Meldonium is a medication which has been banned by the World Anti-Doping Agency (Wada) since 2016.

The substance was developed in Latvia in 1970 and is used in Eastern European countries to treat cardiac conditions which restrict blood flow around the body.

It cannot be prescribed or purchased in the United Kingdom, but importing it for individual use is not illegal.

The use of meldonium allows blood to be moved more quickly, increasing the body's capacity to carry oxygen. The cardiac benefit, therefore, can in theory lead to better stamina, greater endurance, and increased overall performance for an athlete.

A study, external published in 2015 found that meldonium "demonstrates an increase in endurance performance of athletes, improved rehabilitation after exercise, protection against stress, and enhanced activations of central nervous system functions".

Wada implemented the ban on the use of meldonium by athletes due to mounting evidence that sportspeople around the world were using it to enhance their performance.

A 2015 investigation by Wada at a testing centre in Cologne found that 182 of 8,320 random urine samples gave positive results for the drug - a rate of 2.2%.

Tests at the 2015 European Games in Baku found that 13 medallists were taking the substance at the time.

Wimbledon champion Maria Sharapova failed a drugs test in March 2016 after meldonium was detected in her sample. The Russian claimed she had been taking the substance for a decade to help with health issues and had not noticed that it had been added to Wada's banned list. She was banned for 15 months.

After Sharapova's positive result was announced, Sheffield Hallam University lecturer in forensic science Dr Tom Bassindale told BBC Sport: "[Meldonium] is advertised as giving a mental focus, removing external stress so you feel sharper. There is a slight central nervous system effect, like with stimulants such as caffeine, which gives you a sharper edge.

"It will aid recovery quicker from a hard effort, whether that's playing multiple games of tennis or a cyclist coming back the next day for another stage. There is also an endurance effect."

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