Armour Pharmaceutical is voluntarily recalling 208 lots of H.T. Factorate Antihemophilic Factor, used to treat hemophilia, because six patients who received medication from three of the lots have tested positive for infection with the AIDS virus, according to an announcement by the Food and Drug Administration.

The lots being withdrawn were produced using a heat treatment that may not have killed AIDS virus particles present in the medication, which is made from blood serum from many donors. An FDA spokesman said the company has since changed its method of treatment.

The FDA announcement said that, although the cases involved lots that were distributed only in Canada, all lots manufactured using the previous process are being withdrawn as a precaution. The company said that between 2,000 and 5,000 doses remain on the market in the United States and other countries.

Hemophilia patients who have the product in their homes are advised to check with their doctors to see if it comes from one of the lots being recalled. Affected lots have a six-digit code beginning with A or B and have expiration dates up to December 1988. Not all lots fitting that description are involved.

Physicians, nurses and patients seeking information can call (800) 533-6165, ext. 7070, 7074 or 7077.