Clomifene, also known as clomiphene, is a medication used to treat

infertility Infertility is the inability of a person, animal or plant to reproduce by natural means. It is usually not the natural state of a healthy adult, except notably among certain eusocial species (mostly haplodiploid insects). It is the normal state ...

in women who do not ovulate, including those with

polycystic ovary syndrome Polycystic ovary syndrome, or PCOS, is the most common endocrine disorder in women of reproductive age. The syndrome is named after the characteristic cysts which may form on the ovaries, though it is important to note that this is a sign and no ...

. Use results in a greater chance of

twins Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...

. It is taken by mouth once a day, with a course of treatment that usually lasts for five days. Common side effects include

pelvic pain Pelvic pain is pain in the area of the pelvis. Acute pain is more common than chronic pain. If the pain lasts for more than six months, it is deemed to be chronic pelvic pain. It can affect both the male and female pelvis. Common causes in include ...

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 ...

. Other side effects can include changes in vision, vomiting, trouble sleeping,

ovarian cancer Ovarian cancer is a cancerous tumor of an ovary. It may originate from the ovary itself or more commonly from communicating nearby structures such as fallopian tubes or the inner lining of the abdomen. The ovary is made up of three different c ...

, and

seizures An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or neural oscillation, synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much o ...

. It is not recommended in people with

liver disease Liver disease, or hepatic disease, is any of many diseases of the liver. If long-lasting it is termed chronic liver disease. Although the diseases differ in detail, liver diseases often have features in common. Signs and symptoms Some of the sig ...

abnormal 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 reprod ...

of unknown cause or who are

pregnant Pregnancy is the time during which one or more offspring develops (gestation, gestates) inside a woman, woman's uterus (womb). A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occur ...

. Clomifene is in the

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) family of medication and is a nonsteroidal medication. It works by causing the release of

GnRH Gonadotropin-releasing hormone (GnRH) is a releasing hormone responsible for the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. GnRH is a tropic peptide hormone synthesized and releas ...

by the

hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...

, and subsequently

gonadotropin Gonadotropins are glycoprotein hormones secreted by gonadotropic cells of the anterior pituitary of vertebrates. This family includes the mammalian hormones follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the placental/ chorioni ...

from the

anterior pituitary A major organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior) is the glandular, anterior lobe that together with the posterior lobe (posterior pituitary, or the neurohypophysis) makes up the p ...

. Clomifene was approved for medical use in the United States in 1967. It is on the

World Health Organization's List of Essential Medicines The WHO Model List of Essential Medicines (aka Essential Medicines List or EML), published by the World Health Organization (WHO), contains the medications considered to be most effective and safe to meet the most important needs in a health ...

, under the category "Ovulation inducers" (Complementary List). Its introduction began the era of assisted reproductive technology. Clomifene (particularly the purified enclomiphene isomer) has also been found to have a powerful ability to boost or restore testosterone levels in hypogonadal men.

Medical uses

Ovulation induction

Clomifene is one of several alternatives for

ovulation induction Ovulation induction is the stimulation of ovulation by medication. It is usually used in the sense of stimulation of the development of ovarian follicles Ovulation Induction Retrieved on Mars 7, 2010 to reverse anovulation or oligoovulation. S ...

in those who are infertile due to

anovulation Anovulation is when the ovaries do not release an oocyte during a menstrual cycle. Therefore, ovulation does not take place. However, a woman who does not ovulate at each menstrual cycle is not necessarily going through menopause. Chronic anovula ...

oligoovulation Ovulation is the release of egg cells, eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells. After ovulation, during the luteal phase, the egg will be available to be ...

. Evidence is lacking for the use of clomifene in those who are infertile without a known reason. In such cases, studies have observed a clinical pregnancy rate 5.6% per cycle with clomifene treatment vs. 1.3%–4.2% per cycle without treatment. Proper timing of the drug is important; it should be taken starting on about the fifth day of the cycle, and there should be frequent intercourse. The following procedures may be used to monitor induced cycles: * Follicular monitoring with

vaginal ultrasound Vaginal ultrasonography is a medical ultrasonography that applies an ultrasound transducer (or "probe") in the vagina to visualize organs within the pelvic cavity. It is also called transvaginal ultrasonography because the ultrasound waves go ''a ...

