Testosterone Is Testosterone Or Is It?

As you know, numerous drugs reach the market place yearly.  It's near impossible to stay abreast of every new development, especially as a family physician, but we try for the sake of our patients.  One way to keep up-to-date is to meet with the ubiquitous but currently out-of-vogue pharmaceutical representatives.  However, in some practices, especially academic ones, exposure to these drug reps is severely limited, if allowed at all.  Recent studies have shown that, try as we might & despite our loud protests, our prescribing pens & now our electronic keyboards are easily persuaded by free meals & trinkets, not to mention the thousands if not millions of dollars paid to fund grants & serve as a thought leader.

So what's the alternative?  Many of the drug databases point out new drugs as they reach the market.  Some even discuss possible options in Phase 3 trials.  One of these databases, Monthly Prescribing Reference, recently reported that testosterone undecanoate received orphan drug designation for constitutional delay of growth & puberty in adolescent boys (14-17yo).  This is the same testosterone undecanoate that is available outside the States as injectable Nebido, a long acting formulation requiring just a few injections a year.

It turns out that when taken orally, testosterone undecanoate is absorbed by the lymphatic system and thus avoids breakdown in the liver prior to reaching its intended sites of action.  This is a fancy way of saying it avoids all the liver issues associated w/older forms of oral testosterone.  You see, if you swallow "regular" testosterone, it'll be absorbed in the stomach & broken down in the liver.  Thus, nothing reaches the end organs, eg muscle, brain, genitals, etc.

On the other hand, if you chemically muck around with testosterone and add a methyl group here or a fluoride molecule there (sorry, I didn't really care for organic chemistry), the liver has to work harder to break down the testosterone molecule and thus it now appears in your blood stream.  But because your liver is working harder, it starts getting "irritated" which is why I never prescribe oral testosterone.

Granted, it won't be cheap, but when SOV Therapeutics' new product hits the market, it will offer a much easier option for testosterone replacement therapy in hypogonadal men, albeit off-label.

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