Spironolactone (pronounced /spɪˌrɒnɵˈlæktoʊn/,[2] and commonly shortened simply to "spiro") (INN, BAN, USAN),[3] marketed mainly under the brand name Aldactone in most countries, is a synthetic, steroidal antimineralocorticoid, antiandrogen, and, to a lesser extent, progestin. It belongs to a class of pharmaceutical drugs known as potassium-sparing diuretics, and is used primarily as a diuretic and antihypertensive in the treatment of heart failure and hypertension. As a secondary use, spironolactone is also frequently employed off-label for the purpose of reducing elevated or unwanted androgen levels and activity in the body, such as in the treatment of hyperandrogenism in women and, especially, as a component of hormone replacement therapy for trans women.[4]
Spironolactone is a relatively old drug, having been introduced clinically in 1959.[5][6] Futterman and Lemberg predicted that spironolactone will be less commonly used in cardiovascular conditions as newer agents such as eplerenone are more selective and produce fewer side effects – namely, antiandrogenic side effects.[7] However, spironolactone remains widely used for indications in which its antiandrogen effects are the intention of treatment.
Spironolactone is on the World Health Organization's List of Essential Medicines, a list of the most important medication needed in a basic health system.[8]
Contents [hide]
1 Medical uses
1.1 Diuretic/antihypertensive
1.2 Antiandrogen
2 Adverse reactions
2.1 Side effects
2.2 Interactions
2.3 Contraindications
3 Pharmacology
3.1 Activity profile
3.2 Antimineralocorticoidic
3.3 Antiglucocorticoidic
3.4 Antiandrogenic
3.5 Progestogenic
3.6 Estrogenic
4 Pharmacokinetics
5 Spironolactone bodies
6 Synthesis 1
7 Synthesis 2
8 See also
9 References
10 External links
Medical uses[edit]
Diuretic/antihypertensive[edit]
Spironolactone is used primarily to treat heart failure, edematous conditions such as nephrotic syndrome or ascites in patients with liver disease, essential hypertension, hypokalemia, secondary hyperaldosteronism (such as occurs with hepatic cirrhosis), and Conn's syndrome (primary hyperaldosteronism). 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. About one person in one hundred with hypertension has elevated levels of aldosterone; in these persons, 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.
While loop diuretics remain first-line for most patients 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 <35%.[9]
In a randomized evaluation which studied people with severe congestive heart failure, patients 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 drug. Patients in the study's intervention arm also had fewer symptoms of heart failure and were hospitalized less frequently.[10] Likewise, it has shown benefit for and is recommended in patients who recently suffered a heart attack and have an ejection fraction <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.[11] 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.[12]
It is recommended that alternatives to spironolactone be considered if serum creatinine is >2.5 mg/dL (221µmol/L) in males or >2 mg/dL (176.8 µmol/L) in females, if glomerular filtration rate is below 30mL/min or with a serum potassium of >5.0 mEq/L given the potential for adverse events detailed elsewhere in this article. Doses should be adjusted according to the degree of renal function as well.[9]
Because spironolactone reduces the body's production of testosterone, it can be quite effective in clearing severe acne conditions, such as cystic acne, caused by slightly elevated or elevated levels of testosterone in women. In reducing the levels of testosterone, excess oil that is naturally produced in the skin is also reduced. Though not the primary intended purpose of the medication, its ability to be helpful with problematic skin and acne conditions was discovered to be one of the beneficial side effects and has been quite successful. Often times, for women treating acne, spironolactone is prescribed and paired with a birth control pill. A significant amount of patients have reported that they have seen positive results in the pairing of these two medications, although these results may not be seen for up to three months.
Because spironolactone reduces the body's production of testosterone and blocks the androgen receptors, it can cause effects associated with low testosterone 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. The newer drug, eplerenone has been approved by the U.S. Food and Drug Administration for treatment of heart failure, but lacks the rather potent antiandrogen effects and thus is far more suitable for men for whom long term medication is being chosen. 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 cardiac arrythmias. Physicians must be careful to monitor potassium levels in both males and females who are taking spironolactone, especially during the first twelve months of use and whenever the dosage is increased.
