Spironolactone, sold under the brand name Aldactone among others, is a medication that is primarily used to treat fluid build-up due to heart failure, liver scarring, or kidney disease. It is also used in the treatment of high blood pressure, low blood potassium that does not improve with supplementation, early puberty in boys, acne and excessive hair growth in women, and as a part of feminizing hormone therapy in transgender women. Spironolactone is taken by mouth.
Common side effects include electrolyte abnormalities, particularly high blood potassium, nausea, vomiting, headache, rashes, and a decreased desire for sex. In those with liver or kidney problems, extra care should be taken. Spironolactone has not been well studied in pregnancy and should not be used to treat high blood pressure of pregnancy. It is a steroid that blocks the effects of the hormones aldosterone and testosterone and has some estrogen-like effects. Spironolactone belongs to a class of medications known as potassium-sparing diuretics.
Spironolactone was discovered in 1957 and was introduced in 1959. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. It is available as a generic medication. The wholesale cost in the developing world as of 2014 is between US$0.02 and US$0.12 per day. In the United States it costs about US$0.50 per day.
Video Spironolactone
Medical uses
Spironolactone is used primarily to treat heart failure, edematous conditions such as nephrotic syndrome or ascites in people with liver disease, essential hypertension, low blood levels of potassium, secondary hyperaldosteronism (such as occurs with liver cirrhosis), and Conn's syndrome (primary hyperaldosteronism). The most common use of spironolactone is in the treatment of heart failure. On its own, spironolactone is only a weak diuretic because it primarily targets the distal nephron (collecting tubule), where only small amounts of sodium are reabsorbed, but it can be combined with other diuretics to increase efficacy. The classification of spironolactone as a "potassium-sparing diuretic" has been described as obsolete.
Spironolactone has antiandrogenic activity. For this reason, it is frequently used to treat a variety of dermatological conditions in which androgens play a role. Some of these uses include acne, seborrhea, hirsutism, and pattern hair loss in women. Spironolactone is the most commonly used medication in the treatment of hirsutism in the United States. High doses of spironolactone, which are needed for considerable antiandrogenic effects, are not recommended in men due to the high risk of feminization and other side effects. Spironolactone is also commonly used to treat symptoms of hyperandrogenism, such as due to polycystic ovary syndrome, in women. The medication is not approved for use as an antiandrogen by the Food and Drug Administration; instead, it is used off-label for such purposes.
Heart failure
While loop diuretics remain first-line for most people with heart failure, spironolactone has shown to reduce both morbidity and mortality in numerous studies and remains an important agent for treating fluid retention, edema, and symptoms of heart failure. Current recommendations from the American Heart Association are to use spironolactone in patients with NYHA Class II-IV heart failure who have a left ventricular ejection fraction of less than 35%.
In a randomized evaluation which studied people with severe congestive heart failure, people treated with spironolactone were found to have a relative risk of death of 0.70 or an overall 30% relative risk reduction compared to the placebo group, indicating a significant death and morbidity benefit of the medication. People in the study's intervention arm also had fewer symptoms of heart failure and were hospitalized less frequently. Likewise, it has shown benefit for and is recommended in patients who recently suffered a heart attack and have an ejection fraction less than 40%, who develop symptoms consistent with heart failure, or have a history of diabetes mellitus. Spironolactone should be considered a good add-on agent, particularly in those patients "not" yet optimized on ACE inhibitors and beta-blockers. Of note, a recent randomized, double-blinded study of spironolactone in patients with symptomatic heart failure with "preserved" ejection fraction (i.e. >45%) found no reduction in death from cardiovascular events, aborted cardiac arrest, or hospitalizations when spironolactone was compared to placebo.
It is recommended that alternatives to spironolactone be considered if serum creatinine is greater than 2.5 mg/dL (221 µmol/L) in males or greater than 2 mg/dL (176.8 µmol/L) in females, if glomerular filtration rate is below 30 mL/min or with a serum potassium of greater than 5.0 mEq/L given the potential for adverse events detailed elsewhere in this article. Doses should be adjusted according to the degree of kidney function as well.
According to systematic review, in heart failure with preserved ejection fraction, treatment with spironolactone did not improve patient outcomes. This is based on the TOPCAT Trial examining this issue, which found that of those treated with placebo had a 20.4% incidence of negative outcome vs 18.6% incidence of negative outcome with spironolactone. However, because the p-value of the study was 0.14, and the unadjusted hazard ratio was 0.89 with a 95% confidence interval of 0.77 to 1.04, it is determined the finding had no statistical significance. Hence the finding that patient outcomes are not improved with use of spironolactone. More recently, when blood samples from 366 patients in the TOPCAT study were analyzed for presence of canrenone (an active metabolite of spironolactone), 30% of blood samples from Russia lacked detectable residues of canrenone. This led to the conclusion that the TOPCAT trial results in Russia do not reflect actual clinical experience with spironolactone in patients with preserved ejection fraction. The TOPCAT study results are now considered to have been invalidated. The study's prime investigator and other prominent research cardiologists are now advising physicians treating heart failure with preserved ejection fraction to consider prescribing spironolactone pending outcome of two multicenter trials of newer medications.
