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Transfeminine Science

Information on Bicalutamide (Casodex) as an Antiandrogen for Transfeminine People

By Aly W. | First published September 22, 2018 | Last modified September 19, 2021

Introduction

This is a collection of information on the topic of bicalutamide (brand name Casodex) as an antiandrogen and component of hormone therapy for transfeminine people. Transfeminine people often inquire about sources of information for bicalutamide for themselves and their medical providers so I thought it’d be helpful to have an index of this information.

What is Bicalutamide?

Bicalutamide is a nonsteroidal antiandrogen and works by acting as a potent and selective androgen receptor antagonist. In other words, it works by directly competing with and displacing androgens like testosterone and dihydrotestosterone from their biological target and thereby blocking their actions. This is in contrast to antiandrogens that act by decreasing testosterone levels.

Bicalutamide was developed for and is most widely used in the treatment of prostate cancer, an androgen-dependent disease. However, bicalutamide is also used for other androgen-related indications. Examples of these uses include the treatment of hirsutism and scalp hair loss in cisgender women, the treatment of gonadotropin-independent early puberty in cisgender boys, and of course hormone therapy for transfeminine people.

While bicalutamide is not yet widely used in transfeminine people, it is seeing increasing adoption in this group and has advantages over conventional antiandrogens used in transfeminine people like spironolactone and cyproterone acetate in the areas of efficacy, tolerability, and safety. However, bicalutamide itself has a small risk of liver as well as lung issues and liver function should be monitored in people taking bicalutamide particularly in the first few months of treatment.

Informational Content

Articles on This Site

Articles Specifically on Bicalutamide

General Articles Discussing Bicalutamide

Wikipedia

General Articles on Bicalutamide

Sections on Bicalutamide/Nonsteroidal Antiandrogens in Transfeminine People

Sections on Bicalutamide/Nonsteroidal Antiandrogens in Cisgender Women

Sections on Bicalutamide in Cisgender Boys with Early Puberty

Scientific Literature

Bicalutamide in Transfeminine People

Literature excerpts on bicalutamide in transfeminine people can be found here. They are listed by date of publication, from oldest to most recent. The page contains essentially everything that exists in the published literature on the topic of bicalutamide in transfeminine people. The most major piece of literature on bicalutamide in transfeminine people at this time is the following clinical study:

  • Neyman, A., Fuqua, J. S., & Eugster, E. A. (2019). Bicalutamide as an androgen blocker with secondary effect of promoting feminization in male-to-female transgender adolescents. Journal of Adolescent Health, 64(4), 544–546. [DOI:10.1016/j.jadohealth.2018.10.296]

Literature Reviews on Bicalutamide/Nonsteroidal Antiandrogens

Medicine Regulatory Materials

Medical Providers

Various clinicians are known to either be using bicalutamide or to otherwise be willing to prescribe it as an antiandrogen for transfeminine people. Below is a list of these providers.

United States

a Available for telemedicine in various areas.

b It should be noted and cautioned that Dr. Huffman and Dr. Gresham are naturopathic physicians.

c Only accepting patients ≤14 years of age.

Canada

Australia

  • Dr. Ada Cheung in Heidelberg, Victoria, Australia, near Melbourne, Australia, may be willing to prescribe bicalutamide (but unconfirmed)
  • Dr. Jon Hayes in St Leonards, New South Wales, Australia, in/near Sydney, Australia
  • Dr. Ethan Salleh at Gladstone Road Medical Centre in Highgate Hill, Queensland, Australia, near Brisbane, Australia

Know of Another?

If you know of any other clinicians who use bicalutamide or are willing to prescribe it for transfeminine people, please let me know and I will add them to this page.

Online Pharmacies

Bicalutamide is widely used in the transgender do-it-yourself (DIY) community (e.g., r/TransDIY). It can be purchased from sites such as Inhouse Pharmacy (IHP), AllDayChemist (ADC), and United Pharmacies (UP). See the r/TransDIY Wiki for a list of such pharmacies.

Coupons

GoodRx has coupons for bicalutamide in the United States and can allow for large cost savings.