, starting 4–6 days after the last pill. Serial transvaginal ultrasound can reveal the size and number of developing follicles. It can also provide presumptive evidence of ovulation such as the sudden collapse of the preovulatory follicle, and an increase in fluid volume in the

rectouterine pouch The rectouterine pouch (recto-uterine pouch), pouch of Douglas, or rectovaginal pouch is the extension of the peritoneum between the rectum and the posterior wall of the uterus in the human female. Its anterior boundary is formed by the posterior ...

. After ovulation, it may reveal signs of luteinization such as loss of clearly defined follicular margins and appearance of internal echoes. * Serum

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 ...

levels, starting 4–6 days after the last pill * Adequacy of LH surge by urine

LH surge Luteinizing hormone (LH, also known as luteinising hormone, lutropin and sometimes lutrophin) is a hormone produced by gonadotropic cells in the anterior pituitary gland. The production of LH is regulated by gonadotropin-releasing hormone (GnRH) ...

tests 3 to 4 days after last clomifene pill * Post-coital test 1–3 days before ovulation to check whether there are at least 5 progressive sperm per HPF * Mid-luteal progesterone, with at least 10 ng/ml 7–9 days after ovulation being regarded as adequate. Repeat dosing: This 5-day treatment course can be repeated every 30 days. The dosage may be increased by 50-mg increments in subsequent cycles until ovulation is achieved. It is not recommended by the manufacturer to use clomifene for more than 6 cycles. It is no longer recommended to perform an ultrasound examination to exclude any significant residual ovarian enlargement before each new treatment cycle.

Other uses

Clomifene has also been used with other assisted reproductive technology to increase success rates of these other modalities. Clomifene is sometimes used in the treatment of male

hypogonadism Hypogonadism means diminished functional activity of the gonads—the testes or the ovaries—that may result in diminished production of sex hormones. Low androgen (e.g., testosterone) levels are referred to as hypoandrogenism and low estrogen ...

as an alternative to

testosterone replacement therapy Androgen replacement therapy (ART), often referred to as testosterone replacement therapy (TRT) or hormone replacement therapy (HRT), is a form of hormone therapy in which androgens, often testosterone, are supplemented or replaced exogenously ...

. The medication has been used at a dosage of 20 to 50 mg three times per week to once daily for this indication. It has been found to increase testosterone levels by 2- to 2.5-times in hypogonadal men at such dosages. Despite the use of questionnaires in testosterone replacement comparator trials being called into question, clomifene's lower cost, therapeutic benefits, and greater value towards hypogonadism improvement have been noted. Clomifene consists of two

stereoisomers In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in ...

in equal proportion:

enclomifene Enclomifene (), or enclomiphene (), a nonsteroidal selective estrogen receptor modulator of the triphenylethylene group acts by antagonizing the estrogen receptor (ER) in the pituitary gland, which reduces negative feedback by estrogen on the h ...

and zuclomifene. Zuclomifene has pro-estrogenic properties, whereas enclomifene is pro-androgenic, i.e. it promotes testosterone production through stimulation of the

HPG axis HPG may refer to: * Huppuguda railway station, in Hyderabad, India * Hypothalamic–pituitary–gonadal axis * People's Defence Forces (Kurdish: '), the armed wing of the Kurdistan Workers' Party * Shennongjia Hongping Airport, in Hubei, China * ...

. For this reason, purified enclomifene isomer has been found to be twice as effective in boosting testosterone compared to the standard mix of both isomers. Additionally, enclomifene has a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...

of just 10 hours, but zuclomifene has a half-life of 30 days—therefore if the goal is to boost testosterone, taking regular clomifene may produce far longer-lasting pro-estrogenic effects than pro-androgenic effects. Clomifene has been used in the treatment 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 (1 ...

