Is brewer's yeast for medical use permissible or forbidden?

The well-known yeast used to leaven bread is permissible (halal), because it does not intoxicate and does not contain alcohol. However, if the yeast is made from intoxicants (khamr) or mixed with an intoxicant, its ruling is the same as that of an intoxicant: "whatever intoxicates in large quantities, a small quantity of it is unlawful (haram)." As for its medical use, physicians should be consulted, and if it poses no health risk, contains no alcohol, and does not lead to intoxication, then there is no objection to its use.