Due to its antiandrogenic properties, spironolactone can cause effects associated with low androgen levels and hypogonadism in males. For this reason, men are typically not prescribed spironolactone for any longer than a short period of time, e.g., for an acute exacerbation of heart failure. A newer medication, eplerenone, has been approved by the U.S. Food and Drug Administration for the treatment of heart failure, and lacks the antiandrogenic effects of spironolactone. As such, it is far more suitable for men for whom long-term medication is being chosen. However, eplerenone may not be as effective as spironolactone or the related medication canrenone in reducing mortality from heart failure.
The clinical benefits of spironolactone as a diuretic are typically not seen until 2 to 3 days after dosing begins. Likewise, the maximal antihypertensive effect may not be seen for 2 to 3 weeks.
Unlike with some other diuretics, potassium supplementation should not be administered while taking spironolactone, as this may cause dangerous elevations in serum potassium levels resulting in hyperkalemia and potentially deadly abnormal heart rhythms.
High blood pressure
About 1 in 100 people with hypertension has elevated levels of aldosterone; in these people, the antihypertensive effect of spironolactone may exceed that of complex combined regimens of other antihypertensives since it targets the primary cause of the elevated blood pressure. However, a Cochrane review found adverse effects at high doses and little effect on blood pressure at low doses in the majority of people with high blood pressure. There is no evidence of person-oriented outcome at any dose in this group.
Skin and hair conditions
Androgens like testosterone and DHT play a critical role in the pathogenesis of a number of dermatological conditions including acne, seborrhea, hirsutism (excessive facial/body hair growth in women), and pattern hair loss (androgenic alopecia). In demonstration of this, women with complete androgen insensitivity syndrome (CAIS) do not produce sebum or develop acne and have little to no body, pubic, or axillary hair. Moreover, men with congenital 5?-reductase type II deficiency 5?-reductase being an enzyme that greatly potentiates the androgenic effects of testosterone in the skin, have little to no acne, scanty facial hair, reduced body hair, and reportedly no incidence of male-pattern hair loss. Conversely, hyperandrogenism in women, for instance due to polycystic ovary syndrome (PCOS) or congenital adrenal hyperplasia (CAH), is commonly associated with acne and hirsutism as well as virilization (masculinization) in general. In accordance with the preceding, antiandrogens are highly effective in the treatment of the aforementioned androgen-dependent skin and hair conditions.
Because of the antiandrogenic activity of spironolactone, it can be quite effective in treating acne in women, and also reduces oil that is naturally produced in the skin. Though not the primary intended purpose of the medication, the ability of spironolactone to be helpful with problematic skin and acne conditions was discovered to be one of the beneficial side effects and has been quite successful. Oftentimes, for women treating acne, spironolactone is prescribed and paired with a birth control pill. Positive results in the pairing of these two medications have been observed, although these results may not be seen for up to three months. Spironolactone is commonly used in the treatment of hirsutism in women, and is considered to be a first-line antiandrogen for this indication. Spironolactone can be used in the treatment of female-pattern hair loss (pattern scalp hair loss in women). There is tentative low quality evidence supporting its use for this indication. Although apparently effective, it should be noted that not all cases of female-pattern hair loss are dependent on androgens.
Antiandrogens like spironolactone are male-specific teratogens which can feminize male fetuses due to their antiandrogenic effects. For this reason, it is recommended that antiandrogens only be used to treat women who are of reproductive age in conjunction with adequate contraception. Oral contraceptives, which contain an estrogen and a progestin, are typically used for this purpose. Moreover, oral contraceptives themselves are functional antiandrogens and are independently effective in the treatment of androgen-dependent skin and hair conditions, and hence can significantly augment the effectiveness of antiandrogens in the treatment of such conditions.
Spironolactone is not generally used in men for the treatment of androgen-dependent dermatological conditions because of its feminizing side effects, but it is effective for such indications in men similarly. This is supported by the usefulness of spironolactone as an antiandrogen in transgender women.
Transgender hormone therapy
Spironolactone is frequently used as a component of feminizing hormone therapy in transgender women, especially in the United States (where cyproterone acetate is not available), usually in addition to an estrogen. Other clinical effects include decreased male pattern body hair, the induction of breast development, feminization in general, and lack of spontaneous erections.
Doses and forms
Spironolactone is typically used at a low dosage of 25 to 50 mg/day in the treatment of heart failure, while it is used at low to high dosages of 25 to 200 mg/day in the treatment of essential hypertension, and at high dosages of 100 to 400 mg/day for hyperaldosteronism and ascites due to cirrhosis. The medication is typically used at high dosages of 100 to 200 mg/day in the treatment of skin and hair conditions in women, and at high dosages of 100 to 400 mg/day in feminizing hormone therapy for transgender women.
