The effect of levodopa may be reduced when vitamin B6 is administered concomitantly.
Pyridoxine-Antagonists eg, Isoniazid, Cycloserine, Penicillamine, Hydralazine: The efficacy of vitamin B6 (pyridoxine) may be decreased.
Loop Diuretics eg, Furosemide: In long-term use, the blood level of thiamine may be reduced.
Long term use of acid lowering agents may lead to Vitamin B12 deficiency.