Meldonium (3-(2,2,2-trimethylhydrazinium)propionate; MET-88; quaterine, trade-named as Mildronate) is an antiischemic drug developed at the Latvian Institute of Organic Synthesis. It is a clinically used in the treatment of heart failure, myocardial infarction, arrhythmia, atherosclerosis, and diabetes. Mechanism of action is based on the regulation of energy metabolism pathways through l-carnitine lowering effect. L-Carnitine biosynthesis enzyme γ-butyrobetaine hydroxylase and carnitine/organic cation transporter type 2 (OCTN2) are the main known drug targets of meldonium, and through inhibition of these activities, meldonium induces adaptive changes in the cellular energy homeostasis. Since L-carnitine is involved in the metabolism of fatty acids, the decline in its levels stimulates glucose metabolism and decreases concentrations of l-carnitine related metabolites, such as long-chain acylcarnitines and trimethylamine-N-oxide. Meldonium is used in neurological clinics for the treatment of brain circulation disorders. It appears to improve patients' mood; they become more active, their motor dysfunction decreases, and asthenia, dizziness, and nausea become less pronounced. CNS effects of Meldonium could be mediated by stimulation of the nitric oxide production in the vascular endothelium by modification of the gamma-butyrobetaine and its esters pools. It is hypothesized that mildronate may increase the formation of the gamma-butyrobetaine esters. Meldonium was on the World Anti-Doping Agency’s (WADA) list of drugs being monitored until September 2015, when it was added to the list of banned substances, effective January 1, 2016.