Antiandrogen[edit]
Spironolactone is a potent antagonist of the androgen receptor as well as an inhibitor of androgen production. Due to the antiandrogenic effects that result from these actions, it is frequently used off-label to treat a variety of dermatological conditions in which androgens, such as testosterone and dihydrotestosterone (DHT), play a role. Some of these uses include androgenic alopecia in men (either at low doses or as a topical formulation) and women, and hirsutism, acne, and seborrhea in women.[13] Higher doses are not recommended for males due to the high risk of feminization and other side effects. Similarly, it is also commonly used to treat symptoms of hyperandrogenism in polycystic ovary syndrome.[14]
Spironolactone is frequently used as a component of hormone replacement therapy in trans women, usually in addition to an estrogen. It is generally recommended to be prescribed at a dose of 100–200 mg per day for this purpose,[15][16] though it is frequently used at doses up to 300–400 mg in cases of treatment-resistant individuals, and doses as high as 600 mg have been used in some clinical studies with additional benefits seen.[17] Spironolactone significantly depresses plasma testosterone levels, reducing them to female/castrate levels at sufficient doses and in combination with estrogen. The clinical response consists of, among other effects, decreased male pattern body hair, the induction of breast development, feminization in general, and lack of spontaneous erections.[17]
There are very few available options for androgen receptor antagonist drug therapy. Spironolactone, cyproterone acetate, and flutamide are the most well-known and widely used agents.[18] Compared to cyproterone acetate, spironolactone is considerably less potent as an antiandrogen by weight and binding affinity to the androgen receptor.[19][20] However, despite this, at the doses in which they are typically used, spironolactone and cyproterone acetate have been found to be generally equivalent in terms of effectiveness for a variety of androgen-related conditions;[21] though, cyproterone acetate has shown a slight though non-statistically significant advantage in some studies.[22][23] Also, it has been suggested that cyproterone acetate could be more effective in cases where androgen levels are more pronounced, though this has not been proven.[21] Flutamide, another frequently employed antiandrogen which is a pure, selective androgen receptor antagonist, though much less potent by weight and binding affinity than either spironolactone or cyproterone acetate,[24][25] has been found to be more effective than either of them as an antiandrogen when it is used at the typical treatment doses.[19][26][27] Unfortunately, the uses of both cyproterone acetate and flutamide have been associated with hepatotoxicity, which can be severe with flutamide and has resulted in the withdrawal of cyproterone acetate from the US drug market for this indication. 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.[16] Thus, spironolactone may be the only practical, safe, and available option in many cases.
Adverse reactions[edit]
Side effects[edit]
The most common side effect of spironolactone is urinary frequency. Other general side effects include ataxia, drowsiness, dry skin, and rashes. Because it reduces androgen levels and blocks androgen receptors, spironolactone can, in males, cause breast tenderness, gynecomastia, and physical feminization in general, as well as testicular atrophy, reversible infertility, and sexual dysfunction, including loss of libido and erectile dysfunction.[28] In females, spironolactone can cause menstrual irregularities and breast tenderness and enlargement, likely due to a combination of its progestogenic and indirect estrogenic actions.[13]
The most important potential side effect of spironolactone is hyperkalemia, which can be life-threatening. Spironolactone may put patients 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 drug and bleeding from the stomach and duodenum, though a causal relationship between the two has not been established.[29] Also, it has been shown to be immunosuppressive in the treatment of sarcoidosis.[30]
Spironolactone may rarely cause more severe side effects such as anaphylaxis, renal failure, hepatotoxicity, agranulocytosis, DRESS syndrome, Stevens-Johnson Syndrome or toxic epidermal necrolysis.[31][32]
Interactions[edit]
Spironolactone often increases serum potassium levels and can cause hyperkalemia, a very serious condition. Therefore, it is recommended that people using this drug avoid potassium supplements and salt substitutes containing potassium.[33] Doctors usually recommend periodic screening of serum potassium levels and some patients may be advised to limit dietary consumption of potassium-rich foods.
