Toremifene
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Toremifene, sold under the brand name Fareston among others, is a medication which is used in the treatment of
advanced breast cancer Metastatic breast cancer, also referred to as metastases, advanced breast cancer, secondary tumors, secondaries or stage IV breast cancer, is a stage of breast cancer where the breast cancer cells have spread to distant sites beyond the axillary l ...
in
postmenopausal Menopause, also known as the climacteric, is the time in women's lives when menstrual periods stop permanently, and they are no longer able to bear children. Menopause usually occurs between the age of 47 and 54. Medical professionals often d ...
women.https://www.accessdata.fda.gov/drugsatfda_docs/label/2011/020497s006lbl.pdf It is taken
by mouth Oral administration is a route of administration where a substance is taken through the mouth. Per os abbreviated to P.O. is sometimes used as a direction for medication to be taken orally. Many medications are taken orally because they are i ...
.
Side effect In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...
s of toremifene include
hot flash Hot flashes (also known as hot flushes) are a form of flushing, often caused by the changing hormone levels that are characteristic of menopause. They are typically experienced as a feeling of intense heat with sweating and rapid heartbeat, and ...
es, sweating,
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
,
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteri ...
,
dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness. Dizziness is a common medical c ...
,
vaginal discharge Vaginal discharge is a mixture of liquid, cells, and bacteria that lubricate and protect the vagina. This mixture is constantly produced by the cells of the vagina and cervix, and it exits the body through the vaginal opening. The composition, amou ...
, and
vaginal bleeding Vaginal bleeding is any expulsion of blood from the vagina. This bleeding may originate from the uterus, vaginal wall, or cervix. Generally, it is either part of a normal menstrual cycle or is caused by hormonal or other problems of the reproductiv ...
. It can also cause
blood clot A thrombus (plural thrombi), colloquially called a blood clot, is the final product of the blood coagulation step in hemostasis. There are two components to a thrombus: aggregated platelets and red blood cells that form a plug, and a mesh of ...
s,
irregular heartbeat Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults ...
,
cataract A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...
s, visual disturbances,
elevated liver enzymes In medicine, the presence of elevated transaminases, commonly the transaminases alanine transaminase (ALT) and aspartate transaminase (AST), may be an indicator of liver dysfunction. Other terms include transaminasemia, transaminitis, and elevated ...
,
endometrial hyperplasia Endometrial hyperplasia is a condition of excessive proliferation of the cells of the endometrium, or inner lining of the uterus. Most cases of endometrial hyperplasia result from high levels of estrogens, combined with insufficient levels of t ...
, and endometrial cancer. High blood calcium levels can occur in women with
bone metastases Bone metastasis, or osseous metastatic disease, is a category of cancer metastases that results from primary tumor invasion to bone. Bone-originating primary tumors such as osteosarcoma, chondrosarcoma, and Ewing's sarcoma are rare; the most common ...
. The medication is a
selective estrogen receptor modulator Selective estrogen receptor modulators (SERMs), also known as estrogen receptor agonist/antagonists (ERAAs), are a class of drugs that act on the estrogen receptor (ER). A characteristic that distinguishes these substances from pure ER agonists a ...
(SERM) and hence is a mixed
agonist An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the ago ...
antagonist An antagonist is a character in a story who is presented as the chief foe of the protagonist. Etymology The English word antagonist comes from the Greek ἀνταγωνιστής – ''antagonistēs'', "opponent, competitor, villain, enemy, riv ...
of the
estrogen receptor Estrogen receptors (ERs) are a group of proteins found inside cells. They are receptors that are activated by the hormone estrogen ( 17β-estradiol). Two classes of ER exist: nuclear estrogen receptors (ERα and ERβ), which are members of the ...
(ER), the
biological target A biological target is anything within a living organism to which some other entity (like an endogenous ligand or a drug) is directed and/or binds, resulting in a change in its behavior or function. Examples of common classes of biological targets ...
of
estrogen Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal acti ...
s like
estradiol Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous and menstrual female reproductive cycles. Estradiol is responsible for the development of f ...
. It has
estrogen Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal acti ...
ic effects in
bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...
, the
liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...
, and the
uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The uter ...
and
antiestrogen Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or ...
ic effects in the
breast The breast is one of two prominences located on the upper ventral region of a primate's torso. Both females and males develop breasts from the same embryological tissues. In females, it serves as the mammary gland, which produces and secret ...
s. It is a
triphenylethylene Triphenylethylene (TPE) is a simple aromatic hydrocarbon that possesses weak estrogenic activity. Its estrogenic effects were discovered in 1937. TPE was derived from structural modification of the more potent estrogen diethylstilbestrol, which is ...
derivative In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. F ...
and is closely related to
tamoxifen Tamoxifen, sold under the brand name Nolvadex among others, is a selective estrogen receptor modulator used to prevent breast cancer in women and treat breast cancer in women and men. It is also being studied for other types of cancer. It has b ...
. Toremifene was introduced for medical use in 1997. It was the first
antiestrogen Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or ...
to be introduced since tamoxifen in 1978. It is available as a
generic medication A generic drug is a pharmaceutical drug that contains the same chemical substance as a drug that was originally protected by chemical patents. Generic drugs are allowed for sale after the patents on the original drugs expire. Because the active ch ...
in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
.


