spironolactone

CLINICAL USE

Diuretic, aldosterone antagonist

DOSE IN NORMAL RENAL FUNCTION

25–400 mg daily

PHARMACOKINETICS

Molecular weight :416.6

%Protein binding :90

%Excreted unchanged in urine : 0 (47–57 as metabolites)

Volume of distribution (L/kg) :No data

half-life – normal/ESRD (hrs) :1.3–1.4/Unchanged

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

20 to 50 : 50% of normal dose

10 to 20 : 50% of normal dose

<10 : Use with caution

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD :Not dialysed. Dose as in GFR <10 mL/min

HD :Not dialysed. Dose as in GFR <10 mL/min

HDF/high flux :Unknown dialysability. Dose as in GFR <10 mL/min

CAV/VVHD :Not dialysed. Dose as in GFR 10 to 20 mL/min

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugsACE inhibitors or angiotensin-II antagonists: enhanced hypotensive effect; risk of severe hyperkalaemia

Antibacterials: avoid concomitant use with lymecycline

Antidepressants: increased risk of postural hypotension with tricyclics
Antihypertensives: enhanced hypotensive effect; increased risk of first dose hypotensive effect with post-synaptic alpha-blockersCardiac glycosides: increased digoxin concentration; possibly increased digitoxin concentration

Ciclosporin: increased risk of hyperkalaemia

Lithium: reduced lithium excretion NSAIDs: increased risk of hyperkalaemia (especially with indometacin); increased risk of nephrotoxicity; diuretic effect of spironolactone antagonised by aspirin

Potassium salts: increased risk of hyperkalaemia

Tacrolimus: increased risk of hyperkalaemia

ADMINISTRATION

Reconstition

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Route

Oral

Rate of Administration

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Comments

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OTHER INFORMATION

Renal patients are at an increased risk of hyperkalaemia and therefore spironolactone should be used with caution. It has active metabolites with long half-livesSmall studies have shown that doses of 25 mg of spironolactone 3 times a week can be safely used in haemodialysis patients although unknown whether that dose would be therapeutic – potassium levels should be monitored closely. Another small study used 25 mg daily but the potassium was monitored 3 times a week.

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