The anti-doping authority's key witness in its case against the Essendon Football Club's supplements program has been charged with a number of drug-related offences.

Sports biochemist and former bodybuilder Shane Charter was arrested by Purana Taskforce detectives at Melbourne Airport and interviewed in late May.

He has been charged with trafficking and possessing steroids, and possessing a schedule four poison.

Charter is the Australian Sports Anti-Doping Authority's (ASADA) major witness in a separate case against 34 former and current Essendon players.

He is expected to give evidence that players were injected with banned drug Thymosin beta 4.

The 46-year-old has been scheduled to face Melbourne Magistrates Court next week.

The 34 former and current Essendon players were issued with amended show cause notices earlier this month and opted not to respond to them.

The AFL Players Association said it hoped the decision would speed up the process and move a step closer to infraction notices being served.