Medical uses

Toremifene is approved for the treatment of
metastatic breast cancer Metastatic breast cancer, also referred to as metastases, advanced breast cancer, secondary tumors, secondaries or stage IV breast cancer, is a stage of breast cancer where the breast cancer cells have spread to distant sites beyond the axillary l ...
in postmenopausal women with estrogen receptor-positive or unknown-status
tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
s. This is its only approved use in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
. It shows equivalent effectiveness to tamoxifen for this indication. Toremifene has been found to be effective in the treatment of breast pain and may be a more effective medication than tamoxifen for this indication. It also has superior effects on
bone mineral density Bone density, or bone mineral density, is the amount of bone mineral in bone tissue. The concept is of mass of mineral per volume of bone (relating to density in the physics sense), although clinically it is measured by proxy according to optica ...
and
lipid profile A lipid profile or lipid panel is a panel of blood tests used to find abnormalities in lipids, such as cholesterol and triglycerides. The results of this test can identify certain genetic diseases and can determine approximate risks for cardiovas ...
, including levels of
cholesterol Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell mem ...
and
triglyceride A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''wikt:tri-#Prefix, tri-'' and ''glyceride''). Triglycerides are the main constituents of body fat in humans and other ...
s, compared to tamoxifen. Toremifene has been reported to significantly improve symptoms of
gynecomastia Gynecomastia (also spelled gynaecomastia) is the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue as a result of a hormone imbalance between estrogens and androgens. Updated by Brent Wisse ( ...
in men.


Available forms

Toremifene is provided in the form of 60 mg
oral The word oral may refer to: Relating to the mouth * Relating to the mouth, the first portion of the alimentary canal that primarily receives food and liquid **Oral administration of medicines ** Oral examination (also known as an oral exam or or ...
tablets.


Side effects

The
side effect In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...
s of toremifene are similar to those of tamoxifen. The most common side effect is
hot flash Hot flashes (also known as hot flushes) are a form of flushing, often caused by the changing hormone levels that are characteristic of menopause. They are typically experienced as a feeling of intense heat with sweating and rapid heartbeat, and ...
es. Other side effects include sweating,
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
,
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteri ...
,
dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness. Dizziness is a common medical c ...
,
vaginal discharge Vaginal discharge is a mixture of liquid, cells, and bacteria that lubricate and protect the vagina. This mixture is constantly produced by the cells of the vagina and cervix, and it exits the body through the vaginal opening. The composition, amou ...
, and
vaginal bleeding Vaginal bleeding is any expulsion of blood from the vagina. This bleeding may originate from the uterus, vaginal wall, or cervix. Generally, it is either part of a normal menstrual cycle or is caused by hormonal or other problems of the reproductiv ...
. In women with
bone metastases Bone metastasis, or osseous metastatic disease, is a category of cancer metastases that results from primary tumor invasion to bone. Bone-originating primary tumors such as osteosarcoma, chondrosarcoma, and Ewing's sarcoma are rare; the most common ...
, hypercalcemia may occur. Toremifene has a small risk of thromboembolic events.
Cataract A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...
s,
vision changes A vision disorder is an impairment of the sense of vision. Vision disorder is not the same as an eye disease. Although many vision disorders do have their immediate cause in the eye, there are many other causes that may occur at other locations in ...
, and elevation of liver enzymes have been reported. The drug prolongs the QT interval and hence has a risk of potentially fatal dysrhythmias. The risk of dysrhythmias can be reduced by avoiding use in patients with
hypokalemia Hypokalemia is a low level of potassium (K+) in the blood serum. Mild low potassium does not typically cause symptoms. Symptoms may include feeling tired, leg cramps, weakness, and constipation. Low potassium also increases the risk of an abno ...
,
hypomagnesemia Magnesium deficiency is an electrolyte disturbance in which there is a low level of magnesium in the body. It can result in multiple symptoms. Symptoms include tremor, poor coordination, muscle spasms, loss of appetite, personality changes, an ...
, pre-existing QT prolongation, and in those taking other QT-prolonging drugs. Because toremifene has
estrogen Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal acti ...
ic actions in the
uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The uter ...
, it can increase the risk of
endometrial hyperplasia Endometrial hyperplasia is a condition of excessive proliferation of the cells of the endometrium, or inner lining of the uterus. Most cases of endometrial hyperplasia result from high levels of estrogens, combined with insufficient levels of t ...
and endometrial cancer. Toremifene appears to be safer than tamoxifen. It has a lower risk of
venous thromboembolism Venous thrombosis is blockage of a vein caused by a thrombus (blood clot). A common form of venous thrombosis is deep vein thrombosis (DVT), when a blood clot forms in the deep veins. If a thrombus breaks off (embolizes) and flows to the lungs to ...
(VTE) (e.g.,
pulmonary embolism Pulmonary embolism (PE) is a blockage of an pulmonary artery, artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism). Symptoms of a PE may include dyspnea, shortness of breath, chest pain p ...
),
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
, and
cataract A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...
s. The lower risk of VTE may be related to the fact tamoxifen decreases levels of the antithrombin III to a significantly greater extent than either 60 or 200 mg/day toremifene.


