Following up on yesterday’s post, I went looking today for information on cyproterone acetate and spironolactone, after seeing it suggested (but unverified) in Wikipedia that one (spiro) was the most commonly prescribed anti-androgen used for HRT in the United States and the other (cypro) was the most commonly prescribed internationally. Is this true? And if so, why?
For drug information in the United States, the best place to start is usually the Physician’s Desk Reference (PDR), which is pretty much the medical standard for prescription drugs in the U.S. Looking into this question quickly reveals why spiro may be more widely prescribed in the United States: as it turns out, cyproterone acetate hasn’t been approved by the FDA, and the PDR only contains FDA-approved drugs. Thus, the mystery is solved: they don’t prescribe cypro in the U.S. because they can’t. So far, I haven’t found a clear explanation why the FDA hasn’t approved the drug. It’s been around for half a century, so it’s likely been considered and rejected for some reason or other. [It’s worth noting that the FDA’s lack of approval means cypro cannot be used for any treatment in the United States, not just HRT.] But until it is, American trans women don’t have it as an option.
As for why international doctors favor one over the other? Again, the reasons are not immediately clear. Multiple studies of the two drugs as competing treatments for hirsutism found no significant benefit of one over the other in that use case; and there’s no clear study I can find in PubMed favoring one over the other for HRT (or even comparing the two as competing MtF drugs). In addition, a paper by Moore, et al (2003) that offered a comprehensive overview of endocrine treatment options for transsexuals presents the two as more or less interchangeable options for the anti-androgen component of HRT. It may simply be that, outside of the U.S., doctors have had more success with cypro. Given that spiro is also a diuretic may also be one reason why cypro is favored by patients when the choice is available. But in the U.S. spiro is the best choice. [The other more commonly prescribed anti-androgen in the U,S., finasteride, is prohibitively more expensive and is viewed, at least by doctors I’ve spoken with, as being less effective overall for HRT. ]
It’s a shame that doctors in the U.S. don’t have the option of cypro, considering how common and effective it appears to be internationally. Maybe someday, some pharmaceutical company will find reason to re-seek FDA approval. Until then, I guess American MtFs will just have to take what they can get (and stay close to a bathroom!).
This post is occasionally updated to maintain its content. Last revision 05/01/2014..]