Reduced vit B
1 efficacy w/ 5-fluorouracil; beverages containing sulphite eg, wine. Diminished vit B
1 uptake w/ antacids; alcohol, black tea. Increased vit B
1 excretion in the urine w/ certain diuretics eg, furosemide. Reduced effect of L-dopa w/ vit B
6. Increased vit B
6 requirement w/ pyridoxine antagonists eg, INH, hydralazine, cycloserine, D-penicillamine.