Research has suggested that spironolactone may be able to interfere with the effectiveness of antidepressant treatment. As the drug acts as an antagonist of the mineralocorticoid receptor, it is thought that it may reduce the effectiveness of certain antidepressants by interfering with normalization of the hypothalamic-pituitary-adrenal axis and increasing glucocorticoid levels.[34][35] However, other research contradicts this hypothesis and has suggested that spironolactone may actually produce antidepressant-like effects.[36]
Spironolactone can also have numerous other interactions, most commonly with other cardiac and blood pressure medications.[37]
Contraindications[edit]
Spironolactone is considered Pregnancy Category C by the FDA and should not be taken by pregnant women due to the high risk of birth defects and feminization of male fetuses. 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 breast-feeding infants, it is generally recommended that women also not take the drug while nursing.[13][37]
It should also be used with caution in patients with some neurological disorders, anuria, acute kidney injury, or significant impairment of renal excretory function with risk of hyperkalemia.[37]
Pharmacology[edit]
Activity profile[edit]
Spironolactone is known to possess the following pharmacological activity:[38]
Mineralocorticoid receptor (MR) antagonist (IC50 = 24 nM)
Androgen receptor (AR) antagonist/very weak partial agonist (IC50 = 77 nM)
Progesterone receptor agonist (EC50 = 740 nM)
Glucocorticoid receptor antagonist (IC50 = 2,410 nM)
Steroid 11β-hydroxylase, aldosterone synthase (18-hydroxylase), 17α-hydroxylase, and 17,20-lyase inhibitor
Pregnane X receptor (PXR) agonist (and thus indirect CYP3A4 and P-glycoprotein inducer)[39][40][41]
There is also evidence that spironolactone may block voltage-dependent Ca2+ channels.[42][43]
Spironolactone does not have significant affinity for either of the estrogen receptors (ERα or ERβ), nor is its low affinity for the GR thought to be of significance at clinically-relevant concentrations.
Antimineralocorticoidic[edit]
Spironolactone inhibits the effects of mineralocorticoids, namely, aldosterone, by displacing them from mineralocorticoid receptors (MR) in the cortical collecting duct of renal nephrons. This decreases the reabsorption of sodium and water, while limiting the excretion of potassium (A K+ sparing diuretic). The drug has a slightly delayed onset of action, and so it takes several days for diuresis to occur. This is because the MR is a nuclear receptor which works through regulating gene transcription and gene expression, in this case to decrease the production and expression of ENaC and ROMK electrolyte channels in the distal nephrons. In addition to direct antagonism of the MRs, the antimineralocorticoid effects of spironolactone may also in part be mediated by direct inactivation of steroid 11β-hydroxylase and aldosterone synthase (18-hydroxylase), enzymes involved in the biosynthesis of mineralocorticoids. If levels of mineralocorticoids are decreased then there are lower circulating levels to compete with spironolactone to influence gene expression as mentioned above.[44]
Antiglucocorticoidic[edit]
Spironolactone has been shown to inhibit steroid 11β-hydroxylase, an enzyme that is essential for the production of the glucocorticoid hormone cortisol. Because of this, glucocorticoid levels would in theory be lowered alongside the lower levels of mineralocorticoids (i.e. spironolactone should also produce some degree of antiglucocorticoid effect). In clinical practice however, this has not been found to be the case, as spironolactone has actually been shown to increase cortisol levels, both with acute and chronic administration. Research has shown that this is due to antagonism of the MR, which suppresses negative feedback on the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis positively regulates the secretion of adrenocorticotropic hormone (ACTH), which in turn signals the adrenal glands – the major source of corticosteroid biosynthesis in the body – to increase production of glucocorticoids as well. Therefore, by disinhibiting the regulation on ACTH, its levels rise and spironolactone essentially causes an indirect rise in cortisol production.[45][46] Thus, any antiglucocorticoid activity of spironolactone via direct suppression of glucocorticoid synthesis (at the level of the adrenals) appears to be more than fully offset by its concurrent indirect stimulatory effects on glucocorticoid production secondary to ACTH.
Antiandrogenic[edit]
Spironolactone mediates its antiandrogenic effects via multiple actions, including the following:
Direct blockade of androgens from interacting with the androgen receptor.[47][48] It should be noted however that spironolactone, similarly to other steroidal antiandrogens such as cyproterone acetate, is not a pure, or silent, antagonist of the androgen receptor, but rather a weak partial agonist with the capacity for both agonist and antagonist effects.[49][50][51] However, in the presence of significant enough levels of potent full agonists like testosterone and DHT,[51] the cases in which it is usually used even with regards to the "lower" relative levels present in females, spironolactone will behave similar to a pure antagonist. Nonetheless, there may still be a potential for spironolactone to produce androgenic effects (i.e. act as a receptor agonist) in the body at sufficiently high doses and/or in those with low enough endogenous androgen concentrations. As an example, one condition in which spironolactone is contraindicated is prostate cancer,[52] as the drug has been shown in vitro to significantly accelerate carcinoma growth in the absence of any other androgens, and was found to do so at the relatively high rate of approximately 32%, which was about 35% that of DHT (thus also indicating that its potential intrinsic activity at the androgen receptor may be somewhere around one-third that of endogenous full agonists).[49]
Inhibition of 17α-hydroxylase and 17,20-desmolase, enzymes in the androgen biosynthesis pathway, which in turn results in decreased testosterone and dihydrotestosterone (DHT) levels.[48][53][54][55] Though, its inhibition of these enzymes is said to be relatively weak.[25]
Activation of the progesterone receptor, as, in sufficient amounts, this results in an antigonadotropic effect due to negative feedback on the hypothalamic-pituitary-gonadal axis, which in turn reduces sex steroid production and by extension androgen levels.