. It has been found to be useful in the treatment of some cases of gynecomastia but it is not as effective as

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 ...

raloxifene Raloxifene, sold under the brand name Evista among others, is a medication used to prevent and treat osteoporosis in postmenopausal women and those on glucocorticoids. For osteoporosis it is less preferred than bisphosphonates. It is also used to ...

for this indication. It has shown variable results for gynecomastia (probably because the zuclomifene isomer is estrogenic), and hence is not recommended for treatment of the condition. Pure enclomifene isomer is likely to be more effective than clomifene at treating gynecomastia, because of the lack of the zuclomifene isomer (as noted above). Due to its long half-life, zuclomifene can be detected in urine for at least 261 days after discontinuation (261 days after discontinuation with a half-life of 30 days, there is still 0.24% of the peak level of zuclomifene being excreted, whereas with a half-life of 10 hours, enclomifene reaches the same 0.24% level in less than 4 days). Because of its potential for boosting testosterone, clomifene is listed as banned for use by competitive sportsmen, both in and out of competition, by the

World Anti-Doping Agency The World Anti-Doping Agency (WADA; french: Agence mondiale antidopage, AMA) is a foundation initiated by the International Olympic Committee based in Canada to promote, coordinate, and monitor the fight against drugs in sports. The agency's key ...

, absent an organic etiology of

primary hypogonadism Hypergonadotropic hypogonadism (HH), also known as primary or peripheral/gonadal hypogonadism or primary gonadal failure, is a condition which is characterized by hypogonadism which is due to an impaired response of the gonads to the gonadotropins ...

Contraindications

Contraindications include an allergy to the medication, pregnancy, prior liver problems, abnormal vaginal bleeding of unclear cause, ovarian cysts other than those due to polycystic ovarian syndrome, unmanaged adrenal or thyroid problems, and

pituitary tumors Pituitary adenomas are tumors that occur in the pituitary gland. Most pituitary tumors are benign, approximately 35% are invasive and just 0.1% to 0.2% are carcinomas.adverse drug reaction An adverse drug reaction (ADR) is a harmful, unintended result caused by taking medication. ADRs may occur following a single dose or prolonged administration of a drug or result from the combination of two or more drugs. The meaning of this term ...

associated with the use of clomifene (>10% of people) is reversible ovarian enlargement. Less common effects (1–10% of people) include visual symptoms (blurred vision,

double vision Diplopia is the simultaneous perception of two images of a single object that may be displaced horizontally or vertically in relation to each other. Also called double vision, it is a loss of visual focus under regular conditions, and is often v ...

, floaters, eye sensitivity to light, scotomata), headaches, vasomotor flushes (or

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), light sensitivity and pupil constriction, abnormal uterine bleeding and/or abdominal discomfort. Rare adverse events (<1% of people) include: high blood level of triglycerides, liver inflammation, reversible baldness and/or

ovarian hyperstimulation syndrome Ovarian hyperstimulation syndrome (OHSS) is a medical condition that can occur in some women who take fertility medication to stimulate egg growth, and in other women in very rare cases. Most cases are mild, but rarely the condition is severe and c ...

. Clomifene can lead to multiple ovulation, hence increasing the chance of

twin Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...

s (10% of births instead of ~1% in the general population) and

triplets A multiple birth is the culmination of one multiple pregnancy, wherein the mother gives birth to two or more babies. A term most applicable to vertebrate species, multiple births occur in most kinds of mammals, with varying frequencies. Such bir ...

. Rates of birth defects and miscarriages do not appear to change with the use of clomifene for fertility. Clomifene has been associated with liver abnormalities and a couple of cases of

hepatotoxicity Hepatotoxicity (from ''hepatic toxicity'') implies chemical-driven liver damage. Drug-induced liver injury is a cause of acute and chronic liver disease caused specifically by medications and the most common reason for a drug to be withdrawn fro ...

Cancer risk

Some studies have suggested that clomifene if used for more than a year may increase the risk of

. This may only be the case in those who have never been and do not become pregnant. Subsequent studies have failed to support those findings. Clomifene has been shown to be associated with an increased risk of malignant

melanoma Melanoma, also redundantly known as malignant melanoma, is a type of skin cancer that develops from the pigment-producing cells known as melanocytes. Melanomas typically occur in the skin, but may rarely occur in the mouth, intestines, or eye ( ...

s and

thyroid cancer Thyroid cancer is cancer that develops from the tissues of the thyroid gland. It is a disease in which cells grow abnormally and have the potential to spread to other parts of the body. Symptoms can include swelling or a lump in the neck. C ...

. Thyroid cancer risk was not associated with the number of pregnancies carried to viability.

Pharmacology

Pharmacodynamics

Selective estrogen receptor modulator activity

Clomifene is a

nonsteroidal A nonsteroidal compound is a drug that is not a steroid nor a steroid derivative. Nonsteroidal anti-inflammatory drugs (NSAIDs) are distinguished from corticosteroids as a class of anti-inflammatory agents. List of nonsteroidal steroid receptor mod ...

