Aldazide (Hydroflumethiazide,Spironolactone)

Congestive cardiac failure.

Administration of Aldactide once daily with a meal is recommended.

Posology

Adults

Most patients will require an initial dosage of 100 mg spironolactone daily. The dosage should be adjusted as necessary and may range from 25 mg to 200 mg spironolactone daily.

Elderly

It is recommended that treatment is started with the lowest dose and titrated upwards as required to achieve maximum benefit. Care should be taken with severe hepatic and renal impairment which may alter drug metabolism and excretion.

Paediatric population

Although clinical trials using Aldactide have not been carried out in children, as a guide, a daily dosage providing 1.5 mg to 3 mg of spironolactone per kilogram body weight given in divided doses, may be employed.

Aldactide is contraindicated in patients with anuria, acute renal insufficiency, rapidly deteriorating or severe impairment of renal function, hyperkalaemia, significant hypercalcaemia or Addison's disease.

Aldactide should not be administered with other potassium conserving diuretics and potassium supplements should not be given routinely with Aldactide as hyperkalaemia may be induced.

Concomitant use of Aldactide with other potassium-sparing diuretics, angiotensin-converting enzyme (ACE) inhibitors, nonsteroidal anti-inflammatory drugs, angiotensin II antagonists, aldosterone blockers, heparin, low molecular weight heparin or other drugs or conditions known to cause hyperkalaemia, potassium supplements, a diet rich in potassium or salt substitutes containing potassium, may lead to severe hyperkalaemia.

Sulfonamide derivatives including thiazides have been reported to exacerbate or activate systemic lupus erythematosus.

Fluid and electrolyte balance: Fluid and electrolyte status should be regularly monitored particularly in the elderly, in those with significant renal and hepatic impairment, and in patients receiving digoxin and drugs with pro-arrhythmic effects.

Hyperkalaemia may occur in patients with impaired renal function or excessive potassium intake and can cause cardiac irregularities which may be fatal. Should hyperkalaemia develop Aldactide should be discontinued, and if necessary, active measures taken to reduce the serum potassium to normal.

Hypokalaemia may develop as a result of profound diuresis, particularly when Aldactide is used concomitantly with loop diuretics, glucocorticoids or Adrenocorticotropic Hormone.

Hyponatraemia may be induced especially when Aldactide is administered in combination with other diuretics.

Monitor serum potassium levels when using concomitantly with other drugs known to increase the risk of hypokalaemia induced by thiazide diuretics.

Hepatic impairment: Caution should be observed in patients with acute or severe liver impairment as vigorous diuretic therapy may precipitate encephalopathy in susceptible patients. Regular estimation of serum electrolytes is essential in such patients.

Reversible hyperchloraemic metabolic acidosis usually in association with hyperkalaemia has been reported to occur in some patients with decompensated hepatic cirrhosis, even in the presence of normal renal function.

Urea and uric acid: Reversible increases in blood urea have been reported, particularly accompanying vigorous diuresis or in the presence of impaired renal function.

Thiazides may cause hyperuricaemia and precipitate attacks of gout in some patients.

Diabetes mellitus: Thiazides may aggravate existing diabetes and the insulin requirements may alter. Diabetes mellitus which has been latent may become manifest during thiazide administration.

Hyperlipidaemia: Caution should be observed as thiazides may raise serum lipids.

Acute Myopia and Secondary Angle-Closure Glaucoma: Hydrochlorothiazide, a sulfonamide, can cause an idiosyncratic reaction, resulting in acute transient myopia and acute angle-closure glaucoma. Symptoms include acute onset of decreased visual acuity or ocular pain and typically occur within hours to weeks of drug initiation. Untreated acute angle-closure glaucoma can lead to permanent vision loss. The primary treatment is to discontinue hydrochlorothiazide as rapidly as possible. Prompt medical or surgical treatments may need to be considered if the intraocular pressure remains uncontrolled. Risk factors for developing acute angle-closure glaucoma may include a history of sulfonamide or penicillin allergy.

Somnolence and dizziness have been reported to occur in some patients. Caution is advised when driving or operating machinery until the response to initial treatment has been determined.

The following adverse events have been reported in association with spironolactone/ thiazide therapy:

Neoplasms benign, malignant and unspecified (including cysts and polyps): Benign breast neoplasm

Blood and lymphatic system disorders: Leukopenia, agranulocytosis, thrombocytopenia, blood dyscrasias, aplastic anaemia

Immune system disorders: Anaphylactoid reaction

Metabolism and nutrition disorders: Electrolyte imbalance, hyperkalaemia, hypercalcaemia

Psychiatric disorders: Libido disorder, confusional state, restlessness

Nervous system disorders: Dizziness, headache, paraesthesia

Eye disorders: Xanthopsia, acute myopia, acute angle closure glaucoma

Ear and labyrinth disorders: Vertigo

Vascular disorders: Orthostatic hypotension, necrotising vasculitis

Gastrointestinal disorders: Gastrointestinal disorder, nausea, pancreatitis

Hepatobiliary disorders: Abnormal hepatic function, jaundice

Skin and subcutaneous tissue disorders: Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug rash with eosinophilia and systemic symptoms (DRESS), alopecia, hypertrichosis, photosensitivity reaction, pruritis, rash, urticaria, purpura