Interactions

Toremifene is a substrate of
CYP3A4 Cytochrome P450 3A4 (abbreviated CYP3A4) () is an important enzyme in the body, mainly found in the liver and in the intestine. It oxidizes small foreign organic molecules (xenobiotics), such as toxins or drugs, so that they can be removed from t ...
, a
cytochrome P450 Cytochromes P450 (CYPs) are a Protein superfamily, superfamily of enzymes containing heme as a cofactor (biochemistry), cofactor that functions as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are ...
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
, and hence drugs that induce or
inhibit Inhibitor or inhibition may refer to: In biology * Enzyme inhibitor, a substance that binds to an enzyme and decreases the enzyme's activity * Reuptake inhibitor, a substance that increases neurotransmission by blocking the reuptake of a neurotr ...
this enzyme can respectively decrease or increase levels of toremifene in the body.


Pharmacology


Pharmacodynamics

Toremifene is a
selective estrogen receptor modulator Selective estrogen receptor modulators (SERMs), also known as estrogen receptor agonist/antagonists (ERAAs), are a class of drugs that act on the estrogen receptor (ER). A characteristic that distinguishes these substances from pure ER agonists a ...
(SERM). That is, it is a selective mixed
agonist–antagonist In pharmacology the term agonist-antagonist or mixed agonist/antagonist is used to refer to a drug which under some conditions behaves as an agonist (a substance that fully activates the receptor that it binds to) while under other conditions, beh ...
of the
estrogen receptor Estrogen receptors (ERs) are a group of proteins found inside cells. They are receptors that are activated by the hormone estrogen ( 17β-estradiol). Two classes of ER exist: nuclear estrogen receptors (ERα and ERβ), which are members of the ...
s (ERs), with
estrogen Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal acti ...
ic actions in some tissues and
antiestrogen Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or ...
ic actions in other tissues. The medication has estrogenic effects in
bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...
,
partial Partial may refer to: Mathematics * Partial derivative, derivative with respect to one of several variables of a function, with the other variables held constant ** ∂, a symbol that can denote a partial derivative, sometimes pronounced "partial ...
estrogenic effects in the
uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The uter ...
and
liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...
, and antiestrogenic effects in the
breast The breast is one of two prominences located on the upper ventral region of a primate's torso. Both females and males develop breasts from the same embryological tissues. In females, it serves as the mammary gland, which produces and secret ...
s. The
affinity Affinity may refer to: Commerce, finance and law * Affinity (law), kinship by marriage * Affinity analysis, a market research and business management technique * Affinity Credit Union, a Saskatchewan-based credit union * Affinity Equity Par ...
of toremifene for the ER is similar to that of tamoxifen. In studies using rat ER, toremifene had about 1.4% and tamoxifen had about 1.6% of the affinity of
estradiol Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous and menstrual female reproductive cycles. Estradiol is responsible for the development of f ...
for the ER. The affinities (Ki) of toremifene at the human ERs have been reported as 20.3 ± 0.1 nM for the
ERα Estrogen receptor alpha (ERα), also known as NR3A1 (nuclear receptor subfamily 3, group A, member 1), is one of two main types of estrogen receptor, a nuclear receptor (mainly found as a chromatin-binding protein) that is activated by the sex ...
and 15.4 ± 3.1 nM for the
ERβ Estrogen receptor beta (ERβ) also known as NR3A2 (nuclear receptor subfamily 3, group A, member 2) is one of two main types of estrogen receptor—a nuclear receptor which is activated by the sex hormone estrogen. In humans ERβ is encoded by ...
. In other rat ER studies, toremifene had 3–9% of the affinity of estradiol for the ER while its
metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...
