Enclomiphene (Enclomiphene Citrate)

Enclomiphene citrate is the pharmacologically active trans-isomer of clomiphene citrate, the fertility drug sold as Clomid. Traditional Clomid contains two isomers: enclomiphene (trans) and zuclomiphene (cis). The problem with mixed-isomer Clomid is that zuclomiphene acts as a partial estrogen agonist with a very long half-life (weeks), accumulating over time and causing estrogenic side effects like mood swings, visual disturbances, and gynecomastia risk. By isolating the trans-isomer, enclomiphene delivers the testosterone-boosting benefits of Clomid without the estrogenic baggage. It's a clean estrogen receptor antagonist at the hypothalamus. The clinical data behind enclomiphene is surprisingly strong for a compound that never received FDA approval. Repros Therapeutics (now Allergan) ran multiple phase 3 trials under the brand name Androxal. The ZA-304 and ZA-305 trials enrolled over 800 men with secondary hypogonadism (low testosterone with low or normal LH/FSH). Results showed consistent testosterone normalization: men starting at 200-300 ng/dL typically reached 450-600 ng/dL within 4-6 weeks on 12.5-25 mg daily dosing. The real differentiator from TRT showed up in the fertility data. A 2015 study in Fertility and Sterility (PMID: 25597653) compared enclomiphene head-to-head against topical testosterone. Both raised testosterone levels similarly, but topical T crushed sperm counts while enclomiphene maintained them completely. For men in their 30s and 40s who want testosterone support but haven't finished having children, this is a significant advantage. The FDA rejected Androxal's New Drug Application twice, in 2015 and again in 2018. Both times, the rejection was based on manufacturing and bioequivalence concerns between production lots, not on safety or efficacy data. The clinical trial results themselves were never questioned. This unusual situation left enclomiphene in regulatory limbo: proven effective in large trials but unavailable as a branded pharmaceutical. Compounding pharmacies stepped in to fill the gap. Today, enclomiphene is widely available through 503A and 503B compounding pharmacies at $40-120/month, depending on dosage and pharmacy. Because it's a small molecule (not a peptide), it wasn't affected by the FDA's 2023 peptide restrictions or the 2026 HHS reclassification. The standard protocol starts at 12.5 mg daily, taken in the morning. Bloodwork at 6-8 weeks checks total testosterone, free testosterone, estradiol, LH, and FSH. If testosterone response is insufficient, the dose can be increased to 25 mg daily. Some clinicians prescribe 50 mg daily, though this exceeds the doses studied in phase 3 trials. One important caveat: enclomiphene works by stimulating the testes to produce more testosterone. If the testes can't respond (primary hypogonadism, shown by elevated LH/FSH), enclomiphene won't help. A baseline LH/FSH panel before starting treatment helps identify candidates who are likely to respond. Side effects are generally mild. Headaches and occasional hot flashes are the most common reports. The visual disturbances associated with traditional Clomid (zuclomiphene-mediated) are rare with isolated enclomiphene. Some men experience elevated estradiol as a downstream effect of higher testosterone aromatization, which may require monitoring.