Inhibition of 5α-reductase, the enzyme responsible for converting testosterone into the 3- to 10-fold more potent androgen dihydrotestosterone (DHT). However, there is conflicting data on the ability of spironolactone to affect this enzyme. An in vitro study of the effect of spironolactone on prostate tissue 5α-reductase activity found no change even with very high concentrations of the drug.[47] In contrast, another study, after one month of treatment of spironolactone at a dose of 100 mg per day via the oral route, found a significant in vivo inhibitory effect of spironolactone on genital skin 5α-reductase activity in hirsute women as well as an inhibitory effect of the drug on 5α-reductase activity in normal genital skin in vitro, and concluded that spironolactone directly inhibits the 5α-reductase enzyme and that the property could play a role of the beneficial effects of the drug on hirsutism.[56] However, another study of spironolactone in hirsute women, after 6 months of treatment at the same dose (100 mg/d orally), found no significant effects of the drug on the serum ratios of testosterone to DHT and its metabolites—a reliable marker of 5α-reductase activity—whereas significant changes were found with 5 mg per day oral finasteride, a well-established 5α-reductase inhibitor.[57] Finally, yet another study of spironolactone in hirsute women, after 3 months of treatment at a higher dose of 200 mg per day orally, did report significant changes, in the same metabolic markers of 5α-reductase activity.[58] In summation then, whether spironolactone actually inhibits 5α-reductase to some clinical end-point or not and how it may do so remain unclear. It can be deduced from comparison studies, however, that if it does have an effect at reducing hirsutism, it is not as effective as more potent and selective 5α-reductase inhibitors like finasteride. Supporting this conclusion is another trial in which the combination of 100 mg/d spironolactone and 5 mg/d finasteride was found to be significantly more effective than spironolactone alone in the treatment of hirsutism in women.[59]
Acceleration of the rate of metabolism/clearance of testosterone by enhancing the rate of peripheral conversion of testosterone to estradiol.[54]
Progestogenic[edit]
Spironolactone has weak progestogenic properties.[25][60] Its actions in this regard are a result of direct agonist activity at the progesterone receptor, but with a half-maximal potency approximately one tenth that of its activity at the androgen receptor.[38] Spironolactone's progestogenic actions are thought to be responsible for some of its side effects,[61] including the menstrual irregularities seen in women and the undesirable serum lipid profile changes that are seen at higher doses.[24][62][63] They may also serve to augment the gynecomastia caused by the estrogenic effects of spironolactone,[64] as progesterone is known to play a role in breast development.[65]
Estrogenic[edit]
Spironolactone has some indirect estrogenic effects which it mediates via several actions, including the following:
By acting as an antiandrogen, as androgens suppress both estrogen production and action.[48][66]
Displacement of estrogens from sex hormone-binding globulin (SHBG).[53] This occurs because spironolactone binds to SHBG at a relatively high rate, as do endogenous estrogens and androgens, but estrogens like estradiol and estrone are more easily displaced than are androgens like testosterone. As a result, spironolactone blocks relatively more estrogens from interacting with SHBG than androgens, resulting in a higher ratio of free estrogens to free androgens.[67]
Inhibition of the conversion of estradiol to estrone, resulting in an increase in the ratio of estradiol to estrone.[68] This is important because estradiol is approximately 10 times as potent as estrone as an estrogen.[69]
Enhancement of the rate of peripheral conversion of testosterone to estradiol, thus further lowering testosterone levels and increasing estradiol levels.[54]
Pharmacokinetics[edit]
Spironolactone has an onset of action of about 2–3 hours after taking the first dose, with a half-life of about 1–2 hours. Due to its relatively short half-life, it is thought that spironolactone may behave mainly as a prodrug to an array of active metabolites with much longer half-lives (e.g., 12–20 hours in the case of canrenone). Some of its metabolites include canrenone, canrenoic acid, 7α-methylthiospironolactone, and 6β-hydroxy-7α-methylthiospironolactone, among many others. The drug is highly plasma protein bound. It is metabolized by the liver, from which it is partially eliminated with the majority being handled by the kidneys. Minimal amounts are handled by biliary excretion.[1]
Of note, the clinical benefits of the drug when used a diuretic are typically not seen until 2–3 days after dosing begins, perhaps accounted for by the need for 4-5 doses before reaching a steady state concentration. Likewise, the maximal antihypertensive effective may not be seen for 2–3 weeks.