Spironolactone is available in the form of tablets (25 mg, 50 mg, 100 mg; brand name Aldactone, others) and suspensions (25 mg/5 mL; brand name CaroSpir) for use by mouth. It has also been marketed in the form of 2% and 5% topical cream in Italy for the treatment of acne and hirsutism under the brand name Spiroderm, but this product is no longer available. The medication is also available in combination with other medications, such as hydrochlorothiazide (brand name Aldactazide, others). Spironolactone has poor water solubility, and for this reason, only oral and topical formulations have been developed; other routes of administration such as intravenous injection are not used. The only antimineralocorticoid that is available as a solution for parenteral use is the related medication potassium canrenoate.
Comparison
There are few available options for antiandrogen therapy. Spironolactone, cyproterone acetate, and flutamide are some of the most well-known and widely used medications. Compared to cyproterone acetate, spironolactone is considerably less potent as an antiandrogen by weight and binding affinity to the androgen receptor. However, at the doses at which they are typically used, spironolactone and cyproterone acetate have been found to be roughly equivalent in terms of effectiveness for androgen-related conditions in women, though cyproterone acetate has shown a slight though non-statistically-significant advantage in some studies. Also, it has been suggested that cyproterone acetate could be more effective in situations where androgen levels are more pronounced, though this has not been evaluated.
Flutamide, another frequently used antiandrogen which is nonsteroidal and a pure androgen blocker, though much less potent by weight and binding affinity to the androgen receptor than either spironolactone or cyproterone acetate, has been found to be more effective as an antiandrogen in women than either of them when it is used at the typical treatment doses. However, the uses of both cyproterone acetate and flutamide have been associated with liver toxicity, which can be severe with flutamide and has resulted in cyproterone acetate never being approved in the United States. Bicalutamide is a more potent, safer, and more tolerable alternative to flutamide, but is relatively little-studied in the treatment of androgen-dependent conditions aside from prostate cancer, though it has been used to treat hirsutism. Gonadotropin-releasing hormone (GnRH) analogues are another very effective option for antiandrogen therapy, but have not been widely employed for this purpose due to their high cost and limited insurance coverage despite many now being available as generics. As such, spironolactone may be the only practical, safe, available, and well-supported antiandrogen option in some cases.
In a study of the predictive markers for transgender women requesting breast augmentation, there was a significantly higher rate of those treated with spironolactone requesting breast augmentation compared to other antiandrogens such as cyproterone acetate or GnRH analogues, which was interpreted by the study authors as being potentially indicative that spironolactone may result in poorer breast development in comparison. This may be related to the fact that spironolactone has been regarded as a relatively weak antiandrogen compared to other options.
Maps Spironolactone
Contraindications
Contraindications of spironolactone include hyperkalemia (high potassium levels), severe and end-stage kidney disease (due to high hyperkalemia risk, except possibly in those on dialysis), Addison's disease (adrenal insufficiency and low aldosterone levels), and concomitant use of eplerenone.
Side effects
The most common side effect of spironolactone is urinary frequency. Other general side effects include dehydration, hyponatremia (low sodium levels), mild hypotension (low blood pressure), ataxia (muscle incoordination), drowsiness, dizziness, dry skin, and rashes. Because of its antiandrogenic activity, spironolactone can, in men, cause breast tenderness, gynecomastia (breast development), feminization in general, and demasculinization, as well as sexual dysfunction including loss of libido and erectile dysfunction, although these side effects are usually confined to high doses of spironolactone. At very high doses, spironolactone has also been associated with testicular atrophy and reversibly reduced fertility, including semen abnormalities such as decreased sperm count and motility in men. However, such doses of spironolactone are rarely used clinically. In women, spironolactone can cause menstrual irregularities, breast tenderness, and breast enlargement. Aside from these adverse effects, the side effects of spironolactone in women taking high doses are minimal, and it is well-tolerated.
The most important potential side effect of spironolactone is hyperkalemia (high potassium levels), which, in severe cases, can be life-threatening. Hyperkalemia in these people can present as a non anion-gap metabolic acidosis. Spironolactone may put people at a heightened risk for gastrointestinal issues like nausea, vomiting, diarrhea, cramping, and gastritis. In addition, there has been some evidence suggesting an association between use of the medication and bleeding from the stomach and duodenum, though a causal relationship between the two has not been established. Also, spironolactone is immunosuppressive in the treatment of sarcoidosis.
Increased glucocorticoid activity in the body is associated with depression. As such, it is thought that there may be a risk of depression with spironolactone treatment. A small amount of clinical research supports this notion.
