia.

MECHANISM OF ACTION

Spironolactone indirectly inhibit the Na⁺ reabsorption. The main site of action of Spironolactone is intercalated cells in cortical collecting duct. These cells have aldosterone receptors where aldosterone binds and make sodium-potassium pumps which goes to the cell membrane and reabsorb sodium and secrete potassium. But when spironolactone binds with these receptors then antagonize the aldosterone effects and thus inhibit Na⁺/ K⁺ pump. This action cause natriuresis with loss of water and prevent excretion of potassium. Only a small portion of Na⁺ is reabsorbed by this mechanism, spironolactone is not potent diuretic agents.

PHARMACOKINETICS

Spironolactone is given orally has less bioavailability, which can increase when taken with meal. Spironolactone has very slow onset of action. Spironolactone has high protein binding. It is metabolized by the liver when given orally. Spironolactone is a prodrug and its metabolites are active and longer half-life in comparison. Spironolactone is excreted by kidney.

INDICATIONS

• Excess of mineralocorticoid
• Hyperaldosteronism (Primary or secondary)
• Heart failure
• Essential hypertension
• Hypokalemia
• Edema (caused by liver or kidney disease)

CONTRAINDICATIONS

• Liver disease
• K-supplements should be discontinued
• Chronic renal insufficiency
• Agents that blunt renin-angiotensin system (beta blockers or ACE inhibitors)

SIDE EFFECTS & ADVERSE EFFECTS

• High doses of spironolactone can cause estrogenic like side effects which are
• Gynecomastia
• Breast tenderness in men
• Irregularity in menstrual cycle
• Others are
• Hyperkalemia
• Hyperchloremic metabolic acidosis
• Acute renal stone
• Kidney stone

DRUG INTERACTION

• Digoxin or sotalol when co-prescribed with Spironolactone, can cause severe hypokalemia and increase toxicity of digoxin and sotalol.
• Spironolactone can cause hyperkalemia if used with ACEI or sartans in patients with renal impairment.
• Trimethoprim may cause hyperkalemia when given with spironolactone.
• Indomethacin reduced the diuretic effect of Spironolactone.
• Food may increase the plasma level of Spironolactone but this did not alter its antihypertensive efficiency in long term.
• Dextropropxyphene can develop gynecomastia and rashes when given with Spironolactone
• Aspirin reduced the spironolactone-induced loss of sodium.

NURSING CONSIDERATIONS AND IMPLICATIONS

• Dose should be given in early timings because of increase urination.
• Obtain complete health history (Electrolyte balance & renal function)
• Obtain vital signs with the baseline values specially Blood pressure
• Find out patient’s medication history including alcohol and nicotine consumption to avoid drug interaction
• Determine possible drug allergies of patient.
• Obtain blood and urine specimen for laboratory analysis
• Observe for any change in consciousness, dizziness, fatigue, postural hypotension
• Monitor for fluid intake by measuring intake, output and daily weight.
• Monitor laboratory values specially potassium and sodium levels, BUN, Serum Uric acid.

PATIENT EDUCATION

• Reduce dietary intake of potassium or potassium supplements or ask HP
• Do not breast feed while taking the medicine.
• Explain the right use of medicine with dosage
• Report any visible s/s of proximal edema, SOB, potential sign of Heart Failure or Pulmonary edema
• Report immediate if feeling dizzy or change in consciousness
• Advise them to change position slowly to avoid postural hypotension
• Monitor BP as specified by the HP
• Mention possible side effects that can cause by the use of diuretics such as dry mouth, increase in urination.
• Ask health care professional before taking any vitamin/minerals or other supplements
• When outdoor, wear dark glasses or light color clothe because some diuretics cause photosensitivity.

AMILORIDE

GENERIC NAME: Amiloride

BRAND NAME: Midamor

GENERAL DESCRIPTION

Amiloride is a potassium sparing diuretic. Amiloride blocks the epithelial sodium channel thereby inhibits sodium reabsorption at this site and prevent loss of potassium thus called potassium sparing diuretics. Amiloride is marketed as combination tablets with loop or thiazide diuretics as a means of avoiding hypokalemia.

MECHANISM OF ACTION

Amiloride is direct inhibitors of Na⁺ influx in the late distal convoluted tubule and collecting duct in the renal nephron. It blocks the epithelial sodium channel and inhibits sodium reabsorption at this site and prevent loss of potassium which in result inhibits the exchange of sodium and potassium at the Na⁺/ K⁺ pump. Only a small portion of Na is reabsorbed by this mechanism, Amiloride is not potent diuretic agent.

PHARMACOKINETICS

Amiloride is given orally. It is metabolized in the liver but major route of elimination is renal excretion. Amiloride is longer half-life than Triamterene.  It is excreted un-metabolized in the urine and feces. Peak serum levels are seen at three hours, and the serum half-life is six hours.

INDICATIONS

• Excess of mineralocorticoid
• Hyperaldosteronism (Primary or secondary)
• Heart failure
• Essential hypertension
• Hypokalemia
• Edema (caused by liver or kidney disease)

CONTRAINDICATIONS

• K-supplements should be discontinued
• Chronic renal insufficiency
• Agents that blunt renin-angiotensin system (beta blockers or ACE inhibitors)

SIDE EFFECTS & ADVERSE EFFECTS

• Hyperkalemia
• Hyperchloremic metabolic acidosis
• Acute renal stone
• Kidney stone

DRUG INTERACTION

• Digoxin or sotalol when co-prescribed with Amiloride, can cause severe hypokalemia and increase toxicity of digoxin and sotalol.
• Amiloride can cause hyperkalemia if used with ACEI or sartans in patients with renal impairment.
• Trimethoprim can increase the loss of sodium when given with Amiloride
• K-supplements or K- containing compounds can result in severe and even life threatening hyperkalemia hen given or taken with Amiloride.
• Total parental nutrition given with Amiloride cause metabolic acidosis
• Minor interaction occurs when Amiloride given with cimetidine

NURSING IMPLICATIONS AND CONSIDERATIONS

• Dose should be given in early timings because of increase urination.
• Obtain complete health history (Electrolyte balance & renal function)
• Obtain vital signs with the baseline values specially Blood pressure
• Find out patient’s medication history including alcohol and nicotine consumption to avoid drug interaction
• Determine possible drug allergies of patient.
• Obtain blood and urine specimen for laboratory analysis
• Observe for any change in consciousness, dizziness, fatigue, postural hypotension
• Monitor for fluid intake by measuring intake, output and daily weight.
• Monitor laboratory values specially potassium and sodium levels, BUN, Serum Uric acid.

PATIENT EDUCATION

• Reduce dietary intake of potassium or potassium supplements or ask HP
• Do not breast feed while taking the medicine
• Take medicine with meal to avoid gastric problems
• Explain the right use of medicine with dosage
• Report any visible s/s of proximal edema, SOB, potential sign of Heart Failure or Pulmonary edema
• Report immediate if feeling dizzy or change in consciousness
• Advise them to change position slowly to avoid postural hypotension
• Monitor BP as specified by the HP
• Mention possible side effects that can cause by the use of diuretics such as dry mouth, increase in urination.
• Ask health care professional before taking any vitamin/minerals or other supplements
• When outdoor, wear dark glasses or light color clothe because some diuretics cause photosensitivity.