Serum pyridoxal in patients with rheumatoid arthritis.

Abnormalities of tryptophan metabolism have been reported in patients with rheumatoid arthritis (RA) and it has been suggested that these abnormalities are the result of disordered vitamin B6 metabolism. Fasting serum pyridoxal, assayed by an automated microbiological system, was found to be below normal in 35 out of 42 patients with RA while a similar abnormality was found in 8 out of 35 patients with osteoarthrosis (OA). Within the RA group the abnormality could not be related to the age, sex, or drug therapy of individuals but of the 8 patients with OA and a low serum pyridoxal, 7 were receiving indomethacin either alone or in conjunction with aspirin.