High potassium levels
Spironolactone can cause hyperkalemia, or high blood potassium levels. Rarely, this can be fatal. Of people prescribed typical dosages of spironolactone, 10 to 15% have been found to develop some degree of hyperkalemia, and 6% have been found to develop severe hyperkalemia. At a higher dosage, a rate of hyperkalemia of 24% has been observed. An abrupt and major increase in the rate of hospitalization due to hyperkalemia from 0.2% to 11% and in the rate of death due to hyperkalemia from 0.3 per 1,000 to 2.0 per 1,000 between early 1994 and late 2001 has been attributed to a parallel rise in the number of prescriptions written for spironolactone upon the publication of the Randomized Aldactone Evaluation Study (RALES) in July 1999. The risk of hyperkalemia with spironolactone is greatest in the elderly, in people with renal impairment (e.g., due to chronic kidney disease or diabetic nephropathy), in people taking certain other medications (including ACE inhibitors, angiotensin II receptor blockers, nonsteroidal anti-inflammatory drugs, and potassium supplements), and at higher dosages of spironolactone.
Although spironolactone poses an important risk of hyperkalemia in the elderly, in those with kidney or cardiovascular disease, and/or in those taking medications or supplements which increase circulating potassium levels, a large retrospective study found that the rate of hyperkalemia in young women without such characteristics who had been treated with high doses of spironolactone for dermatological conditions did not differ from that of controls. This suggests that hyperkalemia may not be a significant risk in such individuals, and that routine monitoring of circulating potassium levels may be unnecessary in this population. However, other sources have claimed that hyperkalemia can nonetheless also occur in people with more normal renal function and presumably without such risk factors.
Breast changes
Spironolactone frequently causes breast pain and breast enlargement in women. This is "probably because of estrogenic effects on target tissue." At high doses, breast tenderness is reported to occur in up to 40% of women, while breast enlargement may occur in 26% of women and is described as mild. Some women have considered spironolactone-induced breast enlargement to be a positive effect.
Spironolactone also commonly and dose-dependently produces gynecomastia (breast development) as a side effect in men. At low doses, the rate is only 5 to 10%, but at high doses, up to or exceeding 50% of men may develop gynecomastia. In the RALES, 9.1% of men taking 25 mg/day spironolactone developed gynecomastia, compared to 1.3% of controls. Conversely, in studies of healthy men given high-dose spironolactone, gynecomastia occurred in 3 of 10 (30%) at 100 mg/day, in 5 of 8 (62.5%) at 200 mg/day, and in 6 of 9 (66.7%) at 400 mg/day, relative to none of 12 controls. The severity of gynecomastia with spironolactone varies considerably, but is usually mild. As with breast enlargement caused by spironolactone in women, gynecomastia due to spironolactone in men is often although inconsistently accompanied by breast tenderness. In the RALES, only 1.7% of men developed breast pain, relative to 0.1% of controls.
The time to onset of spironolactone-induced gynecomastia has been found to be 27 ± 20 months at low doses and 9 ± 12 months at high doses. Gynecomastia induced by spironolactone usually regresses after a few weeks following discontinuation of the medication. However, after a sufficient duration of gynecomastia being present (e.g., one year), hyalinization and fibrosis of the tissue occurs and drug-induced gynecomastia may become irreversible.
Menstrual disturbances
In women, menstrual disturbances are common during spironolactone treatment, with 10 to 50% of women experiencing them at moderate doses and almost all experiencing them at a high doses. Most women taking moderate doses of spironolactone develop amenorrhea, and normal menstruation usually returns within two months of discontinuation. Spironolactone produces an irregular, anovulatory pattern of menstrual cycles. It is also associated with metrorrhagia and menorrhagia (or menometrorrhagia) in a large percentage of women. It has no birth control effect. It has been suggested that the weak progestogenic activity of spironolactone is responsible for these effects, although this has not been established and spironolactone has been shown to possess insignificant progestogenic and antiprogestogenic activity even at high dosages in women. An alternative proposed cause is inhibition of 17?-hydroxylase and hence sex steroid metabolism by spironolactone and consequent changes in sex hormone levels. In any case, regardless of their mechanism, the menstrual disturbances associated with spironolactone can usually be controlled well by concomitant treatment with a birth control pill, due to the progestin component.
Rare reactions
Aside from hyperkalemia, spironolactone may rarely cause severe side effects such as anaphylaxis, kidney failure, hepatitis (two reported cases, neither serious), agranulocytosis, DRESS syndrome, Stevens-Johnson syndrome or toxic epidermal necrolysis. Five cases of breast cancer in patients who took spironolactone for prolonged periods of time have been reported. It should also be used with caution in people with some neurological disorders, no urine production, acute kidney injury, or significant impairment of kidney excretory function with risk of hyperkalemia.
Spironolactone bodies
Long-term administration of spironolactone gives the histologic characteristic of "spironolactone bodies" in the adrenal cortex. Spironolactone bodies are eosinophilic, round, concentrically laminated cytoplasmic inclusions surrounded by clear halos in preparations stained with hematoxylin and eosin.
