Meldonium (Mildronate) is a drug manufactured in Latvia since the 1980’s where it is legal, however the FDA has not approved it for use in the US.
tennis
It is an ‘anti-ischemic’ drug, which means it is used to treat inadequate blood-flow to the organs, especially the heart. It is primarily used to treat patients with heart conditions that affects the body’s ability to deliver oxygen to the body.  It helps to protect against tissue damage from angina attacks, chronic heart failure and disorders of brain circulation.
Due to its ability to increase oxygen uptake it is also beneficial to healthy individuals and athletes as it increases mental function and physical capacity and stamina. This is why it was banned by the anti-doping authorities at the beginning of the year and caught out a number of athletes who have tested positive, such as the tennis player Maria Sharapova.
Meldonium reduces the amount of oxygen that is needed to keep tissues alive by changing the way the muscle cells metabolize substances in the blood. It alters the mitochondria to utilize carbohydrates for energy instead of fatty acids, a process which requires less oxygen to carry out. Therefore in people with less oxygen in their blood they can still produce energy in the cells and the tissue and organs remain healthy. In athletes this reduction for the need of oxygen can enhance their performance. During exercise our bodies use oxygen at a faster rate than the lungs can replace it but this drug can reduce the amount of oxygen being used up allowing athletes to work out for longer. Processing carbohydrates instead of fatty acids also means that there is less lactate and urea produced, which would normally cause stiffness and pain in the muscles after a workout and so an athlete can workout out for longer and more frequently. Due to its ability to allow an athlete to work out more efficiently and for longer by altering the way the cells metabolize substances for energy, and diminishing the need for oxygen it has been considered as an unfair advantage over other athletes and has been banned.
The drug however has other benefits and in combination with other drugs can help treat diabetes as it reduces the amount of glucose in the blood due to making the cells process carbohydrates which contain glucose molecules.  It can also improve mood and motor functions in patients with neurological disorders and brain circulatory problems as well as enhancing cognitive ability and reducing dementia.
The drug is being considered as a possible addition to the treatment plan for patients suffering from respiratory conditions such as COPD. These patients can suffer from very low oxygen levels in their blood and be on supplemental oxygen therapy to try and combat this and they feel very weak and tired due to the low oxygen. Meldonium could allow the body to allocate less oxygen to the cells for energy metabolism and redirect it elsewhere where it is also needed. Patients would benefit from increased oxygen levels in their blood and feeling less fatigued which could help curb the progression of the disease. These patients are advised to stay fit and healthy and to exercise as much as possible. With the benefits seen with this drug being used by athletes then the same could apply to these patients and allow them to exercise for longer, which would also benefit their health.
References: www.techinsider.io and http://qz.com