Spironolactone

Spironolactone

[1 tablet 22 cents]

ADMINISTRATION ROUTES:

• PO

ALTERNATIVE NAMES:

• Spirotone, spironolactone

ICU INDICATIONS:

1. heart failure
2. essential hypertension
3. fluid overload

PRESENTATION AND ADMINISTRATION:

• PO:
  Tablets: Spirotone 25mg and 100mg tablets (pale orange)
  Oral Liquid: Spironolactone oral liquid 5mg/ml
  Note: crush tablets for NG administration.

DOSAGE:

• PO:
  Initially 25-100mg/day in single or divided doses; increase to maximum of 200mg/day as required.

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

• Dose in renal impairment [GFR (ml/min)]:
  <10: Avoid
  10-30: Avoid
  >30-50: Avoid
• Dose in renal replacement therapy:
  CAPD: Avoid
  HD: Avoid
  CVVHDF: 25mg per day

DOSAGE IN PAEDIATRICS:

• PO (NOT/kg):
  1-10kg: 6.25mg 12 hourly
  11-20kg: 12.5mg 12 hourly
  21-40kg: 25mg 12 hourly
  >40kg: 25mg 8 hourly

CLINICAL PHARMACOLOGY:

• Spironolactone is a potassium sparing diuretic.

CONTRAINDICATIONS:

1. hyperkalaemia
2. renal failure

WARNINGS

• Hyperkalaemia:
  Excessive potassium intake may cause hyperkalemia in patients receiving spironolactone

PRECAUTIONS

• General:
  See WARNINGS
• Laboratory Tests: No tests are required in addition to routine ICU tests; close monitoring of potassium and renal function are important
• Drug/Laboratory Test Interactions:
  Several reports of possible interference with digoxin radioimmunoassays by spironolactone, or its metabolites, have appeared in the literature. Neither the extent nor the potential clinical significance of its interference (which may be assay-specific) has been fully established.

IMPORTANT DRUG INTERACTIONS FOR THE ICU

• ACE Inhibitors:
  Concomitant administration of ACE inhibitors with potassium-sparing diuretics has been associated with severe hyperkalemia.
• Skeletal Muscle Relaxants, Nondepolarizing:
  Possible increased responsiveness to the muscle relaxant may result.
• Lithium:
  Lithium generally should not be given with diuretics. Diuretic agents reduce the renal clearance of lithium and add a high risk of lithium toxicity.
• Nonsteroidal Anti-inflammatory Drugs (NSAIDs):
  In some patients, the administration of an NSAID can reduce the diuretic, natriuretic, and antihypertensive effect of loop, potassium-sparing and thiazide diuretics. Combination of NSAIDs, has been associated with severe hyperkalemia.
  
• Digoxin:
  Spironolactone has been shown to increase the half-life of digoxin. This may result in increased serum digoxin levels and subsequent digitalis toxicity.

ADVERSE REACTIONS

• Digestive: Gastric bleeding, ulceration, gastritis, diarrhea and cramping, nausea, vomiting.
• Endocrine: Gynecomastia, irregular menses or amenorrhea, postmenopausal bleeding.
• Haematologic: Agranulocytosis.
• Hypersensitivity: Fever, urticaria, maculopapular or erythematous cutaneous eruptions, anaphylactic reactions, vasculitis.
• Nervous System/Psychiatric: Mental confusion, ataxia, headache, drowsiness, lethargy.
• Liver/Biliary: A very few cases of mixed cholestatic/hepatocellular toxicity, with 1 reported fatality, have been reported with spironolactone administration.