Pregnancy and breastfeeding
Spironolactone is considered Pregnancy Category C meaning that it is unclear if it is safe for use during pregnancy. It is able to cross the placenta. Likewise, it has been found to be present in the breast milk of lactating mothers and, while the effects of spironolactone or its metabolites have not been extensively studied in breastfeeding infants, it is generally recommended that women also not take the medication while nursing. However, only very small amounts of spironolactone and its metabolite canrenone enter breast milk, and the amount received by an infant during breastfeeding (<0.5% of the mother's dose) is considered to be insignificant.
A study found that spironolactone was not associated with teratogenicity in the offspring of rats. Because it is an antiandrogen, however, spironolactone could theoretically have the potential to cause feminization of male fetuses at sufficient doses. In accordance, a subsequent study found that partial feminization of the genitalia occurred in the male offspring of rats that received doses of spironolactone that were five times higher than those normally used in humans (200 mg/kg per day). Another study found permanent, dose-related reproductive tract abnormalities rat offspring of both sexes at lower doses (50 to 100 mg/kg per day).
In practice however, although experience is limited, spironolactone has never been reported to cause observable feminization or any other congenital defects in humans. Among 31 human newborns exposed to spironolactone in the first trimester, there were no signs of any specific birth defects. A case report described a woman who was prescribed spironolactone during pregnancy with triplets and delivered all three (one boy and two girls) healthy; there was no feminization in the boy. In addition, spironolactone has been used at high doses to treat pregnant women with Bartter's syndrome, and none of the infants (three boys, two girls) showed toxicity, including feminization in the male infants. There are similar findings, albeit also limited, for another antiandrogen, cyproterone acetate (prominent genital defects in male rats, but no human abnormalities (including feminization of male fetuses) at both a low dose of 2 mg/day or high doses of 50 to 100 mg/day). In any case, spironolactone is nonetheless not recommended during pregnancy due to theoretical concerns relating to feminization of males and also to potential alteration of fetal potassium levels.
Overdose
Spironolactone is relatively safe in acute overdose. Symptoms following an acute overdose of spironolactone may include drowsiness, confusion, maculopapular or erythematous rash, nausea, vomiting, dizziness, and diarrhea. In rare cases, hyponatremia, hyperkalemia, or hepatic coma may occur in individuals with severe liver disease. However, these adverse reactions are unlikely in the event of an acute overdose. Hyperkalemia can occur following an overdose of spironolactone, and this is especially so in people with decreased kidney function. Spironolactone has been studied at extremely high oral doses of up to 2,400 mg per day in clinical trials. Its oral median lethal dose (LD50) is more than 1,000 mg/kg in mice, rats, and rabbits.
There is no specific antidote for overdose of spironolactone. Treatment may consist of induction of vomiting or stomach evacuation by gastric lavage. The treatment of spironolactone overdose is supportive, with the purpose of maintaining hydration, electrolyte balance, and vital functions. Spironolactone should be discontinued in people with impaired kidney function or hyperkalemia.
Interactions
Spironolactone often increases serum potassium levels and can cause hyperkalemia, a very serious condition. Therefore, it is recommended that people using this medication avoid potassium supplements and salt substitutes containing potassium. Physicians must be careful to monitor potassium levels in both males and females who are taking spironolactone as a diuretic, especially during the first twelve months of use and whenever the dosage is increased. Doctors may also recommend that some patients may be advised to limit dietary consumption of potassium-rich foods. However, recent data suggests that both potassium monitoring and dietary restriction of potassium intake is unnecessary in healthy young women taking spironolactone for acne. Spironolactone together with trimethoprim/sulfamethoxazole increases the likelihood of hyperkalemia, especially in the elderly. The trimethoprim portion acts to prevent potassium excretion in the distal tubule of the nephron.
Spironolactone has been reported to induce the enzymes CYP3A4 and certain UDP-glucuronosyltransferases (UGTs), which can result in interactions with various medications. However, it has also been reported that metabolites of spironolactone irreversibly inhibit CYP3A4. In any case, spironolactone has been found to reduce the bioavailability of oral estradiol, which could be due to induction of estradiol metabolism via CYP3A4. Spironolactone has also been found to inhibit UGT2B7. Spironolactone can also have numerous other interactions, most commonly with other cardiac and blood pressure medications, for instance digoxin.
Licorice, which has indirect mineralocorticoid activity by inhibiting mineralocorticoid metabolism, has been found to inhibit the antimineralocorticoid effects of spironolactone. Moreover, the addition of licorice to spironolactone has been found to reduce the antimineralocorticoid side effects of spironolactone in women treated with it for hyperandrogenism, and licorice hence may be used to reduce these side effects in women treated with spironolactone as an antiandrogen who are bothered by them. On the opposite end of the spectrum, spironolactone is useful in reversing licorice-induced hypokalemia. Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) have been found to attenuate the diuresis and natriuresis induced by spironolactone but not to affect its antihypertensive effect.
