Effect of Isoniazid on Vitamin B6 Metabolism;Its Possible Significance in Producing Isoniazid Neuritis. ∗

Summary and Conclusions

The excretion of an excess of vit. B₆ has been demonstrated in patients receiving isoniazid, with the irregular appearance of abnormal amounts of xanthurenic acid following a test dose of tryptophane. The effect is more marked in those getting a higher dose of INH. Such laboratory evidence of B6 abnormality provides a cause of peripheral neuritis. Preliminary results suggest that the addition of pyridoxine to the high dose of INH prevents neuritis, which otherwise occurs in 40% of the cases.