Musculoskeletal and connective tissue disorders: Muscle spasms, systemic lupus erythematosus

Renal and urinary disorders: Acute renal failure

Reproductive system and breast disorders: Menstrual disorders, gynaecomastia, breast enlargement, breast pain, erectile dysfunction

General disorders and administration site conditions: Malaise, weakness

Investigations: Raised serum lipids

Gynaecomastia may develop in association with the use of spironolactone. Development appears to be related to both dosage level and duration of therapy and is normally reversible when the drug is discontinued. In rare instances some breast enlargement may persist.

Sulfonamide derivatives including thiazides have been reported to exacerbate or activate systemic lupus erythematosus.

Rarely hypercalcaemia has been reported in association with thiazides, usually in patients with pre-existing metabolic bone disease or parathyroid dysfunction.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at www.mhra.gov.uk/yellowcard.

Acute overdosage may be manifested by drowsiness, mental confusion, nausea, vomiting, dizziness or diarrhoea. Hyponatraemia, Hypokalaemia or hyperkalaemia may be induced or hepatic coma may be precipitated in patients with severe liver disease, but these effects are unlikely to be associated with acute overdosage. Symptoms of hyperkalaemia may manifest as paraesthesia, weakness, flaccid paralysis or muscle spasm and may be difficult to distinguish clinically from hypokalaemia. Electro-cardiographic changes are the earliest specific signs of potassium disturbances. No specific antidote has been identified. Improvement may be expected after withdrawal of the drug. General supportive measures including replacement of fluids and electrolytes may be indicated. For hyperkalaemia, reduce potassium intake, administer potassium-excreting diuretics, intravenous glucose with regular insulin or oral ion-exchange resins.

Pharmacotherapeutic group: low-ceiling diuretic, ATC code: C03AA02

Pharmacotherapeutic group: potassium-sparing agents, ATC code C03DA01

Spironolactone, as a competitive aldosterone antagonist, increases sodium excretion whilst reducing potassium loss at the distal renal tubule. It has a gradual and prolonged action.

Hydroflumethiazide is a thiazide diuretic. Diuresis is initiated usually within 2 hours and lasts for about 12-18 hours.

Mechanism of action: Spironolactone/hydroflumethiazide is a combination of two diuretic agents with different but complementary mechanisms and sites of action, thereby providing additive diuretic and antihypertensive effects. Additionally, the spironolactone component helps to minimize the potassium loss characteristically induced by the thiazide component.

The diuretic effect of spironolactone is mediated through its action as a specific pharmacologic antagonist of aldosterone, primarily by competitive binding to receptors at the aldosterone-dependent sodium-potassium exchange site in the distal convoluted renal tubule.

No pharmacokinetic studies have been performed on spironolactone/ hydroflumethiazide. Pharmacokinetic studies have been performed on the individual component of spironolactone and hydroflumethiazide.

Absorption

Spironolactone

Following oral administration of 500 mg tritiated spironolactone in five healthy male volunteers (fasting state), the total radioactivity in plasma reached a peak between 25 and 40 minutes. Although the absolute bioavailability of spironolactone was not determined, the extent of absorption was estimated to be 75%, as 53% of the dose was excreted in the urine during 6 days and approximately 20% in the bile.

Following oral administration of 100 mg of spironolactone daily for 15 days in non-fasted healthy volunteers, time to peak plasma concentration (t_max) and peak plasma concentration (C_max) were 2.6 hr. and 80 ng/ml, respectively. For the 7-alpha-(thiomethyl) spironolactone and canrenone metabolites, t_max values were 3.2 hr. and 4.3 hr., respectively; C_max values were 391 ng/ml and 181 ng/ml, respectively.

Administration with food resulted in higher exposure compared to fasted conditions. Following a single oral dose of 200 mg spironolactone to four healthy volunteers, the mean (± SD) AUC (0 to 24 hours) of the parent drug increased from 288 ± 138 (empty stomach) to 493 ± 105 ng ∙ ml^-1 ∙ hr (with food) (p <0.001).

Hydroflumethiazide

Hydroflumethiazide is incompletely but fairly rapidly absorbed from the gastro-intestinal tract.

Distribution

Spironolactone

Approximately 90% of spironolactone was protein bound based on equilibrium dialysis.

Hydroflumethiazide

No pharmacokinetic studies have been performed with hydroflumethiazide in protein binding.

Biotransformation

Spironolactone

Spironolactone is metabolized by both the kidneys and liver. Following deacetylation and S-methylation, spironolactone is converted to 7-α-thiomethylspironolactone, a sulfur-containing active metabolite that is considered the major metabolite of spironolactone in serum. Approximately 30% of spironolactone is also converted to canrenone by dethioacetylation (non-sulfur containing active metabolite).

Hydroflumethiazide

No pharmacokinetic studies have been performed with hydroflumethiazide in biotransformation.