Some research has suggested that spironolactone might be able to interfere with the effectiveness of antidepressant treatment. As the medication acts as an antimineralocorticoid, it is thought that it might be able to reduce the effectiveness of certain antidepressants by interfering with normalization of the hypothalamic-pituitary-adrenal axis and by increasing levels of glucocorticoids such as cortisol. However, other research contradicts this hypothesis and has suggested that spironolactone might actually produce antidepressant effects, for instance studies showing antidepressant-like effects of spironolactone in animals.
Pharmacology
Pharmacodynamics
The pharmacodynamics of spironolactone are characterized by high antimineralocorticoid activity, moderate antiandrogenic activity, and weak steroidogenesis inhibition, among other more minor activities. Spironolactone is a prodrug, so most of its actions are actually mediated by its various active metabolites. The major active forms of spironolactone are 7?-thiomethylspironolactone (7?-TMS) and canrenone (7?-desthioacetyl-?6-spironolactone).
Spironolactone is a potent antimineralocorticoid. That is, it is an antagonist of the mineralocorticoid receptor (MR), the biological target of mineralocorticoids like aldosterone and 11-deoxycorticosterone. By blocking the MR, spironolactone inhibits the effects of mineralocorticoids in the body. The antimineralocorticoid activity of spironolactone is responsible for its therapeutic efficacy in the treatment of edema, high blood pressure, heart failure, hyperaldosteronism, and ascites due to cirrhosis. It is also responsible for many of the side effects of spironolactone, such as urinary frequency, dehydration, hyponatremia, low blood pressure, fatigue, dizziness, metabolic acidosis, decreased kidney function, and its risk of hyperkalemia.
Spironolactone is a moderate antiandrogen. That is, it is an antagonist of the androgen receptor (AR), the biological target of androgens like testosterone and dihydrotestosterone (DHT). By blocking the AR, spironolactone inhibits the effects of androgens in the body. The antiandrogenic activity of spironolactone is mainly responsible for its therapeutic efficacy in the treatment of androgen-dependent skin and hair conditions like acne, seborrhea, hirsutism, and pattern hair loss and hyperandrogenism in women, precocious puberty in boys with testotoxicosis, and as a component of feminizing hormone therapy for transgender women. It is also primarily responsible for some of its side effects, like breast tenderness, gynecomastia, feminization, and demasculinization in men. Blockade of androgen signaling in the breast disinhibits the actions of estrogens in this tissue. Although useful as an antiandrogen in women, who have low testosterone levels compared to men, spironolactone is described as having relatively weak antiandrogenic activity.
Spironolactone is a weak steroidogenesis inhibitor. That is, it inhibits steroidogenic enzymes, or enzymes involved in the production of steroid hormones. Spironolactone and/or its metabolites have been found in vitro to weakly inhibit a broad array of steroidogenic enzymes including cholesterol side-chain cleavage enzyme, 17?-hydroxylase, 17,20-lyase, 5?-reductase, 3?-hydroxysteroid dehydrogenase, 11?-hydroxylase, 21-hydroxylase, and aldosterone synthase (18-hydroxylase). However, although very high doses of spironolactone can considerably decrease steroid hormone levels in animals, spironolactone has shown mixed and inconsistent effects on steroid hormone levels in clinical studies, even at high clinical doses. In any case, the levels of most steroid hormones, including testosterone and cortisol, are usually unchanged by spironolactone in humans, which may in part be related to compensatory upregulation of their synthesis. The weak steroidogenesis inhibition of spironolactone might contribute to its antiandrogenic efficacy to some degree and may explain its side effect of menstrual irregularities in women.
Spironolactone has been found in some studies to increase levels of estradiol, an estrogen, although many other studies have found no changes in estradiol levels. The mechanism of how spironolactone increases estradiol levels is unclear, but it may involve inhibition of the inactivation of estradiol into estrone and enhancement of the peripheral conversion of testosterone into estradiol. It is notable that spironolactone has been found in vitro to act as a weak inhibitor of 17?-hydroxysteroid dehydrogenase 2, an enzyme that is involved in the conversion of estradiol into estrone. Increased levels of estradiol with spironolactone may be involved in its preservation of bone density and in its side effects such as breast tenderness, breast enlargement, and gynecomastia in women and men.
In response to the antimineralocorticoid activity spironolactone, and in an attempt to maintain homeostasis, the body increases aldosterone production in the adrenal cortex. Some studies have found that levels of cortisol, a glucocorticoid hormone that is also produced in the adrenal cortex, are increased as well. However, other clinical studies have found no change in cortisol levels with spironolactone, and those that have found increases often have observed only small changes. In accordance, spironolactone has not been associated with conventional glucocorticoid medication effects or side effects.
Other activities of spironolactone may include very weak interactions with the estrogen and progesterone receptors and agonism of the pregnane X receptor. These activities could contribute to the menstrual irregularities and breast side effects of spironolactone and to its drug interactions, respectively.