The bioavailability of spironolactone improves significantly when it is taken with food.[70][71]
Spironolactone bodies[edit]
Micrograph of an adrenal gland spironolactone bodies. H&E stain.
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.[72]
Spironolactone is a relatively old drug, having been introduced clinically in 1959.[5][6] Futterman and Lemberg predicted that spironolactone will be less commonly used in cardiovascular conditions as newer agents such as eplerenone are more selective and produce fewer side effects – namely, antiandrogenic side effects.[7] However, spironolactone remains widely used for indications in which its antiandrogen effects are the intention of treatment.
Spironolactone is on the World Health Organization's List of Essential Medicines, a list of the most important medication needed in a basic health system.[8]
Contents [hide]
1 Medical uses
1.1 Diuretic/antihypertensive
1.2 Antiandrogen
2 Adverse reactions
2.1 Side effects
2.2 Interactions
2.3 Contraindications
3 Pharmacology
3.1 Activity profile
3.2 Antimineralocorticoidic
3.3 Antiglucocorticoidic
3.4 Antiandrogenic
3.5 Progestogenic
3.6 Estrogenic
4 Pharmacokinetics
5 Spironolactone bodies
6 Synthesis 1
7 Synthesis 2
8 See also
9 References
10 External links
Medical uses[edit]
Diuretic/antihypertensive[edit]
Spironolactone is used primarily to treat heart failure, edematous conditions such as nephrotic syndrome or ascites in patients with liver disease, essential hypertension, hypokalemia, secondary hyperaldosteronism (such as occurs with hepatic cirrhosis), and Conn's syndrome (primary hyperaldosteronism). 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. About one person in one hundred with hypertension has elevated levels of aldosterone; in these persons, 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.
While loop diuretics remain first-line for most patients 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 <35%.[9]
In a randomized evaluation which studied people with severe congestive heart failure, patients 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 drug. Patients in the study's intervention arm also had fewer symptoms of heart failure and were hospitalized less frequently.[10] Likewise, it has shown benefit for and is recommended in patients who recently suffered a heart attack and have an ejection fraction <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.[11] 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.[12]
It is recommended that alternatives to spironolactone be considered if serum creatinine is >2.5 mg/dL (221µmol/L) in males or >2 mg/dL (176.8 µmol/L) in females, if glomerular filtration rate is below 30mL/min or with a serum potassium of >5.0 mEq/L given the potential for adverse events detailed elsewhere in this article. Doses should be adjusted according to the degree of renal function as well.[9]
Because spironolactone reduces the body's production of testosterone, it can be quite effective in clearing severe acne conditions, such as cystic acne, caused by slightly elevated or elevated levels of testosterone in women. In reducing the levels of testosterone, excess oil that is naturally produced in the skin is also reduced. Though not the primary intended purpose of the medication, its ability to be helpful with problematic skin and acne conditions was discovered to be one of the beneficial side effects and has been quite successful. Often times, for women treating acne, spironolactone is prescribed and paired with a birth control pill. A significant amount of patients have reported that they have seen positive results in the pairing of these two medications, although these results may not be seen for up to three months.
Because spironolactone reduces the body's production of testosterone and blocks the androgen receptors, it can cause effects associated with low testosterone 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. The newer drug, eplerenone has been approved by the U.S. Food and Drug Administration for treatment of heart failure, but lacks the rather potent antiandrogen effects and thus is far more suitable for men for whom long term medication is being chosen. 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 cardiac arrythmias. Physicians must be careful to monitor potassium levels in both males and females who are taking spironolactone, especially during the first twelve months of use and whenever the dosage is increased.
