Drugs can be added and removed from this list by WADA annually, although not all of the banned substances are explicitly named. Caroline Hatton, PhD , a sports anti-doping science consultant, told in a Mar. 12, 2010 email that "A key concept in prohibited lists is that they avoid being finite. Instead of listing all banned drugs one by one, they list entire drug classes and name drugs merely as examples. This is to keep users who took designer drugs from claiming that they didn't break the rules because the drugs they took weren't listed."
Transdermal patches (adhesive patches placed on the skin) may also be used to deliver a steady dose through the skin and into the bloodstream. Testosterone-containing creams and gels that are applied daily to the skin are also available, but absorption is inefficient (roughly 10%, varying between individuals) and these treatments tend to be more expensive. Individuals who are especially physically active and/or bathe often may not be good candidates, since the medication can be washed off and may take up to six hours to be fully absorbed. There is also the risk that an intimate partner or child may come in contact with the application site and inadvertently dose himself or herself; children and women are highly sensitive to testosterone and can suffer unintended masculinization and health effects, even from small doses. Injection is the most common method used by individuals administering AAS for non-medical purposes.