Pharmacokinetics
The pharmacokinetics of spironolactone have not been studied well, which is in part because it is an old medication that was developed in the 1950s. Nonetheless, much has been elucidated about the pharmacokinetics of spironolactone over the decades.
Absorption
The bioavailability of spironolactone when taken by mouth is 60 to 90%. The bioavailability of the medication improves significantly when it is taken with food. The relationship between a single dose of spironolactone and plasma levels of canrenone, a major active metabolite of spironolactone, has been found to be linear across a dose range of 25 to 200 mg spironolactone. Steady-state concentrations of spironolactone are achieved within 8 days of treatment initiation.
Little or no systemic absorption has been observed with topical spironolactone.
Distribution
Spironolactone and its metabolite canrenone are highly plasma protein bound, with percentages of 88.0% and 99.2%, respectively. Spironolactone is bound equivalently to albumin and ?1-acid glycoprotein, while canrenone is bound only to albumin. Spironolactone and its metabolite 7?-thiospironolactone show very low or negligible affinity for sex hormone-binding globulin (SHBG). In accordance, a study of high-dosage spironolactone treatment found no change in steroid binding capacity related to SHBG or to corticosteroid-binding globulin (CBG), suggesting that spironolactone does not displace steroid hormones from their carrier proteins. This is in contradiction with widespread statements that spironolactone increases free estradiol levels by displacing estradiol from SHBG.
Metabolism
Spironolactone is rapidly and extensively metabolized in the liver upon oral administration and has a very short terminal half-life of 1.4 hours. The major metabolites of spironolactone are 7?-thiomethylspironolactone (7?-TMS), 6?-hydroxy-7?-thiomethylspironolactone (6?-OH-7?-TMS), and canrenone (7?-desthioacetyl-?6-spironolactone). These metabolites have much longer elimination half-lives than spironolactone of 13.8 hours, 15.0 hours, and 16.5 hours, respectively, and are responsible for the therapeutic effects of the medication. As such, spironolactone is a prodrug. The 7?-thiomethylated metabolites of spironolactone were not known for many years and it was originally thought that canrenone was the major active metabolite of the medication, but subsequent research identified 7?-TMS as the major metabolite. Other known but more minor metabolites of spironolactone include 7?-thiospironolactone (7?-TS), which is an important intermediate to the major metabolites of spironolactone, as well as the 7?-methyl ethyl ester of spironolactone and the 6?-hydroxy-7?-methyl ethyl ester of spironolactone.
Spironolactone is hydrolyzed or deacetylated at the thioester of the C7? position into 7?-TS by carboxylesterases. Following formation of 7?-TS, it is S-oxygenated by flavin-containing monooxygenases to form an electrophilic sulfenic acid metabolite. This metabolite is involved in the CYP450 inhibition of spironolactone, and also binds covalently to other proteins. 7?-TS is also S-methylated into 7?-TMS, a transformation catalyzed by thiol S-methyltransferase. Unlike the related medication eplerenone, spironolactone is said to not be metabolized by CYP3A4. However, hepatic CYP3A4 is likely responsible for the 6?-hydroxylation of 7?-TMS into 6?-OH-7?-TMS. 7?-TMS may also be hydroxylated at the C3? and C3? positions. Spironolactone is dethioacetylated into canrenone. Finally, the C17 ?-lactone ring of spironolactone is hydrolyzed by the paraoxonase PON3. It was originally thought to be hydrolyzed by PON1, but this was due to contamination with PON3.
Elimination
The majority of spironolactone is eliminated by the kidneys, while minimal amounts are handled by biliary excretion.
Chemistry
Spironolactone, also known as 7?-acetylthiospirolactone, is a steroidal 17?-spirolactone, or more simply a spirolactone. It can most appropriately be conceptualized as a derivative of progesterone, itself also a potent antimineralocorticoid, in which a hydroxyl group has been substituted at the C17? position (as in 17?-hydroxyprogesterone), the acetyl group at the C17? position has been cyclized with the C17? hydroxyl group to form a spiro 21-carboxylic acid ?-lactone ring, and an acetylthio group has been substituted in at the C7? position. These structural modifications of progesterone confer increased oral bioavailability and potency, potent antiandrogenic activity, and strongly reduced progestogenic activity. The C7? substitution is likely responsible for or involved in the antiandrogenic activity of spironolactone, as 7?-thioprogesterone (SC-8365), unlike progesterone, is an antiandrogen with similar affinity to the AR as that of spironolactone. In addition, the C7? substitution appears to be responsible for the loss of progestogenic activity and good oral bioavailability of spironolactone, as SC-5233, the analogue of spironolactone without a C7? substitution, has potent progestogenic activity but very poor oral bioavailability similarly to progesterone.