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 ...

that acts as a

(SERM). It consists of a

racemic mixture In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ...

of zuclomifene (~38%) and

(~62%), each of which has unique pharmacologic properties. It 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 ...

and

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). Clomifene activates 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 ...

in the setting of low baseline

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 ...

levels and partially blocks the receptor in the context of high baseline estrogen levels. Conversely, it is an

of 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 ...

. Clomifene has antiestrogenic 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 ...

. There is little clinical research on the influence of clomifene in many target tissues, such as

lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

s, the

cardiovascular system The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

, and 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. Positive effects of clomifene on

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 ...

have been observed. Clomifene has been found 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 ...

(IGF-1) levels in women. Clomifene is a long-acting ER

ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...

, with a nuclear retention of greater than 48 hours. Clomifene is a

prodrug A prodrug is a medication or compound that, after intake, is metabolized (i.e., converted within the body) into a pharmacologically active drug. Instead of administering a drug directly, a corresponding prodrug can be used to improve how the drug ...

being activated via similar

metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence of chemical reac ...

s as the related triphenylethylene SERMs tamoxifen and

toremifene Toremifene, sold under the brand name Fareston among others, is a medication which is used in the treatment of advanced breast cancer in postmenopausal women.https://www.accessdata.fda.gov/drugsatfda_docs/label/2011/020497s006lbl.pdf It is taken ...

. 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 clomifene for the ER relative to

ranges from 0.1 to 12% in different studies, which is similar to the range for tamoxifen (0.06–16%). 4-Hydroxyclomifene, a major active metabolite of clomifene, and

afimoxifene Afimoxifene, also known as 4-hydroxytamoxifen (4-OHT) and by its tentative brand name TamoGel, is a selective estrogen receptor modulator (SERM) of the triphenylethylene group and an active metabolite of tamoxifen. The drug is under development u ...

(4-hydroxytamoxifen), a major active metabolite of tamoxifen, show 89–251% and 41–246% of the affinity of estradiol for the ER in human

MCF-7 MCF-7 is a breast cancer cell line isolated in 1970 from a 69-year-old White woman. MCF-7 is the acronym of Michigan Cancer Foundation-7, referring to the institute in Detroit where the cell line was established in 1973 by Herbert Soule and co-wor ...

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a re ...

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...

s, respectively. The ER affinities of the

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...

s of 4-hydroxyclomifene were 285% for (''E'')-4-hydroxyclomifene and 16% for (''Z'')-4-hydroxyclomifene relative to estradiol. 4-Hydroxy-''N''-desmethylclomifene has similar affinity to 4-hydroxyclomifene for the ER. In one study, the affinities of clomifene and its metabolites for the

were ~100 nM for clomifene, ~2.4 nM for 4-hydroxyclomifene, ~125 nM for ''N''-desmethylclomifene, and ~1.4 nM for 4-hydroxy-''N''-desmethylclomifene. Even though clomifene has some estrogenic effect, the

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 property is believed to be the primary source for stimulating ovulation. Clomifene appears to act mostly in the

where it depletes hypothalamic ERs and blocks the

negative feedback Negative feedback (or balancing feedback) occurs when some function (Mathematics), function of the output of a system, process, or mechanism is feedback, fed back in a manner that tends to reduce the fluctuations in the output, whether caused by ...

effect of circulating

endogenous Endogenous substances and processes are those that originate from within a living system such as an organism, tissue, or cell. In contrast, exogenous substances and processes are those that originate from outside of an organism. For example, es ...

, which in turn results in an increase in

hypothalamic The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus i ...

gonadotropin-releasing hormone Gonadotropin-releasing hormone (GnRH) is a releasing hormone responsible for the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. GnRH is a tropic peptide hormone synthesized and release ...

(GnRH) pulse frequency and circulating concentrations of

follicle-stimulating hormone Follicle-stimulating hormone (FSH) is a gonadotropin, a glycoprotein polypeptide hormone. FSH is synthesized and secreted by the gonadotropic cells of the anterior pituitary gland and regulates the development, growth, pubertal maturation, an ...

(FSH) and

luteinizing hormone Luteinizing hormone (LH, also known as luteinising hormone, lutropin and sometimes lutrophin) is a hormone produced by gonadotropic cells in the anterior pituitary gland. The production of LH is regulated by gonadotropin-releasing hormone (GnRH) ...

