Bicalutamide

Bicalutamide is a potent anti-androgen. Unlike other anti-androgens, it does not suppress the production of testosterone (and its sister enzalutamide actually increases the circulating T due to being able to cross the blood-brain barrier and stress the negative feedback loop!)

Tips and tricks
Bicalutamide can actually raise your testosterone levels, so don't be surprised to see that on your chart. That means it's working! It's getting increasingly popular and seems to work for many.

Transgender studies
Bicalutamide is used as an antiandrogen in hormone therapy for transgender women and this has been mentioned in a number of secondary sources,    Moreover, feminization and demasculinization are very well-documented side effects of bicalutamide in men treated with it for prostate cancer (50-150 mg/day) and bicalutamide has been used in the treatment of hirsutism in women in at least three studies (25-50 mg/day; dates 2002, 2016, 2017). However, until very recently there were no published studies evaluating bicalutamide in transgender women. In 2017, the first study of bicalutamide for male-to-female hormone therapy was published. Bicalutamide was used as a puberty blocker at a dosage of 50 mg/day as an alternative to GnRH analogues in 14 adolescent transgender girls of mean age 15.8 years (range 12 to 18.4 years) between 2013 and 2017. Of the girls, three received estrogen concurrently while 11 received only bicalutamide. Seven of the girls returned for follow-up by the time that the report was published. After a mean of about 5.7 months, 86% (6 of 7) of the girls showed breast development; the degree was Tanner stage III in four (57%), Tanner stage II in one (14%), and mixed Tanner stage III/II of the right and left breast in one (14%). The one patient that did not show breast development at that follow-up did show breast development at her second follow-up at 12.5 months; she had Tanner stage III breast development at that time. Liver function tests were obtained in four of the girls and were unremarkable. Estradiol levels were obtained in three of the girls and were 26 to 61 pg/mL while testosterone levels were obtained in two and were 524 to 619 ng/dL. The researchers concluded that bicalutamide is useful as an antiandrogen and puberty blocker in adolescent transgender girls and that it has a secondary benefit of promoting feminization and breast development in such subjects. They called for further studies to evaluate the potential role of bicalutamide in the therapeutic armamentarium for the treatment of transgender girls and women.

While bicalutamide has only recently been assessed in transgender females in one study, nilutamide has been assessed in transgender women in five studies/publications between 1987 and 1989. It was found to be effective as an antiandrogen and in promoting feminization in these studies both alone and in combination with ethinylestradiol. The dosage of nilutamide used in these studies was the prostate cancer monotherapy dosage of 300 mg/day, which is roughly equivalent to a bicalutamide dosage of 150 mg/day. Nilutamide itself is rarely used nowadays both for prostate cancer and for other indications due to a high risk of lung toxicity that can potentially result in death and hence is no longer recommended for use as an antiandrogen in general. Bicalutamide can be used instead of nilutamide and would be anticipated to have the same if not greater benefits due to its greater potency and efficacy as an antiandrogen (same mechanism of action – selective androgen receptor antagonist – but higher affinity for the androgen receptor and longer elimination half-life).

With spironolactone
Both bicalutamide and spironolactone have been studied in the treatment of benign prostatic hyperplasia (otherwise known as enlarged prostate) in men. This condition is androgen-dependent and so antiandrogens can treat it. Bicalutamide at a dosage of 50 mg/day decreased prostate volume by 26%. Breast tenderness was reported in 93% and gynecomastia was reported in 54% of the men. In contrast, spironolactone at a dosage of 100 mg/day failed to affect prostate volume and caused gynecomastia in only 5% of men. Another study has, however, found a rate of gynecomastia of 7% with 25 to 50 mg/day spironolactone and a rate of 52% with doses of spironolactone of 150 mg/day or higher. That said, 150 mg/day bicalutamide was found to cause gynecomastia at a rate of 69% in a large study. Taken together, these findings suggest that bicalutamide may be a considerably more efficacious antiandrogen than spironolactone.