Laboratory and Clinical Studies with the Riboflavin Antagonist,Galactoflavin. ∗

Summary

1. The riboflavin analog, 10-d-dulcityl-7,8-dimethyl-isoalloxazine (galactoflavin), was absorbed following oral administration to rats and to human patients. Plasma flavin levels and urine flavin excretion were greater in humans than in rodents. 2. Absorbed galactoflavin appeared unchanged in plasma and urine of both species. 3. Maximum absorption of drug was achieved by administration of 1.0 g doses at 8 hour intervals. This dosage was tolerated without undesirable effects for 2 to 5 months by 5 patients. 4. A program of galactoflavin administration in conjunction with a diet calculated to contain less than 0.5 mg riboflavin daily produced clinical signs and symptoms suggestive of riboflavin deficiency in 2 patients and anemia in one patient.