Several minor changes have been made to the World Anti-Doping Agency (WADA) Prohibited List for 2016, although painkiller Tramadol and Thyroid hormonal medication Thyroxine remain permitted, despite calls for both to be banned.
Among the changes, heart attack drug Meldonium has moved from the monitored to the prohibited list due to “evidence of its use by athletes with the intention of enhancing performance”.
The product, not available in some countries such as the United States, can be used a metabolic enhancer to increase endurance.
Hormone drug Leuprorelin has also been added to the list along with Insulin-mimetics, which is used to treat diabetes.
It was also clarified that blood pressure medication stimulant Clonidine is permitted, along with carbonic anhydrase inhibitors.
Tramadol remains on the monitored list, to which it was first added in 2012, alongside the likes of caffeine and nicotine.
The painkiller, which has side effects including dizziness, drowsiness and nausea, is thought to be particularly popular among cyclists.
In November, Cycling Anti-Doping Commission (CADF) director Francesca Rossi claimed that there would be almost 700 positive tests if Tramadol was banned, Cyclingnews reported.
Others have claimed it has a negligible performance enhancing benefit compared with other products, but could still make a difference of a fraction of a per cent.
Thyroid hormonal medication Thyroxine, meanwhile, will also remain allowed despite an effort from bodies including UK Anti-Doping and the United States Anti-Doping Agency to have it outlawed.
The medication gained prominence last year after it emerged that five runners trained by American coach Alberto Salazar - including Olympic 10,000 metres silver medallist Galen Rupp - had reportedly received treatment for thyroid problems.
It has been exploited by healthy athletes looking to gain an advantage, critics have claimed, citing its benefit in helping shed weight.
"It's so widespread that something needs to be done and it needs properly investigating," claimed Britain's 1991 10,000m world champion Liz McColgan last year.
"There are people out there who are using it and gaining from it and that is a form of cheating."
WADA science director Olivier Rabin disputed these claims, however.
He did reveal, though, that WADA's Expert Committee had considered adding the drug to the list.
“All the experts in the field came to the conclusion that no, there is no way to believe that thyroid hormone could be performance enhancing,” he told the Wall Street Journal, adding that it would also be difficult to standardise legal levels due to significant discrepancies from person to person.
The changes officially came into force on January 1 and come ahead of another big year for WADA, which will face its first milestone on January 14 when the second part of the WADA Independent Commission report on Russian doping in athletics is published.
insidethegames has contacted WADA for further details.