Risks of Bicalutamide

Bicalutamide has almost no side effects in women (Müderris et al., 2002; Moretti et al., 2018). However, bicalutamide produces abnormal liver function tests (a predictor of liver toxicity) in a small percentage of people and is associated rarely with liver toxicity (Wiki) and lung toxicity (Wiki). Liver and lung toxicity with bicalutamide can both potentially be fatal. There has been concern and reservation about the use of bicalutamide in transfeminine people due to these risks (Aly W., 2020). It is important that transfeminine people and clinicians be aware of these risks and engage in appropriate monitoring.

Liver toxicity

In elderly men with early-stage prostate cancer, 150 mg/day bicalutamide alone was associated with elevated liver enzymes in 3.4% of users relative to 1.9% of controls—a significant 1.5% difference attributable to bicalutamide—in a very large phase 3 randomized control trial (n ≈ 8,000 total) (Wiki-Table). In elderly men with late-stage prostate cancer, 50 mg/day bicalutamide plus a gonadotropin-releasing hormone (GnRH) agonist was associated with elevated liver enzymes in 7.5% and markedly elevated liver enzymes in 0.5% in a large phase 3 randomized controlled trial (n ≈ 400 in this group) (Wiki-Table). There was no placebo group in this study; instead, the comparison group was 750 mg/day flutamide in combination with a GnRH agonist. In this flutamide comparison group, elevated liver enzymes occurred in 11.3% and markedly elevated liver enzymes occurred in 2.5% (n ≈ 400 in this group as well) (Wiki-Table). In cisgender women with scalp hair loss, 10 to 20 mg/day bicalutamide was used in almost all women and was associated with elevated liver enzymes in 3% of women in a large retrospective chart review (n ≈ 300) (Ferial Ismail et al., 2020). Also in cisgender women with scalp hair loss, 25 to 50 mg/day bicalutamide was associated with elevated liver enzymes in 11% of women in a smaller retrospective chart review (n ≈ 50) (Fernandez-Nieto et al., 2020).

Bicalutamide has been implicated in a number of published case reports of hepatotoxicity, some of which have been fatal (Wiki-Table). Causality analysis has been performed in a subset of these case reports and has implicated bicalutamide as likely responsible. The doses correspond to those widely used clinically and ranged from 50 to 150 mg/day with no clear dose dependency. The onset of hepatotoxicity ranged from 2 days to 5 months. In addition to case reports published in the medical literature, bicalutamide has been associated with around 40 cases of liver failure—of which 25 cases resulted in death—in the United States Food and Drug Administration (FDA)’s MedWatch/FAERS database. These cases have not evaluated likelihood of causality and could in a portion of instances be coincidental however. On the other hand, fewer than 10% of serious adverse reactions are reported to the FDA, and hence the true number may be much greater (Graham, Ahmad, & Piazza-Hepp, 2002). There is an unpublished report in the transgender medical community of bicalutamide causing liver failure and death in a healthy young transgender woman (Aly W., 2020).

No cases of serious liver toxicity or liver failure occurred with bicalutamide in around 8,000 men total during clinical development of bicalutamide for early or late prostate cancer (Blackledge, 1996; Kolvenbag & Blackledge, 1996; McLeod, 1997; Anderson, 2003; Iversen et al., 2004). The risk of liver toxicity with flutamide has been estimated as 0.03% (3 in every 10,000) based on data from the FDA’s MedWatch/FAERS database, although other research has had higher estimates (Wiki). Bicalutamide is considered to have significantly less liver toxicity than flutamide.

Due to the risk of liver toxicity with bicalutamide, liver monitoring should be done regularly during bicalutamide therapy. If liver enzymes are sufficiently elevated, bicalutamide should be promptly discontinued (or possibly dosage reduced). Since most cases seem to occur early into treatment (within the first 6 months), this may be the most important time for liver monitoring.

Lung toxicity

Bicalutamide has been associated with interstitial pneumonitis, which can lead to pulmonary fibrosis, and with eosinophilic lung disease (Wiki). A number of published case reports of interstitial pneumonitis and eosinophilic lung disease in association with bicalutamide exist, with some of these cases being fatal (Wiki-Table). The doses ranged from 50 to 200 mg/day and the onset ranged from 2 weeks to 6 years, but most cases occurred within the first year. A study using data from the FDA’s MedWatch/FAERS database estimated that the incidence of interstitial pneumonitis with bicalutamide was around 0.01% (1 in 10,000) (Bennett, Raisch, & Sartor, 2002). This may be an underestimate due to underreporting to the FDA and other factors however (Ahmad & Graham, 2003).