s ''N''-desmethyltoremifene and 4-hydroxytoremifene had 3–5% and 64–158% of the affinity of estradiol for the ER, respectively. The affinity of another metabolite, 4-hydroxy-''N''-desmethyltoremifene, was not assessed. 4-Hydroxytoremifene showed about 100-fold higher antiestrogenic
potency Potency may refer to: * Potency (pharmacology), a measure of the activity of a drug in a biological system * Virility * Cell potency, a measure of the differentiation potential of stem cells * In homeopathic dilutions, potency is a measure of how ...
than toremifene ''
in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology an ...
'' in one study, but not in another. 4-Hydroxy-''N''-desmethyltoremifene has also been found to be strongly antiestrogenic ''in vitro''. The metabolites of toremifene, particularly 4-hydroxytoremifene, may contribute importantly to the clinical activity of the medication. On the other hand, some authorities consider toremifene not to be a prodrug. Toremifene is very similar to
tamoxifen Tamoxifen, sold under the brand name Nolvadex among others, is a selective estrogen receptor modulator used to prevent breast cancer in women and treat breast cancer in women and men. It is also being studied for other types of cancer. It has b ...
and shares most of its properties. There are some indications that toremifene may be safer than tamoxifen as it is not a hepatocarcinogen in animals and may have less potential for
genotoxicity Genotoxicity is the property of chemical agents that damage the genetic information within a cell causing mutations, which may lead to cancer. While genotoxicity is often confused with mutagenicity, all mutagens are genotoxic, but some genotoxic su ...
. However, clinical studies have found no significant differences between toremifene and tamoxifen, including in terms of
effectiveness Effectiveness is the capability of producing a desired result or the ability to produce desired output. When something is deemed effective, it means it has an intended or expected outcome, or produces a deep, vivid impression. Etymology The ori ...
,
tolerability Tolerability refers to the degree to which overt adverse effects of a drug can be tolerated by a patient. Tolerability of a particular drug can be discussed in a general sense, or it can be a quantifiable measurement as part of a clinical study. U ...
, and
safety Safety is the state of being "safe", the condition of being protected from harm or other danger. Safety can also refer to risk management, the control of recognized hazards in order to achieve an acceptable level of risk. Meanings There are ...
, and hence the clinical use of toremifene has been somewhat limited. Toremifene is thought to have about one-third of the
potency Potency may refer to: * Potency (pharmacology), a measure of the activity of a drug in a biological system * Virility * Cell potency, a measure of the differentiation potential of stem cells * In homeopathic dilutions, potency is a measure of how ...
of tamoxifen; i.e., 60 mg toremifene is roughly equivalent to 20 mg tamoxifen in the treatment of breast cancer. Toremifene has been found to have antigonadotropic effects in postmenopausal women, progonadotropic effects in men, to increase
sex hormone-binding globulin Sex hormone-binding globulin (SHBG) or sex steroid-binding globulin (SSBG) is a glycoprotein that binds to androgens and estrogens. When produced by the Sertoli cells in the seminiferous tubules of the testis, it has also been called androgen ...
levels, and to decrease
insulin-like growth factor 1 Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone similar in molecular structure to insulin which plays an important role in childhood growth, and has anabolic effects in adults. IGF-1 is a protein that in humans is ...
levels by about 20% in postmenopausal women and men. In addition to its activity as a SERM, 4-hydroxytoremifene is an antagonist of the
estrogen-related receptor γ Estrogen-related receptor gamma (ERR-gamma), also known as NR3B3 (nuclear receptor subfamily 3, group B, member 3), is a nuclear receptor that in humans is encoded by the ESRRG (EStrogen Related Receptor Gamma) gene. It behaves as a constitutive ...
(ERRγ).


