Clomid vs. Enclomiphene: What is the Difference?

By Josh Whalen
December 21, 2023

Clomiphene citrate, commonly known as Clomid, is a medication frequently used in the treatment of infertility. It is well-known for its ability to stimulate ovulation in women, thereby increasing the chances of pregnancy. Clomid contains two isomers, enclomiphene and zuclomiphene, which have distinct properties and effects. In recent years, a purified form of enclomiphene has been developed as a potential alternative to Clomid, sparking interest in comparing these two medications. In this article, we will explore the differences between Clomid Vs enclomiphene, their mechanisms of action, and potential side effects.

Clomid: A Brief Overview

Clomiphene citrate, marketed under the brand name Clomid, has been used for several decades to treat infertility, particularly in women with anovulation or irregular menstrual cycles. Clomid's mechanism of action involves modulating the body's hormonal balance to induce ovulation. It achieves this by acting on the hypothalamus and pituitary gland, thereby increasing the production of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These hormones play crucial roles in regulating the menstrual cycle and promoting the development and release of mature eggs from the ovaries.

The Two Isomers of Clomid

Clomid, as mentioned earlier, consists of two isomers: enclomiphene and zuclomiphene. These isomers have distinct chemical structures, and they contribute differently to the medication's overall effects.

  • Enclomiphene:
    • Enclomiphene is the "active" isomer of Clomid, primarily responsible for its ovulation-inducing effects.
    • It selectively binds to estrogen receptors in the hypothalamus, blocking the negative feedback signals sent to the pituitary gland.
    • By disrupting this feedback loop, enclomiphene increases the release of FSH and LH, ultimately stimulating ovulation.
  • Zuclomiphene:
    • Zuclomiphene, on the other hand, is the "inactive" isomer of Clomid.
    • It also binds to estrogen receptors but with a weaker affinity compared to enclomiphene.
    • Zuclomiphene has a longer half-life in the body, which can lead to an accumulation of estrogen receptor binding over time.

Enclomiphene: A Newer Alternative

Enclomiphene, in its purified form, has emerged as a potential alternative to Clomid for the treatment of infertility. Researchers have been interested in enclomiphene due to its more selective action on estrogen receptors, which may lead to fewer side effects compared to Clomid. Enclomiphene is available under the brand name Androxal.

Differences Between Clomid and Enclomiphene

  • Selectivity:
    • Clomid contains both enclomiphene and zuclomiphene, while enclomiphene is the active ingredient in its purified form.
    • Enclomiphene is more selective in binding to estrogen receptors, reducing the risk of estrogenic side effects.
  • Estrogenic Side Effects:
    • Clomid's use can lead to estrogenic side effects, such as hot flashes, mood swings, and breast tenderness, due to the combined action of its isomers.
    • Enclomiphene, being more selective, may result in fewer estrogenic side effects.
  • Accumulation:
    • Zuclomiphene, present in Clomid, has a longer half-life in the body, potentially leading to an accumulation of estrogen receptor binding over time.
    • Enclomiphene, as a single isomer, does not have this issue.
  • Dosing:
    • Clomid is typically administered in a 50:50 ratio of enclomiphene and zuclomiphene.
    • Enclomiphene, in its purified form (Androxal), provides a more precise and consistent dose of the active isomer.

Mechanisms of Action

While both Clomid and enclomiphene are used to induce ovulation, they differ in their mechanisms of action:

  • Clomid works by disrupting the negative feedback loop between estrogen and the hypothalamus, leading to increased FSH and LH production.
  • Enclomiphene, being more selective, achieves the same effect with fewer estrogenic side effects, making it a potentially more attractive option for some patients.

Side Effects

Side effects are a crucial consideration when comparing Clomid and enclomiphene. It is essential to consult with a healthcare provider before starting any medication, as individual responses may vary. Some potential side effects of Clomid and enclomiphene include:

  • Estrogenic Effects:
    • Hot flashes
    • Mood swings
    • Breast tenderness
    • Vaginal dryness
  • Ovarian Hyperstimulation Syndrome (OHSS):
    • Rare but can occur with both medications, leading to abdominal pain and bloating.
  • Vision Changes:
    • Blurred vision or visual disturbances have been reported, particularly with Clomid. Patients should seek immediate medical attention if these occur.
  • Multiple Pregnancies:
    • Both medications can increase the risk of multiple pregnancies, such as twins or triplets.
  • Ovarian Cysts:
    • Enlargement of the ovaries or the development of ovarian cysts can occur.
  • Gastrointestinal Symptoms:
    • Nausea and abdominal discomfort are possible side effects.
  • Headaches:
    • Some individuals may experience headaches while taking these medications.

It's important to note that individual experiences with side effects can vary widely. Healthcare providers will monitor patients closely during treatment to minimize risks and adjust the dosage if necessary.

Informed decision

Clomid and enclomiphene are both effective medications for inducing ovulation and treating infertility. However, they differ in their composition, selectivity, and potential side effects. Enclomiphene, in its purified form, may offer a more precise and potentially better-tolerated option for some patients due to its selective action on estrogen receptors and reduced risk of estrogenic side effects.

Ultimately, the choice between Clomid and enclomiphene should be made in consultation with a healthcare provider, taking into account individual medical history, preferences, and treatment goals. The goal is to maximize the chances of achieving a healthy pregnancy while minimizing the risk of side effects and complications associated with these medications.

For more detailed information on the side effects and specific dosing guidelines for Clomid and enclomiphene, it is advisable to refer to reputable medical resources and consult with a healthcare professional.

Back to Blog
More Thoughts
See all Articles
Schedule Online Consult