Antiandrogen[edit]
Spironolactone is a potent antagonist of the androgen receptor as well as an inhibitor of androgen production. Due to the antiandrogenic effects that result from these actions, it is frequently used off-label to treat a variety of dermatological conditions in which androgens, such as testosterone and dihydrotestosterone (DHT), play a role. Some of these uses include androgenic alopecia in men (either at low doses or as a topical formulation) and women, and hirsutism, acne, and seborrhea in women.[13] Higher doses are not recommended for males due to the high risk of feminization and other side effects. Similarly, it is also commonly used to treat symptoms of hyperandrogenism in polycystic ovary syndrome.[14]
Spironolactone is frequently used as a component of hormone replacement therapy in trans women, usually in addition to an estrogen. It is generally recommended to be prescribed at a dose of 100–200 mg per day for this purpose,[15][16] though it is frequently used at doses up to 300–400 mg in cases of treatment-resistant individuals, and doses as high as 600 mg have been used in some clinical studies with additional benefits seen.[17] Spironolactone significantly depresses plasma testosterone levels, reducing them to female/castrate levels at sufficient doses and in combination with estrogen. The clinical response consists of, among other effects, decreased male pattern body hair, the induction of breast development, feminization in general, and lack of spontaneous erections.[17]
There are very few available options for androgen receptor antagonist drug therapy. Spironolactone, cyproterone acetate, and flutamide are the most well-known and widely used agents.[18] Compared to cyproterone acetate, spironolactone is considerably less potent as an antiandrogen by weight and binding affinity to the androgen receptor.[19][20] However, despite this, at the doses in which they are typically used, spironolactone and cyproterone acetate have been found to be generally equivalent in terms of effectiveness for a variety of androgen-related conditions;[21] though, cyproterone acetate has shown a slight though non-statistically significant advantage in some studies.[22][23] Also, it has been suggested that cyproterone acetate could be more effective in cases where androgen levels are more pronounced, though this has not been proven.[21] Flutamide, another frequently employed antiandrogen which is a pure, selective androgen receptor antagonist, though much less potent by weight and binding affinity than either spironolactone or cyproterone acetate,[24][25] has been found to be more effective than either of them as an antiandrogen when it is used at the typical treatment doses.[19][26][27] Unfortunately, the uses of both cyproterone acetate and flutamide have been associated with hepatotoxicity, which can be severe with flutamide and has resulted in the withdrawal of cyproterone acetate from the US drug market for this indication. 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.[16] Thus, spironolactone may be the only practical, safe, and available option in many cases.
Adverse reactions[edit]
Side effects[edit]
The most common side effect of spironolactone is urinary frequency. Other general side effects include ataxia, drowsiness, dry skin, and rashes. Because it reduces androgen levels and blocks androgen receptors, spironolactone can, in males, cause breast tenderness, gynecomastia, and physical feminization in general, as well as testicular atrophy, reversible infertility, and sexual dysfunction, including loss of libido and erectile dysfunction.[28] In females, spironolactone can cause menstrual irregularities and breast tenderness and enlargement, likely due to a combination of its progestogenic and indirect estrogenic actions.[13]
The most important potential side effect of spironolactone is hyperkalemia, which can be life-threatening. Spironolactone may put patients 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 drug and bleeding from the stomach and duodenum, though a causal relationship between the two has not been established.[29] Also, it has been shown to be immunosuppressive in the treatment of sarcoidosis.[30]
Spironolactone may rarely cause more severe side effects such as anaphylaxis, renal failure, hepatotoxicity, agranulocytosis, DRESS syndrome, Stevens-Johnson Syndrome or toxic epidermal necrolysis.[31][32]
Interactions[edit]
Spironolactone often increases serum potassium levels and can cause hyperkalemia, a very serious condition. Therefore, it is recommended that people using this drug avoid potassium supplements and salt substitutes containing potassium.[33] Doctors usually recommend periodic screening of serum potassium levels and some patients may be advised to limit dietary consumption of potassium-rich foods.
Research has suggested that spironolactone may be able to interfere with the effectiveness of antidepressant treatment. As the drug acts as an antagonist of the mineralocorticoid receptor, it is thought that it may reduce the effectiveness of certain antidepressants by interfering with normalization of the hypothalamic-pituitary-adrenal axis and increasing glucocorticoid levels.[34][35] However, other research contradicts this hypothesis and has suggested that spironolactone may actually produce antidepressant-like effects.[36]
Spironolactone can also have numerous other interactions, most commonly with other cardiac and blood pressure medications.[37]
Contraindications[edit]
Spironolactone is considered Pregnancy Category C by the FDA and should not be taken by pregnant women due to the high risk of birth defects and feminization of male fetuses. 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 breast-feeding infants, it is generally recommended that women also not take the drug while nursing.[13][37]
It should also be used with caution in patients with some neurological disorders, anuria, acute kidney injury, or significant impairment of renal excretory function with risk of hyperkalemia.[37]
Pharmacology[edit]
Activity profile[edit]
Spironolactone is known to possess the following pharmacological activity:[38]
Mineralocorticoid receptor (MR) antagonist (IC50 = 24 nM)
Androgen receptor (AR) antagonist/very weak partial agonist (IC50 = 77 nM)
Progesterone receptor agonist (EC50 = 740 nM)
Glucocorticoid receptor antagonist (IC50 = 2,410 nM)
Steroid 11β-hydroxylase, aldosterone synthase (18-hydroxylase), 17α-hydroxylase, and 17,20-lyase inhibitor
Pregnane X receptor (PXR) agonist (and thus indirect CYP3A4 and P-glycoprotein inducer)[39][40][41]
There is also evidence that spironolactone may block voltage-dependent Ca2+ channels.[42][43]
Spironolactone does not have significant affinity for either of the estrogen receptors (ERα or ERβ), nor is its low affinity for the GR thought to be of significance at clinically-relevant concentrations.