Pharmacokinetics


Absorption

The
bioavailability In pharmacology, bioavailability is a subcategory of absorption and is the fraction (%) of an administered drug that reaches the systemic circulation. By definition, when a medication is administered intravenously, its bioavailability is 100%. Ho ...
of toremifene has not been precisely determined but is known to be good and has been estimated to be approximately 100%. Levels of toremifene at
steady state In systems theory, a system or a process is in a steady state if the variables (called state variables) which define the behavior of the system or the process are unchanging in time. In continuous time, this means that for those properties ''p' ...
with a dosage of 60 mg/day are 800 to 879 ng/mL. Levels of ''N''-desmethyltoremifene at steady state with toremifene were 3,058 ng/mL at 60 mg/day, 5,942 ng/mL at 200 mg/day, and 11,913 ng/mL at 400 mg/day. Levels of 4-hydroxytoremifene at steady state with toremifene were 438 ng/mL at 200 mg/day and 889 ng/mL at 400 mg/day. Concentrations of toremifene increase linearly across a dose range of 10 to 680 mg.


Distribution

Toremifene is 99.7% bound to plasma proteins, with 92% bound specifically to
albumin Albumin is a family of globular proteins, the most common of which are the serum albumins. All the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins ...
, about 6% to β1 globulin fraction, and about 2% to a fraction between albumin and α1 globulins. The apparent
volume of distribution In pharmacology, the volume of distribution (VD, also known as apparent volume of distribution, literally, ''volume of dilution'') is the theoretical volume that would be necessary to contain the total amount of an administered drug at the same c ...
of toremifene ranged from 457 to 958 L.


Metabolism

Toremifene is
metabolized Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
in the
liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...
primarily by
CYP3A4 Cytochrome P450 3A4 (abbreviated CYP3A4) () is an important enzyme in the body, mainly found in the liver and in the intestine. It oxidizes small foreign organic molecules (xenobiotics), such as toxins or drugs, so that they can be removed from t ...
and then undergoes secondary
hydroxylation In chemistry, hydroxylation can refer to: *(i) most commonly, hydroxylation describes a chemical process that introduces a hydroxyl group () into an organic compound. *(ii) the ''degree of hydroxylation'' refers to the number of OH groups in a ...
. The
metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...
s of toremifene include ''N''-desmethyltoremifene, 4-hydroxytoremifene, and 4-hydroxy-''N''-desmethyltoremifene, among others.
Ospemifene Ospemifene (brand names Osphena and Senshio produced by Shionogi) is an oral medication indicated for the treatment of dyspareuniapain during sexual intercourseencountered by some women, more often in those who are post-menopausal. Ospemifene is ...
(deaminohydroxytoremifene) is also a major metabolite of toremifene.https://www.accessdata.fda.gov/drugsatfda_docs/label/2011/020497s006lbl.pdf


Elimination

The
elimination half-life Biological half-life (also known as elimination half-life, pharmacologic half-life) is the time taken for concentration of a biological substance (such as a medication) to decrease from its maximum concentration ( Cmax) to half of Cmax in the bl ...
of toremifene is 3 to 7 days in healthy individuals. In people with impaired liver function, the half-life is 11 days. The elimination half-lives of the metabolites of toremifene are 5 to 21 days for ''N''-desmethyltoremifene, 5 days for 4-hydroxytoremifene, and 4 days for ospemifene. The long elimination half-lives of toremifene and its metabolites are thought to be due to
enterohepatic recirculation Enterohepatic circulation refers to the circulation of biliary acids, bilirubin, drugs or other substances from the liver to the bile, followed by entry into the small intestine, absorption by the enterocyte and transport back to the liver. E ...
and high plasma protein binding. Toremifene is eliminated 70% in the feces, as metabolites.


Chemistry

Toremifene, also known as ''4-chlorotamoxifen'', is a
derivative In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. F ...
of
triphenylethylene Triphenylethylene (TPE) is a simple aromatic hydrocarbon that possesses weak estrogenic activity. Its estrogenic effects were discovered in 1937. TPE was derived from structural modification of the more potent estrogen diethylstilbestrol, which is ...
and a close analogue of
tamoxifen Tamoxifen, sold under the brand name Nolvadex among others, is a selective estrogen receptor modulator used to prevent breast cancer in women and treat breast cancer in women and men. It is also being studied for other types of cancer. It has b ...
. It is also closely related to afimoxifene (4-hydroxytamoxifen) and
ospemifene Ospemifene (brand names Osphena and Senshio produced by Shionogi) is an oral medication indicated for the treatment of dyspareuniapain during sexual intercourseencountered by some women, more often in those who are post-menopausal. Ospemifene is ...
(deaminohydroxytoremifene).


