Fertodur — cyclofenil

Cyclofenil is a non-steroidal anti-estrogen that is used in the treatment of menstrual disturbances and anovualtory infertility (an inability to ovulate). It is very similar in structure to Clomid and Nolvadex, and also works in the body as a mixed estrogen agonist/antagonist. This drug is commonly used for off-label purposes by male bodybuilders and athletes, typically at the conclusion of a steroid cycle for the purpose of increasing endogenous testosterone levels. This is in an attempt to minimize the negative impact that a period of low androgen levels may have on the physique, which can include significant muscle loss. The drug HCG is also commonly used for this purpose, but it works by mimicking the action of luteinizing hormone, not as an anti-estrogen. HCG is typically looked at as a rapid acting drug, used in the first couple of weeks after the steroids are withdrawn. Anti-estrogens like cyclofenil, Clomid and/or Nolvadex are often used in conjunction with HCG, but may be continued for several weeks after the HCG has been removed (see PCT: Post Cycle Therapy). Cyclofenil stimulates the release of testosterone via its anti-estrogenic action. The hypothalamus is one target site of this. By interfering with the binding of estrogen to its receptor in this area of the body, cyclofenil blocks the negative feedback inhibition brought fourth by this sex hormone. The enhanced release of gonadotropin releasing hormone (GnRH) may result, which in turn would stimulate the pituitary to heighten the release of luteinizing hormone. LH is the primary signal for the testes to increase the production of testosterone, so its increased release (provided the testes are properly sensitive to LH) leads to an elevation in the androgen level. The anti-estrogenic effect of this drug in breast tissue has also led to its use during a steroid cycle to prevent gynecomastia, similar to how Nolvadex might be used. Cyclofenil, however, is reported to be somewhat weaker than Nolvadex, which is usually preferred as an estrogen maintenance drug. Women do occasionally find a use for anti-estrogens, most often around contest time when the management of endogenous estrogens can help increase fat loss and definition. The side effects that can be brought about by a lowering of estrogen activity in the female body are usually strong and uncomfortable, however, making this approach less than ideal.

Brand name Fertodur, Cyclofenil, Rehibin, Menopax, Neoclym, Sexovid, Ondogyne

Cyclofenil History

Cyclofenil was developed during the early 1960s, a time when other agents of the same class (such as tamoxifen and clomiphene) were being thoroughly investigated. Cyclofenil was soon released as a prescription drug agent, sold mainly to increase the chance of conception and to counter certain menopausal symptoms. Although the drug seemed to offer a good clinical effect without significant health concerns, it did not see extensive success on the global market. Instead, Nolvadex and Clomid dominated this drug category for many decades. Still, cyclofenil did not completely disappear, and remained available in certain nations. The most popular brand was Fertodur, produced by Schering. It was sold in a few countries, including Brazil, Germany, Italy, Mexico, Switzerland, and Turkey. Other popular brands have included Rehibin (U.K.), Menopax (Brazil), Neoclym (Italy), Sexovid (Japan), and Ondogyne (France). Today, although most original cyclofenil products have been discontinued, the drug can still be found in some areas including Turkey, Italy, and Brazil.

How is Cyclofenil Supplied

Cyclofenil is most commonly supplied in tablets of 200 mg.

Structural Characteristics of Cyclofenil

Cyclofenil is classified as a selective estrogen receptor modulator, with both agonist and antagonist properties. It has the chemical designation 4,4’(Cyclohexylidenemethylene)bis(phenyl acetate).

Cyclofenil Side Effects

Cyclofenil appears to be well tolerated, with a low incidence of significant side effects. Common adverse reactions include liver enzyme elevations, vasomotor flushes (hot flashes), abdominal discomfort, nausea/vomiting, breast discomfort, headache, and abnormal uterine bleeding. Premenopausal women may be more susceptible to hot flashes due to the stronger effect estrogenic disruption can have on this population. In males, the testosterone boosting properties of cyclofenil may result in some androgenic side effects including oily skin, acne, and increased libido.

Cyclofenil Administration

Cyclofenil is most commonly used (medically) to treat anovulatory infertility. Therapeutic protocols recommend a dose of 200 mg three times per day for 5 days, which is initiated near the start of the menstrual cycle. If pregnancy is not achieved with the first cycle, it may be used for 3 or 4 cycles in total. In some instances the drug is also given in lower doses to treat menopausal symptoms. When used after steroid administration (off-label) to increase natural testosterone production, a dosage 400-600 mg per day is the most common. It is often used for a period of 4 to 5 weeks as part of a comprehensive post-cycle recovery program in place of Clomid (see PCT: Post Cycle Therapy). Similar doses are used for estrogen maintenance purposes while on-cycle, although Nolvadex is usually given preference for this purpose. Some athletes have experimented with using cyclofenil as a standalone anabolic, finding its ability to increase testosterone levels beneficial. The dosage used for this purpose is typically 400-600 mg per day for 6-8 weeks. While some have reported this approach to be effective, many others find the drug too mild, especially in light of the effects of exogenous testosterone.

Cyclofenil Availability

Cyclofenil is not widely produced. Availability is presently low on the international market. When located in the U.S., the drug is usually found in the form of Fertodur, made by Schering in Turkey. Counterfeits of cyclofenil drugs have not been a significant problem.

