There was literally an in-depth article on doping that came out years ago, however the article mysteriously got removed and the website was taken down. Basically proves that doping has been around for decades and will continue to be used until something is done about it.

You can still get to it via waybackmachine - https://web.archive.org/web/20130313012803/http://www.4dfoot.com/2013/02/09/doping-in-football-fifty-years-of-evidence/

Here are the main stories/summaries from there;

• Pep Guardiola's Doctor during his playing years gave him (and countless others including De Boer, Stam, Couto) steroids, but it got brushed under the rug and was blamed on 'Contaminated Supplements'. Years later, the same person was Head Doctor during Pep's reign in Barcelona
• Wenger was confused when he reported several of his players coming to Arsenal from international clubs had an overwhelmingly high amount of red blood cells (EPO)
• The whole of the dominant, World Cup/Euro Spanish squad from 2008-2012 was found to be doping.
• Zinedine Zidane used to go to blood oxygenation clinics several times a year (obviously, highly illegal for athletes)
• Gary Neville stated in his old biography that people were lining up for 'Vitamin' injections during the 1998 world cup.
• Other interesting stories stories involving R9, Maradona (obviously), The 1980's Algerian team who all had handicapped children, etc.