History

Toremifene was introduced in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
in 1997. It was the first
antiestrogen Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or ...
to be introduced in this country since tamoxifen in 1978.


Society and culture


Generic names

''Toremifene'' is the generic name of the drug and its and , while ''toremifene citrate'' is its and and ''torémifène'' is its .


Brand names

Toremifene is marketed almost exclusively under the brand name Fareston.


Availability

Toremifene is marketed widely throughout the world and is available in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
,
Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...
, many other
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
an countries,
South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...
,
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
,
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
, and elsewhere throughout the world.


Research

Toremifene was also evaluated for prevention of prostate cancer and had the tentative brand name Acapodene. In 2007 the pharmaceutical company GTx, Inc was conducting two different phase 3
clinical trial Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, dietar ...
s; First, a pivotal Phase clinical trial for the treatment of serious side effects of
androgen deprivation therapy Androgen deprivation therapy (ADT), also called androgen suppression therapy, is an antihormone therapy whose main use is in treating prostate cancer. Prostate cancer cells usually require androgen hormones, such as testosterone, to grow. ADT red ...
(ADT) (especially vertebral/spine fractures and
hot flashes Hot flashes (also known as hot flushes) are a form of flushing, often caused by the changing hormone levels that are characteristic of menopause. They are typically experienced as a feeling of intense heat with sweating and rapid heartbeat, and ...
, lipid profile, and
gynecomastia Gynecomastia (also spelled gynaecomastia) is the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue as a result of a hormone imbalance between estrogens and androgens. Updated by Brent Wisse ( ...
) for advanced prostate cancer, and second, a pivotal Phase III clinical trial for the prevention of prostate cancer in high risk men with high grade prostatic intraepithelial neoplasia, or PIN. Results of these trials are expected by first quarter of 2008 An NDA for the first application (relief of prostate cancer ADT side effects) was submitted in Feb 2009, and in Oct 2009 the FDA said they would need more clinical data, e.g. another phase III trial. Ultimately, development was discontinued and toremifene was never marketed for complications associated with ADT or the treatment or prevention of prostate cancer. Toremifene may be useful in the prevention of
bicalutamide Bicalutamide, sold under the brand name Casodex among others, is an antiandrogen medication that is primarily used to treat prostate cancer. It is typically used together with a gonadotropin-releasing hormone (GnRH) analogue or surgical remo ...
-induced gynecomastia.


Phase III Trial Results

A double-blind, placebo-controlled, randomized, 3 year clinical trial of toremifene was conducted using a sample of 1,260 men. Subjects had a median age of 64 years and were diagnosed with high-grade prostatic intraepithelial neoplasia (HGPIN), which is considered premalignant, though Thompson and Leach feel a low grade PIN could also be deemed premalignant. The sponsor, GTx, who designed and managed the study, found 34.7% of the placebo and 32.3% of the toremifene groups had cancer events. No distinction was found in
Gleason score The Gleason grading system is used to help evaluate the prognosis of men with prostate cancer using samples from a prostate biopsy. Together with other parameters, it is incorporated into a strategy of prostate cancer staging which predicts prog ...
s of either group. Previous murine studies using transgenic adenocarcinoma of mouse prostate (TRAMP) mice showed toremifene prevented palpable tumors in 60% of the animals. This study used toremifene as an early prophylactic, which differentiates it from the phase III human studies.Raghow, S., Hooshdaran, M. Z., Katiyar, S., and Steiner, M. S., Toremifene prevents prostate cancer in the transgenic adenocarcinoma of mouse prostate model. ''Cancer Research'' 2002;62:1370-6. http://cancerres.aacrjournals.org/content/62/5/1370= Retrieved 31 July 2019


References


Further reading

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External links


Toremifene - AdisInsight
{{Estrogen receptor modulators Dimethylamino compounds Hepatotoxins Hormonal antineoplastic drugs Organochlorides Phenol ethers Prodrugs Progonadotropins Selective estrogen receptor modulators Triphenylethylenes World Anti-Doping Agency prohibited substances