(LH). In normal physiologic female hormonal cycling, at 7 days past

ovulation Ovulation is the release of eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells. After ovulation, during the luteal phase, the egg will be available to be fertilized ...

, high levels of estrogen and

progesterone Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the m ...

produced from the corpus luteum inhibit GnRH, FSH, and LH at the hypothalamus and anterior pituitary. If fertilization does not occur in the post-ovulation period the corpus luteum disintegrates due to a lack of

human chorionic gonadotropin Human chorionic gonadotropin (hCG) is a hormone for the maternal recognition of pregnancy produced by trophoblast cells that are surrounding a growing embryo (syncytiotrophoblast initially), which eventually forms the placenta after implantation ...

(hCG). This would normally be produced by the embryo in the effort of maintaining progesterone and estrogen levels during pregnancy. Therapeutically, clomifene is given early in the

menstrual cycle The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that make pregnancy possible. The ovarian cycle controls the production and release of eggs a ...

. It is typically prescribed beginning on day 3 and continuing for five days. By that time, FSH levels are rising steadily, causing the development of a few follicles. Follicles, in turn, produce the estrogen, which circulates in serum. In the presence of clomifene, the body perceives a low level of estrogen, similar to day 22 in the previous cycle. Since estrogen can no longer effectively exert negative feedback on the hypothalamus, GnRH secretion becomes more rapidly pulsatile, which results in increased pituitary gonadotropin release. (More rapid, lower amplitude pulses of GnRH lead to increased LH and FSH secretion, while more irregular, larger amplitude pulses of GnRH leads to a decrease in the ratio of LH to FSH.) Increased FSH levels cause the growth of more ovarian follicles, and subsequently rupture of follicles resulting in ovulation. Ovulation occurs most often 6 to 7 days after a course of clomifene. In normal men, 50 mg/day clomifene for 8 months has been found to increase

testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...

levels by around 870 ng/dL in younger men and by around 490 ng/dL in elderly men.

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 ...

levels increased by 62 pg/mL in younger men and by 40 pg/mL in elderly men. These findings suggest that the progonadotropic effects of clomifene are stronger in younger men than in older men. In men with

, clomifene has been found to increase testosterone levels by 293 to 362 ng/dL and estradiol levels by 5.5 to 13 pg/mL. In a large clinical study of men with low testosterone levels (<400 ng/dL), 25 mg/day clomifene increased testosterone levels from 309 ng/dL to 642 ng/dL after 3 months of therapy. No significant changes in

HDL cholesterol High-density lipoprotein (HDL) is one of the five major groups of lipoproteins. Lipoproteins are complex particles composed of multiple proteins which transport all fat molecules (lipids) around the body within the water outside cells. They are t ...

triglyceride A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride''). Triglycerides are the main constituents of body fat in humans and other vertebrates, as w ...

s, fasting

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...

, or

prolactin Prolactin (PRL), also known as lactotropin, is a protein best known for its role in enabling mammals to produce milk. It is influential in over 300 separate processes in various vertebrates, including humans. Prolactin is secreted from the pit ...

levels were observed, although

total 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 membrane ...

levels decreased significantly.

Other activities

Clomifene is an inhibitor of the conversion of

desmosterol Desmosterol is a molecule similar to cholesterol. Desmosterol is the immediate precursor of cholesterol in the Bloch pathway of cholesterol biosynthesis. 24-dehydrocholesterol reductase catalyses the reduction of desmosterol to cholesterol. It i ...

into

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 ...

by the

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 ...

24-dehydrocholesterol reductase. Concerns about possible induction of

desmosterolosis Desmosterolosis in medicine and biology is a defect in cholesterol biosynthesis. It results in an accumulation of desmosterol and a variety of associated symptoms. Only two cases have been reported as of 2007. The condition is due to inactivating ...

and associated symptoms such as

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 and

ichthyosis Ichthyosis is a family of genetic skin disorders characterized by dry, thickened, scaly skin. The more than 20 types of ichthyosis range in severity of symptoms, outward appearance, underlying genetic cause and mode of inheritance (e.g., dominan ...

with extended exposure precluded the use of clomifene in the treatment of breast cancer. Continuous use of clomifene has been found to increase desmosterol levels by 10% and continuous high doses of clomifene (200 mg/day) have been reported to produce visual disturbances.

