"Putting an entrepreneur dealing in medicines on a list for sanctions along with deadly narco-groups is absurd," Karner was quoted as saying in a written statement sent to Slovenian state television.
He added that the substances he sells "are not disputable since they can be bought without a prescription in most states".
The United States on Friday designated six individuals and groups for sanctions, including Karner, freezing their US assets and barring trade with Americans.
The designation means that any assets in the United States may be frozen and any Americans or US companies that try to conduct business with these individuals or groups may be subject to sanctions.
According to US authorities, for the past 10 years Karner has sold anabolic steroids worldwide and set up shell companies in tax havens to conceal millions of dollars in drug profits.
Karner, his wife and his brother were indicted in Massachusetts federal court in 2010 on three counts of money laundering conspiracy and distributing and importing steroids.
He and his wife were arrested and detained in Austria in December 2010, but were released on bail in April 2012 while fighting extradition and then fled to their native Slovenia, which has no extradition treaty with the United States, according to the Treasury.
Slovenian television confirmed that Karner was in Slovenia and he had said the sanctions represented additional pressure from Washington ahead of an expected ruling by the European Court of Human Rights on an appeal he filed against his extradition.
"Karner is convinced the European court will not allow his extradition to the US since the punishment for illegal substances trafficking there -- up to 40 years in prison -- is much higher than in Europe, where it is up to three years," the broadcaster reported.