Some research was done regarding this in Germany with DNA vaccines. They came to the conclusion that delivering these vaccines via a tattoo needle was 16 times more effective than doing it the natural way of injecting it into a vein or muscle. The reason this method works is because the vibrating of the tattoo needle automatically starts preparing the body's immune system, which then increases the body's response to the drug. Experts are saying that this method of cheating is a little bizarre but they don't put it past some athlete's to actually try it.
If you ask me I think this idea is pretty brilliant, but there is one flaw to this cheating plan. It would be very easy to see if some athlete's are doing this. I mean it will be pretty obvious that they just got a "tattoo" because the skin would be red and irritated. Not unless the drugs that they are using stay effective hours after inserting them. Nonetheless this method of inserting performance-enhancers is pretty interesting.