Pharmacokinetics

Clomifene produces ''N''-desmethylclomifene,

clomifenoxide Clomifenoxide (INN), also known as clomifene ''N''-oxide, is a nonsteroidal selective estrogen receptor modulator (SERM) of the triphenylethylene group that is described as an antiestrogen and " gonad stimulant" and was never marketed. It is an ...

(clomifene ''N''-oxide), 4-hydroxyclomifene, and 4-hydroxy-''N''-desmethylclomifene as

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. Clomifene is a

most importantly of 4-hydroxyclomifene and 4-hydroxy-''N''-desmethylclomifene, which are the most active of its metabolites. In one study, the peak levels after a single 50 mg dose of clomifene were 20.37 nmol/L for clomifene, 0.95 nmol/L for 4-hydroxyclomifene, and 1.15 nmol/L for 4-hydroxy-''N''-desmethylclomifene. Clomifene has an

onset of action Onset of action is the duration of time it takes for a drug's effects to come to prominence upon administration. With oral administration, it typically ranges anywhere from 20 minutes to over an hour, depending on the drug in question. Other meth ...

of 5 to 10 days following course of treatment and an

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 ...

about 5 days. In one study, after a single 50 mg dose of clomifene, the half-life of clomifene was 128 hours (5.3 days), of 4-hydroxyclomifene was 13 hours, and of 4-hydroxy-''N''-desmethylclomifene was 15 hours. Individuals with the CYP2D6*10

allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...

showed longer half-lives for 4-hydroxyclomifene and 4-hydroxy-''N''-desmethylclomifene. Most clomifene metabolism occurs 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 ...

, where it undergoes

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 ...

. Clomifene and its metabolites are

excreted Excretion is a process in which metabolic waste is eliminated from an organism. In vertebrates this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific tasks after lea ...

primarily through

feces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...

(42%), and excretion can occur up to 6 weeks after discontinuation.

Chemistry

Clomifene is a

derivative. It is a mixture of two

geometric isomers Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is ca ...

(''(E)''-clomifene) and zuclomifene (''(Z)''-clomifene). These two isomers have been found to contribute to the mixed estrogenic and antiestrogenic properties of clomifene.

History

A team at William S. Merrell Chemical Company led by Frank Palopoli synthesized clomifene in 1956; after its biological activity was confirmed a patent was filed and issued in November 1959. Scientists at Merrell had previously synthesized

chlorotrianisene Chlorotrianisene (CTA), also known as tri-''p''-anisylchloroethylene (TACE) and sold under the brand name Tace among others, is a nonsteroidal estrogen related to diethylstilbestrol (DES) which was previously used in the treatment of menopausal ...

and

ethamoxytriphetol Ethamoxytriphetol (developmental code name MER-25) is a synthetic nonsteroidal antiestrogen that was studied clinically in the late 1950s and early 1960s but was never marketed. MER-25 was first reported in 1958, and was the first antiestrogen t ...

. Clomifene was studied 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 ...

during the period of 1964 to 1974 and was found to be effective but was abandoned due to concerns about

with extended use. Short-term use (e.g. days to months) did not raise the same concerns and clomifene continued to be studied for other indications. Clinical studies were conducted under an Investigational New Drug Application; clomifene was third drug for which an IND had been filed under the 1962

Kefauver Harris Amendment Carey Estes Kefauver (; July 26, 1903 – August 10, 1963) was an American politician from Tennessee. A member of the Democratic Party, he served in the U.S. House of Representatives from 1939 to 1949 and in the Senate from 1949 until his d ...

to the

Federal Food, Drug, and Cosmetic Act The United States Federal Food, Drug, and Cosmetic Act (abbreviated as FFDCA, FDCA, or FD&C) is a set of laws passed by the United States Congress in 1938 giving authority to the U.S. Food and Drug Administration (FDA) to oversee the safety of f ...

that had been passed in response to the

thalidomide Thalidomide, sold under the brand names Contergan and Thalomid among others, is a medication used to treat a number of cancers (including multiple myeloma), graft-versus-host disease, and a number of skin conditions including complications of ...

tragedy. It was approved for marketing in 1967 under the brand name Clomid. It was first used to treat cases of

oligomenorrhea Oligomenorrhea is infrequent (or, in occasional usage, very light) menstruation. More strictly, it is menstrual periods occurring at intervals of greater than 35 days, with only four to nine periods in a year.thefreedictionary.com > oligomenorrhea ...

but was expanded to include treatment of

when women undergoing treatment had higher than expected rates of pregnancy. The drug is widely considered to have been a revolution in the treatment of female infertility, the beginning of the modern era of assisted reproductive technology, and the beginning of what in the words of

Eli Y. Adashi Eli Y. Adashi is an American physician-scientist-executive who served as the Fifth Dean of Medicine and Biological Sciences at Brown University. Adashi is presently a tenured Professor of Medical Science with the Warren Alpert Medical School of ...

