The federal agency said 6-OXO (4-androstene-3,6,17-trione) and 1-AD (1-androstenediol), or any other supplements containing similar ingredients can potentially cause serious medical conditions.

Both 6-OXO and 1-AD -- manufactured by ErgoPharm-Proviant Technologies in Champaign, Ill. -- are promoted as dietary supplements for body building, and aren't authorized for sale in Canada. Health Canada said it received one adverse reaction case report, in which an individual developed seizures and blood clots in his brain, associated with use of the products.

Health Canada said 6-OXO is an unauthorized natural health product in Canada, while 1-AD is regulated as a controlled substance in Canada, meaning it should only be dispensed by prescription. While neither product is authorized for sale in Canada, Canadians can access them on the Internet or purchase them while traveling abroad.

Officials said Canadians should contact the Health Products and Food Branch Inspectorate at 800-267-9675 if they find 6-OXO or 1-AD or any other supplements containing 4-androstene-3,6,17-trione, or 1-androstenediol being sold at a Canadian retail outlet without a prescription.