Elimination

Spironolactone

Elimination of metabolites occurs primarily in the urine and secondarily through biliary excretion in the faeces.

In one pharmacokinetic study in five healthy male volunteers receiving 500 mg of spironolactone, 53% (range: 47% to 57%) of the dose was excreted in the urine within 6 days and the remaining amount could be detected in the faeces (total recovery 90%). In another study of five healthy men, a single dose of spironolactone 200 mg (with radioactive tracer) was administered and in 5 days, 31.6% ± 5.87% of the radioactivity was excreted in the urine mainly as metabolites and 22.7% ± 14.1% in the faeces.

Following oral administration of 100 mg of spironolactone daily for 15 days in non-fasted healthy volunteers, elimination half-life (t_1/2) value for spironolactone was 1.4 hr. For the 7-alpha-(thiomethyl) spironolactone and canrenone metabolites, t_1/2 values were 13.8 hr. and 16.5 hr., respectively.

The renal action of a single dose of spironolactone reaches its peak after 7 hours, and activity persists for at least 24 hours

Hydroflumethiazide

After oral absorption, hydroflumethiazide appears to have a biphasic biological half-life with an estimated alpha-phase of about 2 hours and an estimated beta-phase of about 17 hours; it has a metabolite with a longer half-life, which is extensively bound to the red blood cells. Hydroflumethiazide is excreted in the urine; its metabolite has also been detected in the urine.

Special Populations

No pharmacokinetic studies have been performed with spironolactone/hydroflumethiazide in the elderly or paediatric population or in patients with hepatic or renal insufficiency.

Spironolactone

Orally administered spironolactone has been shown to be a tumorigen in dietary administration studies performed in Sprague Dawley rats, with its proliferative effects manifested on endocrine organs and the liver. In an 18-month study using doses of about 50, 150 and 500 mg/kg/day, there were statistically significant increases in benign adenomas of the thyroid and testes and, in male rats, a dose-related increase in proliferative changes in the liver (including hepatocytomegaly and hyperplastic nodules). In a 24-month study using doses of about 10, 30, and 100 mg/kg/day, the range of proliferative effects included significant increases in hepatocellular adenomas and testicular interstitial cell tumors in males, and significant increases in thyroid follicular cell adenomas and carcinomas in both sexes. There was also a statistically significant, but not dose-related, increase in benign uterine endometrial stromal polyps in females.

In a 12-month study dietary study in rats with potassium canrenoate (a compound chemically similar to spironolactone and whose primary metabolite, canrenone, is also a major product of spironolactone in man) a dose-related (above 30 mg/kg/day) incidence of myelocytic leukemia was observed for a period of 1 year. In 2 year studies in rats, oral administration of potassium canrenoate was associated with myelocytic leukemia and hepatic, thyroid, testicular and mammary tumors.

Neither spironolactone nor potassium canrenoate produced mutagenic effects in tests using bacteria or yeast. In the absence of metabolic activation, neither spironolactone nor potassium canrenoate has been shown to be mutagenic in mammalian tests in vitro. In the presence of metabolic activation, spironolactone and canrenoate have been found to be mutagenic, inconclusive or negative in mammalian tests in vitro. In vivo, neither spironolactone nor potassium canrenoate were found to be genotoxic.

Spironolactone has known endocrine effects in animals including progestational and antiandrogenic effects. In a continuous breeding study there was a small increase in incidence of stillborn pups but no effects on mating and fertility at 500 mg spironolactone /kg/day. In female rats treatment with spironolactone for 7 days (100 mg/kg i.p), was found to increase the length of the estrous cycle by prolonging diestrus during treatment and inducing constant diestrus during a 2-week post-treatment observation period due to retarded ovarian follicle development and a reduction in circulating oestrogen levels. In female mice spironolactone dosed i.p, caused a decrease in the number of mated mice that conceived and a decreased in the number of implanted embryos in those that became pregnant at doses of 100 mg/kg/day and also increased the latency period to mating at 200 mg/kg. These effects are associated with an inhibition of ovulation and implantation.

No teratogenic or other embryo-toxic effects were observed in mice at doses up to 20 mg/kg however, this dose caused an increased rate of resorption and a lower number of live foetuses in rabbits. On a body surface area basis, 20 mg/kg is either substantially below or approximate to the maximum recommended human dose in mice and rabbits respectively. Because of its anti-androgenic activity and the requirement of testosterone for male morphogenesis, spironolactone may have the potential for adversely affecting sex differentiation of the male during embryogenesis. Following administration of 200 mg/kg/day in rats on gestation Days 13 to 21, feminization of male foetuses was observed. Dose dependent changes to the reproductive tract which persisted into adulthood including decreases in weights of the ventral prostate and seminal vesicle in males, increased ovary and uterus weights in females, and other indications of endocrine dysfunction were seen in offspring exposed to Spironolactone during late pregnancy at 50 and 100 mg/kg/day.

None stated.

No special requirements for disposal. Any unused medicinal product or waste material should be disposed of in accordance with local requirements.