, was "the onset of the US multiple births epidemic". The company was acquired by Dow Chemical in 1980, and in 1989 Dow Chemical acquired 67 percent interest of Marion Laboratories, which was renamed Marion Merrell Dow. In 1995 Hoechst AG acquired the pharmaceutical business of Marion Merrell Dow. Hoechst in turn became part of

Aventis Sanofi S.A. is a French multinational pharmaceutical and healthcare company headquartered in Paris, France. Originally, the corporation was established in 1973 and merged with Synthélabo in 1999 to form Sanofi-Synthélabo. In 2004, Sanofi-Sy ...

in 1999,Arturo Bris and Christos Cabolis,
Corporate Governance Convergence Through Cross-Border Mergers The Case of Aventis
, Chapter 4 i

Eds Greg N. Gregoriou, Luc Renneboog. Academic Press, 26 July 2007 and subsequently a part of

Sanofi Sanofi S.A. is a French multinational pharmaceutical and healthcare company headquartered in Paris, France. Originally, the corporation was established in 1973 and merged with Synthélabo in 1999 to form Sanofi-Synthélabo. In 2004, Sanofi-Syn ...

. It became the most widely prescribed drug for

to reverse

Society and culture

Brand names

Clomifene is marketed under many brand names worldwide, including Beclom, Bemot, Biogen, Blesifen, Chloramiphene, Clofert, Clomene, ClomHEXAL, Clomi, Clomid, Clomidac, Clomifen, Clomifencitrat, Clomifene, Clomifène, Clomifene citrate, Clomifeni citras, Clomifeno, Clomifert, Clomihexal, Clomiphen, Clomiphene, Clomiphene Citrate, Cloninn, Clostil, Clostilbegyt, Clovertil, Clovul, Dipthen, Dufine, Duinum, Fensipros, Fertab, Fertec, Fertex, Ferticlo, Fertil, Fertilan, Fertilphen, Fertin, Fertomid, Ferton, Fertotab, Fertyl, Fetrop, Folistim, Genoclom, Genozym, Hete, I-Clom, Ikaclomin, Klofit, Klomen, Klomifen, Lomifen, MER 41, Milophene, Ofertil, Omifin, Ova-mit, Ovamit, Ovinum, Ovipreg, Ovofar, Ovuclon, Ovulet, Pergotime, Pinfetil, Profertil, Prolifen, Provula, Reomen, Serofene, Serophene, Serpafar, Serpafar, Surole, Tocofeno, and Zimaquin.

Regulation

Clomifene is included on the

list of illegal doping agents in sport. It is listed because it is an "anti-estrogenic substance".

Research

Clomifene has been used almost exclusively for ovulation induction in

premenopausal 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, and has been studied very limitedly 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. Clomifene was studied for treatment and prevention of

, but issues with toxicity led to abandonment of this indication, as did the discovery of

. Like the structurally related drug

triparanol Triparanol (, ; brand name and development code MER/29, as well as many other brand names) was the first synthetic cholesterol-lowering drug. It was patented in 1959 and introduced in the United States in 1960. The developmental code name of tripa ...

, clomifene is known to

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 ...

the

24-dehydrocholesterol reductase and increase circulating

levels, making it unfavorable for extended use in breast cancer due to risk of side effects like irreversible

cataracts 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 ...

References

External links

* {{Portal bar, Medicine 2-Phenoxyethanamines 24-Dehydrocholesterol reductase inhibitors Diethylamino compounds Hepatotoxins Merck brands Organochlorides Prodrugs Progonadotropins Selective estrogen receptor modulators Triphenylethylenes World Health Organization essential medicines World Anti-Doping Agency prohibited substances Wikipedia medicine articles ready to translate