Antimineralocorticoidic[edit]
Spironolactone inhibits the effects of mineralocorticoids, namely, aldosterone, by displacing them from mineralocorticoid receptors (MR) in the cortical collecting duct of renal nephrons. This decreases the reabsorption of sodium and water, while limiting the excretion of potassium (A K+ sparing diuretic). The drug has a slightly delayed onset of action, and so it takes several days for diuresis to occur. This is because the MR is a nuclear receptor which works through regulating gene transcription and gene expression, in this case to decrease the production and expression of ENaC and ROMK electrolyte channels in the distal nephrons. In addition to direct antagonism of the MRs, the antimineralocorticoid effects of spironolactone may also in part be mediated by direct inactivation of steroid 11β-hydroxylase and aldosterone synthase (18-hydroxylase), enzymes involved in the biosynthesis of mineralocorticoids. If levels of mineralocorticoids are decreased then there are lower circulating levels to compete with spironolactone to influence gene expression as mentioned above.[44]
Antiglucocorticoidic[edit]
Spironolactone has been shown to inhibit steroid 11β-hydroxylase, an enzyme that is essential for the production of the glucocorticoid hormone cortisol. Because of this, glucocorticoid levels would in theory be lowered alongside the lower levels of mineralocorticoids (i.e. spironolactone should also produce some degree of antiglucocorticoid effect). In clinical practice however, this has not been found to be the case, as spironolactone has actually been shown to increase cortisol levels, both with acute and chronic administration. Research has shown that this is due to antagonism of the MR, which suppresses negative feedback on the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis positively regulates the secretion of adrenocorticotropic hormone (ACTH), which in turn signals the adrenal glands – the major source of corticosteroid biosynthesis in the body – to increase production of glucocorticoids as well. Therefore, by disinhibiting the regulation on ACTH, its levels rise and spironolactone essentially causes an indirect rise in cortisol production.[45][46] Thus, any antiglucocorticoid activity of spironolactone via direct suppression of glucocorticoid synthesis (at the level of the adrenals) appears to be more than fully offset by its concurrent indirect stimulatory effects on glucocorticoid production secondary to ACTH.
Antiandrogenic[edit]
Spironolactone mediates its antiandrogenic effects via multiple actions, including the following:
Direct blockade of androgens from interacting with the androgen receptor.[47][48] It should be noted however that spironolactone, similarly to other steroidal antiandrogens such as cyproterone acetate, is not a pure, or silent, antagonist of the androgen receptor, but rather a weak partial agonist with the capacity for both agonist and antagonist effects.[49][50][51] However, in the presence of significant enough levels of potent full agonists like testosterone and DHT,[51] the cases in which it is usually used even with regards to the "lower" relative levels present in females, spironolactone will behave similar to a pure antagonist. Nonetheless, there may still be a potential for spironolactone to produce androgenic effects (i.e. act as a receptor agonist) in the body at sufficiently high doses and/or in those with low enough endogenous androgen concentrations. As an example, one condition in which spironolactone is contraindicated is prostate cancer,[52] as the drug has been shown in vitro to significantly accelerate carcinoma growth in the absence of any other androgens, and was found to do so at the relatively high rate of approximately 32%, which was about 35% that of DHT (thus also indicating that its potential intrinsic activity at the androgen receptor may be somewhere around one-third that of endogenous full agonists).[49]
Inhibition of 17α-hydroxylase and 17,20-desmolase, enzymes in the androgen biosynthesis pathway, which in turn results in decreased testosterone and dihydrotestosterone (DHT) levels.[48][53][54][55] Though, its inhibition of these enzymes is said to be relatively weak.[25]
Activation of the progesterone receptor, as, in sufficient amounts, this results in an antigonadotropic effect due to negative feedback on the hypothalamic-pituitary-gonadal axis, which in turn reduces sex steroid production and by extension androgen levels.
