Chronic use of loop diuretics may result in thiamine deficiency. Substances in food (eg, sulfite, caffeine) may inactivate thiamine. Although the clinical importance is unknown, thiamine reportedly may enhance the effect of neuromuscular-blocking agents.
Probenecid may inhibit the absorption and renal tubular secretion of riboflavin. Use of oral contraceptives may result in decreased serum levels of riboflavin.
Women, who are taking folic acid supplements, especially if they are current or former users of oral contraceptives, are at risk for lower plasma zinc concentrations.
The use of oral contraceptives may increase vitamin B6 requirements. Chronic and excessive use of alcoholic beverages can result in vitamin B6 deficiency.
Metformin may decrease the absorption of vitamin B12. This possible effect may be reversed with oral calcium supplementation. Folic acid may work synergistically with vitamin B12 in lowering homocysteine levels.
Supplementary vitamin D should be used cautiously in those on digoxin or any cardiac glycoside. Hypercalcemia in those on digoxin may precipitate cardiac arrhythmias.
Broad-spectrum antibiotics may sterilize the bowel and decrease the vitamin K1 contribution to the body by the intestinal microflora. Cephalosporins containing side chains of N-methylthiotetrazole or methylthiadozole can cause vitamin K deficiency and hypoprothrombinemia.
Vitamin K1 can antagonize the effect of warfarin; therefore, the use of warfarin should be avoided, unless specifically prescribed by the physician.
Antibiotics may decrease biotin contribution to the body made by the microflora of the large intestine.
No interactions between DHA and aspirin, other NSAIDs or herbs eg, Allium sativum (garlic) have been reported. If such interactions were to occur, it might be manifested by nosebleeds and increased susceptibility to bruising.