On November 23, 2010, Lilly announced it has received FDA approval on a new topical testosterone medication. The product is called Axiron (pronounced AXE-e-RON). It is the first topical testosterone product approved for application via the armpit (axilla). At first glance, Axiron appears to be quite similar to the topical testosterone gels Androgel and Testim. An up close look, however, finds there are also some substantial differences beyond where it is applied. Some of these differences may amount to advantages, others perhaps disadvantages. Before you run out and change over to this new medication, we should take a few minutes to review. Is Axiron the testosterone for you? Let’s try to find out.
Axiron is similar in appearance to Androgel Pump. Instead of dispensing the topical solution into your hand, however, it comes with an applicator cup that resembles a roll-on antiperspirant. The topical solution is rubbed into the armpit area using this applicator. Note that the product has no deodorant or antiperspirant properties, though can be used with such products. To make use of the smaller surface area of the axillae, the solution contains 2% testosterone instead of the 1% found in Androgel and Testim. Axiron is given at a dosage of 30-120 mg per day, of which only a small percentage reaches the blood. The pattern of release is similar to that of Androgel or Testim, with a slight peak the first few hours, and somewhat steady maintenance of testosterone for the rest of the 24-hour period.
Let’s examine the potential advantages to Axiron next to its predecessors Androgel and Testim. For one, the higher concentration and smaller skin surface area means that there is less total solution to apply to your body each day. Anyone that has used Androgel or Testim knows that it is quite a lot of gel to rub on your arms and stomach every day (especially at a 10 g dosage). The applicator for Axiron is also “no touch,” so there is no hormone to wash off your hands. It is a much cleaner process. With the testosterone solution coming into direct contact with less exposed areas of the body, there should also be less risk of transference to others (of course this is still always a concern with a topical testosterone).
While there are many seemingly positive attributes to Axiron that might make it a strong contender on the U.S. hormone market, this new preparation may also have some notable disadvantages. In particular, the more limited surface area of the axillae may cause the solution to hit saturation limits very quickly. The skin will only absorb a certain amount of hormone; you cannot keep escalating the dosage of a topical product without running into diminishing absorption at some point. In the case of Axiron, the product is applied to a very small area of skin. This seems to cause absorption limits to be reached at much lower thresholds compared to Androgel/Testim.
The problem with delivery limits seems to be apparent in the prescribing information. The product delivers 30 mg per pump; so 1-4 pumps are used per day. The data shows an average testosterone concentration of 300-350 ng/dL after 7 days of using 1 pump per day. With two pumps, the level hovers somewhere between 350-450 ng/dL. When the individual needs 3-4 pumps, the armpit(s) must be used twice. The resulting testosterone level at 3 pumps is only marginally higher than 2 (400-475 ng/nL). The 7-day values for 4 pumps are not provided, however, data is given that shows the average testosterone concentration after 120 days of use to be 493, 506, 415, and 390 ng/dL for the 30, 60, 90, and 120 mg doses, respectively. The double applications on the armpit(s) are not yielding higher levels.
The literature adopts the range of 300-1050 ng/dL as “normal” (many researchers, myself included, extend the normal range to 1200 ng/dL). Even with this scale, Axiron produces an average testosterone level that failed to reach the mid-point of 675 ng/dL. Regardless of the dose applied, the average testosterone level remained within the lower half of the normal range (around 400-500 ng/dL). In comparison, a 100 mg dose of Androgel results in average levels of around 800 ng/dL. This may be a very important distinction. We know from other studies that higher blood levels of testosterone are often necessary to correct certain symptoms of androgen deficiency. The highest quartile of normal is also a common objective of HRT/anti-aging medicine. Many patients will likely be unable to achieve this with the recommended use of Axiron.
Axiron appears to have both strong positives and negatives. For patients that are asymptomatic on low doses of other topical testosterone medications (for example, 50 mg/5 g per day of Androgel or Testim), this product may be an easier and “less messy” alternative. For those that require higher blood levels of testosterone, however, Axiron may not be a sufficient product. With average blood levels falling in the lower half or quartile of normal, it is unlikely to become a primary item of choice with physicians that strive to “optimize” testosterone levels at the higher end of the normal range. While some patients may achieve such levels with this product, its inconsistency to do so will likely leave Androgel and Testim as the primary topical testosterone products of choice for this type of application.
Eli Lilly & Company Press Release: http://newsroom.lilly.com/releasedetail.cfm?ReleaseID=452131