Inhibition of 5α-reductase, the enzyme responsible for converting testosterone into the 3- to 10-fold more potent androgen dihydrotestosterone (DHT). However, there is conflicting data on the ability of spironolactone to affect this enzyme. An in vitro study of the effect of spironolactone on prostate tissue 5α-reductase activity found no change even with very high concentrations of the drug.[47] In contrast, another study, after one month of treatment of spironolactone at a dose of 100 mg per day via the oral route, found a significant in vivo inhibitory effect of spironolactone on genital skin 5α-reductase activity in hirsute women as well as an inhibitory effect of the drug on 5α-reductase activity in normal genital skin in vitro, and concluded that spironolactone directly inhibits the 5α-reductase enzyme and that the property could play a role of the beneficial effects of the drug on hirsutism.[56] However, another study of spironolactone in hirsute women, after 6 months of treatment at the same dose (100 mg/d orally), found no significant effects of the drug on the serum ratios of testosterone to DHT and its metabolites—a reliable marker of 5α-reductase activity—whereas significant changes were found with 5 mg per day oral finasteride, a well-established 5α-reductase inhibitor.[57] Finally, yet another study of spironolactone in hirsute women, after 3 months of treatment at a higher dose of 200 mg per day orally, did report significant changes, in the same metabolic markers of 5α-reductase activity.[58] In summation then, whether spironolactone actually inhibits 5α-reductase to some clinical end-point or not and how it may do so remain unclear. It can be deduced from comparison studies, however, that if it does have an effect at reducing hirsutism, it is not as effective as more potent and selective 5α-reductase inhibitors like finasteride. Supporting this conclusion is another trial in which the combination of 100 mg/d spironolactone and 5 mg/d finasteride was found to be significantly more effective than spironolactone alone in the treatment of hirsutism in women.[59]
Acceleration of the rate of metabolism/clearance of testosterone by enhancing the rate of peripheral conversion of testosterone to estradiol.[54]
Progestogenic[edit]
Spironolactone has weak progestogenic properties.[25][60] Its actions in this regard are a result of direct agonist activity at the progesterone receptor, but with a half-maximal potency approximately one tenth that of its activity at the androgen receptor.[38] Spironolactone's progestogenic actions are thought to be responsible for some of its side effects,[61] including the menstrual irregularities seen in women and the undesirable serum lipid profile changes that are seen at higher doses.[24][62][63] They may also serve to augment the gynecomastia caused by the estrogenic effects of spironolactone,[64] as progesterone is known to play a role in breast development.[65]
Estrogenic[edit]
Spironolactone has some indirect estrogenic effects which it mediates via several actions, including the following:
By acting as an antiandrogen, as androgens suppress both estrogen production and action.[48][66]
Displacement of estrogens from sex hormone-binding globulin (SHBG).[53] This occurs because spironolactone binds to SHBG at a relatively high rate, as do endogenous estrogens and androgens, but estrogens like estradiol and estrone are more easily displaced than are androgens like testosterone. As a result, spironolactone blocks relatively more estrogens from interacting with SHBG than androgens, resulting in a higher ratio of free estrogens to free androgens.[67]
Inhibition of the conversion of estradiol to estrone, resulting in an increase in the ratio of estradiol to estrone.[68] This is important because estradiol is approximately 10 times as potent as estrone as an estrogen.[69]
Enhancement of the rate of peripheral conversion of testosterone to estradiol, thus further lowering testosterone levels and increasing estradiol levels.[54]
Pharmacokinetics[edit]
Spironolactone has an onset of action of about 2–3 hours after taking the first dose, with a half-life of about 1–2 hours. Due to its relatively short half-life, it is thought that spironolactone may behave mainly as a prodrug to an array of active metabolites with much longer half-lives (e.g., 12–20 hours in the case of canrenone). Some of its metabolites include canrenone, canrenoic acid, 7α-methylthiospironolactone, and 6β-hydroxy-7α-methylthiospironolactone, among many others. The drug is highly plasma protein bound. It is metabolized by the liver, from which it is partially eliminated with the majority being handled by the kidneys. Minimal amounts are handled by biliary excretion.[1]
Of note, the clinical benefits of the drug when used a diuretic are typically not seen until 2–3 days after dosing begins, perhaps accounted for by the need for 4-5 doses before reaching a steady state concentration. Likewise, the maximal antihypertensive effective may not be seen for 2–3 weeks.
The bioavailability of spironolactone improves significantly when it is taken with food.[70][71]
Spironolactone bodies[edit]
Micrograph of an adrenal gland spironolactone bodies. H&E stain.
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.[72]
No comments:
Post a Comment