Aldactone (Spironolakton). Dosage, Side Effects, Interactions
Aldactone (Spironolactone) belongs to the group of potassium-sparing diuretics and is used for the treatment of high blood pressure in primary hyperaldosteronism and for the treatment of edema and ascites in secondary hyperaldosteronism. Spironolactone and its analogues are structurally similar to aldosterone.
The potassium-sparing diuretic spironolactone is used for:
- Primary hyperaldosteronism unless surgery is indicated
- Edema and/or ascites in diseases associated with secondary hyperaldosteronism
- Nephrotic Syndrome
How Aldactone (Spironolactone) works
The diuretic spironolactone competitively blocks the binding of aldosterone to its cytoplasmic receptor in the late distal tubule and collecting duct, preventing aldosterone from entering the nucleus via its receptor and preventing the synthesis of aldosterone-induced proteins. The essential aldosterone effects such as sodium reabsorption and potassium secretion are suppressed in this way. Only in extremely high doses does spironolactone inhibit the biosynthesis of aldosterone.
Other effects of spironolactone are:
- increase in sodium and chloride excretion and, to a lesser extent, in calcium excretion;
- Reduction of potassium and ammonium excretion
- Reduction of renal magnesium excretion
- Decrease in glomerular filtration rate
- Increase in serum urea concentrations
Clinical onset of effect is gradual with continuous dosing, peaking at 2 to 3 days or later; if necessary, the maximum diuretic effect can only occur after 2 weeks.
- About 73% of spironolactone is rapidly absorbed after oral administration.
- Spironolactone absorption increases when taken with food.
- Depending on the method, the plasma protein binding of spironolactone is 90% (equilibrium dialysis) or 98% (ultrafiltration).
When administered orally, spironolactone is subject to a pronounced first-pass effect and is mainly metabolised in the liver and kidneys to:
- canrenone or canrenoate
- 7-α-thiomethylspirolactone and 6-β-hydroxy-7-α-thiomethylspirolactone, respectively
Maximum plasma concentrations of spironolactone are reached 1-2 hours after oral administration and maximum plasma concentrations of the metabolites are measured after about 2-3 hours.
- Excretion is predominantly renal and to a lesser extent via the bile.
- The proportion of unchanged spironolactone is low. Only metabolites are found in the urine, mainly canrenone and its glucuronide ester and 6-β-hydroxysulfoxide.
- The elimination half-life for spironolactone after oral administration is 1-2 hours, while the metabolites are eliminated more slowly.
- The terminal elimination half-lives are about 20 hours for canrenone, about 3 hours for 7-α-thiomethylspirolactone and about 10 hours for 6-β-hydroxy7-α-thiomethylspirolactone.
Dosage of Aldactone (Spironolactone)
The dosage of spironolactone should be determined depending on the severity and extent of the disease. A starting dose of 100-200 mg spironolactone per day is recommended for adults . If the effectiveness is insufficient, the daily dose can be increased to a maximum of 400 mg spironolactone per day.
As a maintenance dose , 50-100 mg spironolactone up to a maximum of 100-200 mg spironolactone are usually sufficient. The maintenance dose can be administered daily, every 2nd or every 3rd day as required.
Side effects of Aldactone (Spironolactone)
Common side effects associated with spironolactone therapy include:
- Life-threatening hyperkalemia (particularly in the case of impaired renal function): hyperkalemic paralysis (muscle paralysis) and cardiac arrhythmia possible
- Hyperuricemia (can lead to gout attacks in predisposed patients)
- usually reversible gynecomastia (depending on the dose level and duration of treatment)
- increased tenderness of the nipples and breast tenderness
The following medicines must not be used during spironolactone therapy:
- Potassium-sparing diuretics ( amiloride , triamterene )
The following drugs should not be used during spironolactone therapy:
- Potassium -containing preparations (e.g. potassium chloride )
- ACE inhibitors (eg, captopril , enalapril )
- angiotensin II antagonists
- Aldosterone Receptor Antagonists
- Heparin , low molecular weight heparins
- Nonsteroidal anti-inflammatory drugs (e.g. acetylsalicylic acid , indomethacin )
- Trimethoprim / Sulfamethoxazole ( Co-trimoxazole )
- Other drugs that cause hyperkalemia
There is a risk of hyperkalemia when taken with the following compounds:
- Furosemide : acute renal failure possible
- Blood pressure lowering medicines
- norepinephrine and adrenaline
- other diuretics
Spironolactone must not be used with:
- Hypersensitivity to the active substance
- acute renal failure
- Severe renal insufficiency with oliguria or anuria (creatinine clearance below 30 ml/min per 1.73 m 2 body surface area and/or serum creatinine above 1.8 mg/dl)
- Addison’s disease or other disorders associated with hyperkalemia
- concomitant use of eplerenone or other potassium-sparing diuretics
- hypovolemia or dehydration
Spironolactone must not be used during pregnancy and lactation and is contraindicated here. Animal studies have shown feminization of the genitals of male offspring and evidence of endocrine disorders in female and male offspring. Antiandrogenic effects have been demonstrated in humans.
The pharmacologically active metabolite canrenoate is excreted in human milk (milk-to-plasma concentration ratio 0.7). Therefore, spironolactone is also contraindicated during lactation. If treatment is required, breastfeeding must be stopped.
Drowsiness and drowsiness are possible with the use of spironolactone. Particular care should therefore be taken when driving a car or using machines, especially at the beginning of treatment, until the patient knows his reaction to spironolactone.
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