Aromatic amines and the pathogenesis of lupus erythematosus.

The acetylation pathway of drug metabolism is the pathway by which aromatic amines and hydrazines are metabolized. Hydralazine and procainamide are aromatic amines or hydrazines that are metabolized by this pathway. Persons who are genetically slow acetylators are predisposed to development of lupus from these two drugs, suggesting that the free amine or hydrazine moiety is the inciting agent. When acetylprocainamide was given as an antiarrhythmic drug to patients with procainamide-induced lupus, the disease went into remission, indicating that the free amine group on procainamide had induced the disease. The genetic acetylator phenotypes of persons with idiopathic lupus were studied, and an excess of genetic slow acetylators was observed. This suggests amines or hydrazines induce some cases of this disease. One patient was identified with a lupus-like illness due to occupational exposure to hydrazine itself.