Tennis players will not be able to plead ignorance if they test positive for banned substances, says the International Tennis Federation.
Maria Sharapova had a two-year ban for taking meldonium cut to 15 months after the Court of Arbitration for Sport (Cas) ruled she was not told about a change in the drug's status.
The Russian tested positive less than a month after meldonium was banned.
The ITF said "appropriate steps were taken to publicise any changes".
However, it said it would continue to review its processes for "communicating changes to the prohibited list to players with the aim of ensuring that no player can claim that they had not been fully informed".
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Sharapova can return to action on 26 April next year because her suspension has been backdated to the date of her first positive test.
The former world number one tested positive for meldonium at the Australian Open on 26 January and again an out-of-competition test on 2 February.
She said she had been taking the drug since 2006 for health reasons and was unaware it had been added to World Anti-Doping Agency's (Wada) banned list as she knew it only by the name mildronate.
However, Cas said Sharapova, a five-time Grand Slam winner, was at fault for not giving her agent "adequate instructions" about Wada's prohibited list and "failing to supervise and control" her agent.
Sharapova's lawyer, John Haggerty, called the Cas decision "a stunning repudiation of the ITF".
He also said the ITF's decision had been exposed as "pure fiction".
He added: "Not only did the tennis anti-doping authorities fail to properly warn Maria, if you compare what the ITF did with how other federations warned athletes of the rule change, it's a night and day difference."
Johan Eliasch, chief executive of racquet manufacturer Head, which has stood by Sharapova during her suspension, said "justice had been served" and called the original ITF decision "wholly unfair".
Eliasch said "there is no doubt Maria broke a rule" but he claims there are inconsistencies in the anti-doping regime and changes are needed.
"This calls into question the revelations about certain Olympic athletes who were granted therapeutic use exemptions (TUEs) for substances that could most certainly be considered performance enhancing and have been proven to be performance enhancing under significant clinical testing," added Eliasch.
"Meldonium has yet to be proven under any significant clinical testing to have any performance enhancing benefits."
Eliasch called for "a wholesale comprehensive review and change to the anti-doping system in identifying performance enhancing drugs".
Former Wimbledon champion Virginia Wade said it was "inexcusable" for Sharapova to find herself in this situation.
However, speaking to BBC Radio 5 live, the Briton added: "She's 100% right. The ITF should be more clear.
"The players need to be much more attentive and you have got to realise that, even if you are trying everything to make yourself feel better, do better, be stronger, that it has to be within the rules."
Pat Cash, the 1987 Wimbledon men's champion, said the 15-month ban was "just a little bit on the lenient side", although he believed Sharapova did not know the drug was banned.
He also accepted that Sharapova had a "fair point" when it came to the ITF.
But the Australian added: "There is no doubt her image has been tarnished. Her reputation will never quite be the same."
BBC tennis correspondent Russell Fuller
"The crux of the matter is that Cas decided it was reasonable for Sharapova to delegate her anti-doping duties to Max Eisenbud and the IMG agency, even if on this occasion those duties were not exercised with remotely enough care.
"Cas has repeatedly set a player's bar of responsibility lower than the ITF think it should be - and as a result there must be a concern some players may in future take anti-doping less seriously than they should."