Meldonium is the banned performance-enhancing subject on everyone's lips, and in many athletes' bloodstreams. With Maria Sharapova, one of the highest paid female athletes in the world, facing a ban after she tested positive for the substance in January, saying she was taking it for legitimate medical benefits, it has become the biggest issue in sport. And with 2.2% of athletes' random urine samples testing positive for it last year, heads seem set to keep rolling.

What is meldonium?

Meldonium, which is also known by its brand name Mildronate, is a drug used to treat ischemia, a condition which reduces blood supply to parts of the body – often the heart, but also the brain, bowels and limbs. The drug's developer, Latvian drug company Grindeks, says that courses of the medication generally last 4-6 weeks.

It is also claimed to have benefits for diabetes sufferers, but there is little clinical evidence of this. This research was carried out in Russia and Poland, because the drug is only licensed for use Russia, Poland and the Baltic States.

The drug seems to have been invented to boost Soviet soldiers' endurance during the nine-year long Soviet-Afghanistan war, that began in 1979. Ivars Kalvins, 69, who invented the drug, told Latvian media that a lot of soldiers were given the drug, without being aware of it.

"High altitudes. Oxygen deprivation. If they have to run 20km with all the gear, at the end they would get ischemia," Kalvins was quoted as saying in 2009.

Why would athletes use it?

Any drug which can be used to increase physical performance in soldiers will help athletes add a few percentage points to their peak performance. Meldonium increases oxygen flow to muscles meaning an increase in stamina and endurance, and faster recovery times after intense exertion. So this drug could give athletes a slight edge over competitors, especially in competitions where endurance is a key factor of performance, such as tennis.

Is meldonium safe?

According to the drug's documentation and most reports, there are no major side effects to using meldonium. OlainFarm, a Latvian manufacturer, told the BBC that some people using the drug could suffer "headaches" and "agitation", and skin irritation is possible, but rare.

In an email to Wired magazine, a spokeswoman for Grindeks said Mildronate – the company's brand name for meldonium – is of no use for doping.

"There have been no clinical studies providing scientific evidence that acute or chronic use of meldonium increases the athlete's physical ability," she said. "Any suggestions to include meldonium in the prohibited list have no scientific basis and are not justified."

Why has it been banned?

The World Anti-Doping Authority (Wada) spent most of 2015 monitoring the drug after it became aware of its capabilities. Wada decided it had seen enough in September and declared the drug "performance-enhancing", adding it to the banned list from 1 January 2016.

Wada considers three broad contexts for any drug ban:

  1. Whether a substance improves performance,
  2. Whether it is harmful to users' health, and
  3. Whether it goes against the so-called "spirit of sport".

A drug must fail two of these tests to be banned – in this case, presumably the first and third.

After Sharapova announced she had failed the drugs test Kalvins told the news website, claimed Wada banned the drug because of the deterioration of political relationships between the East and the West, and to allow other pharmaceutical companies' rival products get a foothold in the market.

Will we see more cases?

Wada has confirmed 99 positive tests for meldonium since start of 2016, announcing 16 names including 11 Russian athletes and two Ukrainians.

The Wada laboratory in Cologne in Germany tested 8,320 random urine samples taken from sportspeople and found meldonium in 182 of them, or 2.2%. As all other banned substances combined are found in about 2% of tested samples, meldonium's is seeing massive use. It seems reasonable to assume that more athletes will be found to have been using it.

Many of the positive samples had higher amounts of meldonium in them than testers would expect if athletes had been using the drug simply medicinily. A regular six-week course would only leave trace amounts of the medication behind, suggesting that some athletes might be using the drug systematically.

Liene Kozlovska, the head of Latvia's State Sports Medicine Centre anti-doping department has suggested that athletes from Russia may not have been warned that meldonium had been banned, as RUSADA – Russia's anti-doping agency – was suspended in late 2015, after a special Wada investigation found evidence of widespread state-sponsored doping in Russia.

Who do we know has been using it?

Since the meldonium ban began on 1 January, Wada has found 99 positive samples amongst athletes who have been tested.

These people include:

  • Olga Abramova of Ukraine, a national team biathlete
  • Abeba Aregawi of Sweden, the 2013 women's 1,500m world champion
  • Ekaterina Bobrova of Russia, an Olympic ice dance champion
  • Maria Sharapova of Russia, women's tennis world number seven
  • Artem Tyshchenko of Ukraine, a European champion biathlete
  • Eduard Vorganov of Russia, a road-race cyclist