The tennis world was rocked earlier this week by the revelation that five-time Grand Slam champion Maria Sharapova had failed a drug test at the Australian Open. The backlash from Sharapova's announcement was both swift and fierce, with sponsors like Nike and TAG Heur taking a step back from their relationship with the lithe tennis phenom, and fans across the world wondering what will become of one of the sport's most recognizable players.

Only the drug that Sharapova was said to have taken, Meldonium, is not the normal performance enhancer for which professional athletes tend to be caught. It doesn't

According to the drug's inventor, there's a very good reason for that.

Ivars Kalvins said recently that Meldonium "is not doping." He admitted that the drug protects the cells of the heart against ischemia, a condition that stems from blood circulation issues, but took issue with the assertion that that amounted to an illegal attempt at perfromance enhancement.

"This is not the same as increase of performance," Kalvins said.

Meldonium was banned by the World Anti-Doping Agency on Jan. 1, due to "evidence of its use by athletes with the intention of enhancing performance."

The drug, which was regularly given to Soviet troops in the 1980s to boost stamina, is normally prescribed on a four to six week course. Sharapova admitted that she had been using the drug over an approximately 10-year period.

Sharapova's lawyer, John J. Haggerty, attempted to walk back his client's comments to a certain extent, saying that while Sharapova may have been using the drug, which is also known as mildronate, over that decade or so period, she was not using it on a daily or even regular basis.

Kalvins said that the drug is still used by military forces around the world because it protects soldiers from blood flow problems that can occur due to fighting in less oxygenated areas like the mountains or underwater.

Sharapova is not alone in having tested positive for the drug as several athletes in a variety of sports have been caught using meldonium already.