Names
Spironolactone is also known by the following equivalent chemical names:
- 7?-Acetylthio-17?-hydroxy-3-oxopregn-4-ene-21-carboxylic acid ?-lactone
- 7?-Acetylthio-3-oxo-17?-pregn-4-ene-21,17?-carbolactone
- 3-(3-Oxo-7?-acetylthio-17?-hydroxyandrost-4-en-17?-yl)propionic acid lactone
- 7?-Acetylthio-17?-(2-carboxyethyl)androst-4-en-17?-ol-3-one ?-lactone
- 7?-Acetylthio-17?-(2-carboxyethyl)testosterone ?-lactone
Analogues
Spironolactone is closely related structurally to other clinically used spirolactones such as canrenone, potassium canrenoate, drospirenone, and eplerenone, as well as to the never-marketed spirolactones SC-5233 (6,7-dihydrocanrenone; 7?-desthioacetylspironolactone), SC-8109 (19-nor-6,7-dihydrocanrenone), spiroxasone, prorenone (SC-23133), mexrenone (SC-25152, ZK-32055), dicirenone (SC-26304), spirorenone (ZK-35973), and mespirenone (ZK-94679).
Synthesis
Chemical syntheses of spironolactone and its analogues and derivatives have been described and reviewed.
History
The natriuretic effects of progesterone were demonstrated in 1955, and the development of spironolactone as a synthetic antimineralocorticoid analogue of progesterone shortly followed this. Spironolactone was first synthesized in 1957, was patented between 1958 and 1961, and was first marketed, as an antimineralocorticoid, in 1959. The antiandrogenic activity of spironolactone was first discovered and reported in 1969, which shortly followed the discovery in 1968 that gynecomastia, a frequent and by that time well-established side effect of spironolactone, is an important and major side effect of AR antagonists. The medication started to be used as an antiandrogen, for instance in the treatment of hirsutism in women, by the late 1970s and early 1980s, and has since become the most widely used antiandrogen for dermatological indications in the United States.
Society and culture
Generic names
The English, French, and generic name of the medication is spironolactone and this is its INN, USAN, USP, BAN, DCF, and JAN. Its name is spironolactonum in Latin, spironolacton in German, espironolactona in Spanish and Portuguese, and spironolattone in Italian (which is also its DCIT).
Spironolactone is also known by its developmental code names SC-9420 and NSC-150339.
Brand names
Spironolactone is marketed under a large number of brand names throughout the world. The major brand name of spironolactone is Aldactone. Other important brand names include Aldactone-A, Berlactone, CaroSpir, Espironolactona, Espironolactona Genfar, Novo-Spiroton, Prilactone (veterinary), Spiractin, Spiridon, Spirix, Spiroctan, Spiroderm (discontinued), Spirogamma, Spirohexal, Spirolon, Spirolone, Spiron, Spironolactone Actavis, Spironolactone Orion, Spironolactone Teva, Spirotone, Tempora (veterinary), Uractone, Uractonum, Verospiron, and Vivitar.
Spironolactone is also formulated in combination with a variety of other medications, including with hydrochlorothiazide as Aldactazide, with hydroflumethiazide as Aldactide, Lasilacton, Lasilactone, and Spiromide, with altizide as Aldactacine and Aldactazine, with furosemide as Fruselac, with benazepril as Cardalis (veterinary), with metolazone as Metolactone, with bendroflumethiazide as Sali-Aldopur, and with torasemide as Dytor Plus, Torlactone, and Zator Plus.
Availability
Spironolactone is marketed widely throughout the world and is available in almost every country, including in the United States, Canada, the United Kingdom, other European countries, Australia, New Zealand, South Africa, Central and South America, and East and Southeast Asia.
Research
Enlarged prostate
Spironolactone has been studied at a high dosage in the treatment of benign prostatic hyperplasia (BPH; enlarged prostate). It was found to be better than placebo in terms of symptom relief following three months of treatment. However, this was not maintained after six months of treatment, by which point the improvements had largely disappeared. Moreover, no difference was observed between spironolactone and placebo with regard to volume of residual urine or prostate size. Gynecomastia was observed in about 5% of people. On the basis of these results, it has been said that spironolactone has no place in the treatment of BPH.
Epstein-Barr virus
Spironolactone has been found to block Epstein-Barr virus (EBV) production and that of other human herpesviruses by inhibiting the function of an EBV protein SM, which is essential for infectious virus production. This effect of spironolactone was determined to be independent of its antimineralocorticoid actions. Thus, spironolactone or compounds based on it have the potential to yield novel antiviral medications with a distinct mechanism of action and limited toxicity.
Other conditions
Spironolactone has been studied in fibromyalgia in women. It has also been studied in bulimia nervosa in women, but was not found to be effective.
References
External links
- Spironolactone - MedlinePlus - U.S. National Library of Medicine
- Aldactone (spironolactone) patient information leaflet - PDR+
Source of article : Wikipedia
0 Comments