Isofer

Uses

Isofer is used for Congestive heart failure, Hepatic cirrhosis with ascites and oedema, Nephrotic syndrome, Primary hyperaldosteronism, Essential hypertension, For the treatment of patients with hypokalemia

Isofer is a long-acting aldosterone antagonist. Isofer is a specific pharmacologic antagonist of aldosterone, acting primarily through competitive binding of receptors at the aldosterone dependent sodium-potassium exchange site in the distal convoluted renal tubule. Isofer causes increased amounts of sodium and water to be excreted, while potassium and magnesium is retained.

Isofer is also used to associated treatment for these conditions: Acne, Ascites, Congestive Heart Failure (CHF), Edema, High Blood Pressure (Hypertension), Hypokalemia, Idiopathic Hirsutism, Nephrotic Syndrome, Primary Hyperaldosteronism, Secondary hyperaldosteronism, Chronic heart failure with reduced ejection fraction (NYHA Class III), Chronic heart failure with reduced ejection fraction (NYHA Class IV), Idiopathic hyperaldosteronism

How Isofer works

Isofer competitively inhibits aldosterone dependant sodium potassium exchange channels in the distal convoluted tubule. This action leads to increased sodium and water excretion, but more potassium retention. The increased excretion of water leads to diuretic and also antihypertensive effects.

Dosage

Isofer dosage

Edema in adults (congestive heart failure, hepatic cirrhosis, or nephrotic syndrome): An initial daily dosage of 100 mg of Isofer administered in either single or divided doses is recommended, but may range from 25 to 200 mg daily. Combined therapy with other diuretics is indicated when more rapid diuresis is desired.

Primary hyperaldosteronism: After the diagnosis of hyperaldosteronism has been established, Isofer may be administered in doses of 100 to 400 mg daily in preparation for surgery. For patients who are considered unsuitable for surgery, Isofer may be employed for long-term maintenance therapy at the lowest effective dosage determined for the individual patient.

Essential hypertension: For adults, an initial daily dosage of 50 to 100 mg of Isofer administered in either single or divided doses is recommended.

Hypokalemia: Isofer in a dosage ranging from 25 mg to 100 mg daily is useful in treating a diuretic-induced hypokalemia.

Side Effects

Gynaecomastia may develop in association with the use of Isofer. Other adverse reactions are: GI symptoms including cramping and diarrhoea, drowsiness, lethargy, headache, urticaria, mental confusion, impotence, irregular menses or amenorrhoea and post-menopausal bleeding.

Toxicity

Patients experiencing an overdose may present with drowsiness, mental confusion, maculopapular or erythematous rash, nausea, vomiting, dizziness, or diarrhea. Vomiting is generally induced or a gastric lavage is performed. Supportive treatment involves maintining hydration, electrolyte balance, and vital functions.

The oral LD50 in mice, rats, and rabbits is >1g/kg.

Isofer should be avoided in pregnancy due to reports of feminization of male fetuses in animal studies. Active metabolites of spironolactone are present in breast milk and levels that are likely inconsequential, though the long term effects have not been studied.

In animal studies, spironolactone slowed follicle development, ovulation, and implantation. Isofer increased the incidence of benign adenomas in the testes of male rats, benign uterine endometrial stromal polyps in female rats, and thyroid follicular cell adenomas in both sexes of rats. Isofer and canrenone are generally not considered to be mutagenic in tests but canrenone occasionally tests positive for mutagenicity with metabolic activation and spironolactone has occasionally tested inconclusive though slightly positive for mutagenicity.

Precaution

All patients receiving diuretic therapy should be observed for evidence of fluid or electrolyte imbalance. Hyperkalemia may occur in patients with impaired renal function or excessive potassium intake and can cause cardiac irregularities, which may be fatal.

Interaction

ACE inhibitors: Concomitant administration of ACE inhibitors with potassium-sparing diuretics has been associated with severe hyperkalemia.

Alcohol, barbiturates, or narcotics: Potentiation of orthostatic hypotension may occur.

Corticosteroids, ACTH: Intensified electrolyte depletion, particularly hypokalemia, may occur.

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.

Digoxin: Isofer has been shown to increase the half-life of digoxin.

Food Interaction

• Avoid alcohol.
• Avoid potassium-containing products. Potassium products increase the risk of hyperkalemia.
• Take with or without food. Food increases the bioavailability of spironolactone by nearly 100%. It should be taken at a consistent time in regards to food.

Isofer Alcohol interaction

[Moderate]

Many psychotherapeutic and CNS-active agents (e.g., anxiolytics, sedatives, hypnotics, antidepressants, antipsychotics, opioids, alcohol, muscle relaxants) exhibit hypotensive effects, especially during initiation of therapy and dose escalation.

Coadministration with antihypertensives and other hypotensive agents, in particular vasodilators and alpha-blockers, may result in additive effects on blood pressure and orthostasis.

Caution and close monitoring for development of hypotension is advised during coadministration of these agents.

Some authorities recommend avoiding alcohol in patients receiving vasodilating antihypertensive drugs.

Patients should be advised to avoid rising abruptly from a sitting or recumbent position and to notify their physician if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia.

Isofer Drug Interaction

Major: sacubitril / valsartanModerate: duloxetine, apixaban, metoprolol, metoprolol, alprazolamMinor: aspirin, aspirinUnknown: omega-3 polyunsaturated fatty acids, furosemide, atorvastatin, pregabalin, clopidogrel, montelukast, levothyroxine, acetaminophen, cyanocobalamin, ascorbic acid, cholecalciferol, cetirizine

Isofer Disease Interaction

Major: acidosis, diabetes, electrolytes/fluid, hyperkalemia, liver disease, renal dysfunctionModerate: hyperuricemia

Volume of Distribution

Volume of distribution data is not readily available.

Elimination Route

Isofer reaches a maximum concentration in 2.6 hours and an active metabolite (canrenone) reaches a maximum concentration in 4.3 hours. When taken with food, the bioavailability of spironolactone increases to 95.4%.

Giving spironolactone with food increases the maximum concentration from 209ng/mL to 301ng/mL. The time to maximum concentration also increases from 2.28 hours to 3.05 hours. The area under the curve varies from 2103ng/mL*hr to 4544ng/mL*hr.

Half Life

1.4 hours.

Canrenone has a half life of 16.5 hours, 7-α-thiomethylspirolactone has a half life of 13.8 hours, and 6-ß-hydroxy-7-α-thiomethylspirolactone has a half life of 15 hours.

Clearance

Clearance data is not readily available.

Elimination Route

Metabolites of spironolactone are excreted 42-56% in urine, and 14.2-14.6% in the feces. No unmetabolized spironolactone is present in the urine.

Pregnancy & Breastfeeding use

Pregnancy: Isofer should not be used during pregnancy

Lactation: Canrenone, an active metabolite of Isofer, appears in breast milk. If use of the drug is deemed essential an alternative method of infant feeding should be instituted.

Contraindication

Isofer is contraindicated in patients with acute renal insufficiency, significant impairment of renal function, anuria, hyperkalaemia or sensitivity to Isofer.

Acute Overdose

Symptoms of overdosage include drowsiness, mental confusion, dizziness, diarrhea and vomiting etc. Patients should induce vomiting or evacuate the stomach by lavage during Isofer overdoasge.

Storage Condition

Store in a cool and dry place protected from light. Keep out of reach of children.

Innovators Monograph

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