Bodybuilders reference

Cyclofenil administration is quite similar to using HCG and CLOMID together. It is an anti-estrogen and a gonadotropin/testosterone stimulator. It does so by occupying estrogen receptors (antagonist) with a much weaker estrogenic compound and by shutting down the negative feed-back within the hypothalamus-pituitary-testes-axis (HPTA). The male body actually can produce much more testosterone than it does. Simply said, it sees no reason to do so. When the hypothalamus senses adequate testosterone/estrogen levels, either naturally (endogenous) or unnaturally (exogenous) provided, it shuts off gonadotropin release from the pituitary/hypothalamus. Thus, leydig cells in the testes do not receive the signal to produce more testosterone. Cyclofenil interferes with this negative feed-back/shut down production signal. This means that the hypothalamus - pituitary-testes-axis runs wide open to some extent, and more testosterone is produced. After about 5-6 weeks the hypothalamus figures this out and really shuts down the goodies production.

Though some strength and mass resulted with Cyclofenil use, it was not noted as a great growth drug. Some "natural" (okay) bodybuilders have used it with some results as have older individuals. However, the chemically assisted lads have used it to kick start natural testosterone production and even as a "during cycle anti-estrogen" very successfully. Normally 200 mg was taken 2-3 times daily for 4-6 weeks, either starting the last 3 weeks prior to the end of an AAS cycle or directly following a cycle. The prior method being reported as more effective since about a week is necessary for Cyclofenil to become effective and provide results. Side effects commonly reported have been; light acne, elevated sex-drive (that is a side effect?), and hot flashes.

*A note of interest; I have known several so-called natural bodybuilders who have utilized cyclofenil with a prohormone protocols in the United States with surprising results. This was effective for many reasons. Lower estrogen activity means a harder appearance. Testosterone both endogenous and exogenous combine resulted in significant total testosterone levels as well as a higher free testosterone level due to prohormones ability to uncouple testosterone from SHGB to some extent. The usual cycle consisted of 6 weeks of prohormones with 4 weeks of cyclofenil beginning week #5 of the prohormone cycle. Doing so extended the cycle 2 weeks and assured no post-cycle HPTA suppression to deal with for most athletes. Some athletes reported week #6-8 produced good secondary growth. This may have been due to an up- regulation of LH, FSH, and the conversion enzymes responsible for prohormones becoming testosterone in blood as well as decreased activity of estrogen. My concern would be the rush of estrogen post-cycle since cyclofenil only blocks estrogen receptors instead of suppressing estrogen production. In that example, for me personally, Arimidex would have been a wiser choice beginning week #5 also.

Anabolic Steroid Guide reference

Cyclofenil is not an anabolic/androgenic steroid. Cyclofenil works as an antiestrogen and, at the same time, increases the body's own testosterone production. Since Cyclofenil itself is only a very weak and mild estrogen it occupies, the estrogen receptors, and prevents the stronger estrogens from bonding with the receptors thereby becoming active. As a matter of fact, this works so well that some athletes take Cyclofenil during the steroid treatment in order to maintain a low estrogen level. The result is a lower water retention produced by the steroids and less gynecomastia. The athlete has a harder appearance, making this is a compound that can potentially be taken during the preparation for a competition. Bodybuilders, however, use it less frequently since they prefer the more readily available Nolvadex and Proviron compounds.

Based on our experience, the dosage lies be-tween 400 and 600 mg/day. Lower dosages usually do not show satisfying results. Cyclofenil, for this purpose, is either used during steroid treatment, after the treatment, before competitions with doping tests, or by "natural bodybuilders". Like HCG and Clomid, Cyclofenil is ineffective in women since it has a positive influence on the male hormone system. Even in men, the increased testosterone level attributed to the effect of Cyclofenil is not high enough to speak of drastic improvements; however, strength gains, a slight gain in body weight, a noticeable increase in energy, and a higher regeneration are possible. These results are noticeable particularly in advanced athletes who have little or no experience with steroids. Cyclofenil needs a response time of approximately one week before it becomes effective. In a few cases athletes experience a light acne, increased sexual desire, and hot flashes. The first two secondary symptoms are especially indicative that the compound is actually effective.

After discontinuance some athletes report a depressed mood and a slight decrease in physical strength. Those who take Cyclofenil as an antiestrogen during steroid treatment could experience a rebound effect when the compound is discontinued.

In the meantime, it is very difficult to find Cyclofenil and it is rarely found on the black market. The Mexican Fertodur by Schering contains 16 tablets of 200 mg each which are welded into aluminum foil with the name "Fertodur Tabletas" printed on top. Such a package costs $25-30 on the black

Newbies Research Guide reference

Cyclofenil is another non-steroidal ancillary drug used by athletes, similar to HCG and Clomid in action. This drug is most commonly used to increase endogenous testosterone levels after a cycle in an attempt to avoid a hard crash while waiting for your hormone levels to naturally balance. Similar to HCG and Clomid, cyclofenil seems to quickly and effectively raise natural levels. Anecdotally however, cyclofenil does has the reputation of being the weakest of the three. Like Clomid, cyclofenil may also act as an anti-estrogen, binding to estrogen receptor sites and blocking out other estrogens. This is especially helpful when natural testosterone levels are suppressed and an excess of estrogen may be present upon steroid termination. It should also be noted that some athletes have experimented with using cyclofenil not as a post-cycle ancillary drug, but alone and solely for it’s anabolic properties. However, anyone familiar with ana- bolics would likely be disappointed with the results cyclofenil would bring, as it is not an extremely strong product, and certainly would not work as well as anabolics. Here in the U.S., Fertodur from Mexico is probably the most commonly imported cyclofenil product although it is produced in many other countries. Currently, fakes should not be a problem with this product.


Wlliam Llewellyn (2011) - Anabolics
L. Rea (2002) - Chemical Muscle Enhancement Bodybuilders Desk Reference
Anabolic Steroid Guide
Newbies Research Guide

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