Drug-Vitamin Interactions
 

Poor vitamin absorption is a common problem with drug administration.

The effectiveness of vitamins ingested not only from supplements, but also from food, can often be deterred by drug ingestion.

One of the most common Drug Nutrient Interactions (DNI's) occurs with the frequent prescription of antibiotics
and the way they can affect the bioavailability of the fat-soluble vitamins (Vitamin A, Vitamin D, Vitamin E, Vitamin K).

Cholestyramine, a drug that is classified as a bile acid sequestrate, can retard the absorption of
Vitamin A, Vitamin D and Vitamin K and bind Essential Fatty Acids as well.


Other interactions between drugs and fat-soluble vitamins include:

*Neomycin can retard absorption Vitamin A, Beta-Carotene

*Ethanol can cause hepatotoxicity resulting in hypervitaminosis A.

*Tetracycline may cause hypertension.

*Vitamin D Cathartics can retard absorption of Vitamin D.

*Glutethimide produces Vitamin D deficiency.

*Vitamin E Dicumarol enhances anticoagulant action.

*Digoxin causes hypercalcemia and arrhythmias

*Vitamin K Anticonvulsants induce enzymatic inactivation.

*Dicumarol inhibits hypoprothrombin action.

Water-soluble vitamins may also be depleted by medication use.

Sometimes it is recommended to ingest the nutrients two hours apart
from the prescribed medication to avoid any interaction.

However, this rule of thumb may depend on the drug.

*Colchicine impairs Vitamin B12 absorption

*Oral contraceptives,
    Hydralazine, Isoniazid and Penicillamine increase the requirement for Vitamin B6.

*Aspirin competes with Folate for serum protein binding.

*Barbiturates cause malabsorption.

*Primadone interferes with Folate metabolism.

*Oral contraceptives cause malabsorption of polyglutamate Vitamin B6

*Cycloserine is secondary to Vitamin B6 antagonism.

*Methotrexate inhibits dihydrofolate reductase.

*Salicylates decrease uptake of Vitamin C.

*Tetracyclines deplete Vitamin C.