United's England defender was given the ban last Friday after missing a routine test at the club's training ground on September 23. United have indicated they will appeal against the verdict.
"It is a great tragedy that a young player can have a big chunk of his career taken away," said Charlton, a club director, in an interview with United's television channel MUTV.
Ferdinand's ban is not due to start until January 12 and the central defender turned in a solid performance in United's 2-1 league win over Tottenham Hotspur.
"I thought it was faultless when you think he is a young lad who has had all this heat and responsibility heaped on him," Charlton said of Ferdinand's performance at White Hart Lane.
"I thought he was terrific -- he never put a foot wrong, he was solid as a rock."
