• Amir Khan was banned for two years after an anti-doping test revealed the presence of a banned substance following his fight against Kell Brook in February 2022.
• Joshua has paid for extra testing by the Voluntary Anti-Doping Association for several years to go hand-in-hand with UK Anti-Doping Agency's (Ukad) testing.
Anthony Joshua says boxing "clearly has a problem" with doping after Dillian Whyte failed a voluntary drugs test and was pulled out of Saturday's all-British heavyweight contest.
Joshua, 33, will instead fight Robert Helenius at London's O2 Arena, with the 39-year-old Finnish taking the fight at just a week's notice.
Asked by BBC Sport if boxing has an issue with doping, Joshua said: "I don't know how they're going to sort it out or what their solution is to this problem. But it clearly has a problem."
For the third time in 12 months, boxing is facing serious questions about the sport's credibility and its anti-doping protocols.
In October last year, Conor Benn's bout with Chris Eubank Jr was canceled in fight week after it emerged Benn had failed two voluntary drug tests. Benn has always protested his innocence, as does Whyte.
Amir Khan was banned for two years after an anti-doping test revealed the presence of a banned substance following his fight against Kell Brook in February 2022. The case was not heard by an independent tribunal until January 2023.
On Tuesday it was confirmed Joshua would instead fight Helenius. It is the second time Joshua has had to pull an opponent from a fight due to an anti-doping violation.
In 2019 Andy Ruiz Jr stepped in on a month's notice when American Jarrell Miller tested positive for several banned substances.
Joshua has paid for extra testing by the Voluntary Anti-Doping Association for several years to go hand-in-hand with UK Anti-Doping Agency's (Ukad) testing.
In their latest report, Ukad carried out 213 in-competition tests and 133 out-of-competition tests on fighters connected to the British Boxing Board of Control (BBBoC).
However, in global boxing there is no standardization of anti-doping rules, leading to fighters, like Joshua, choosing to insist on additional steps to provide regular testing.
But Joshua accepts not every fighter has the funds to ensure extra testing and his promoter Eddie Hearn said regular testing below the elite level of boxing is needed.
Hearn, CEO of Matchroom, has been involved with both the Whyte and Benn cases. He promotes both fighters.
Other high-profile athletes to fail tests and serve suspensions include Saul 'Canelo' Alvarez in 2018 and Tyson Fury in 2015 - with both blaming the consumption of suspect meat.
Joshua, however, says he is not surprised by doping scandals in boxing.
"The thing is, people do wonder 'How long has this been going on?'.
"It makes me wonder 'How long has this situation been going on?'. In a way, I'm not shocked anymore in boxing."
The two-time world champion added: "It's not only the belt you're competing for, it's leaving this game with your faculties. Boxing is a dangerous, dangerous game. Even on the side of it where anti-doping is involved, people do take it for granted."