Metformin, omeprazole, and colchicine can all interfere with the absorption of vitamin B12. Metformin can decrease the absorption of vitamin B12 in the small intestine, while omeprazole and colchicine can interfere with the absorption of vitamin B12 in the stomach.

Vitamin K is a cofactor for the enzyme that converts warfarin to its inactive form. Therefore, high intake of vitamin K can decrease the effectiveness of warfarin.

Thiazide diuretics can increase the excretion of potassium by inhibiting the reabsorption of potassium in the kidneys.

Alcohol can interfere with the metabolism of warfarin and increase the risk of bleeding.

Tetracycline, ciprofloxacin, and calcium supplements can all interfere with the absorption of iron. Tetracycline and ciprofloxacin can chelate iron and prevent its absorption in the small intestine, while calcium supplements can bind to iron and form insoluble complexes that are not absorbed.

Vitamin D, vitamin C, and folic acid can all interfere with the metabolism of phenytoin. Vitamin D can increase the metabolism of phenytoin, while vitamin C and folic acid can decrease the metabolism of phenytoin.

Loop diuretics can increase the excretion of calcium by inhibiting the reabsorption of calcium in the kidneys.

Alcohol can interfere with the metabolism of glucocorticoids and increase the risk of bone loss.

Methotrexate, sulfasalazine, and trimethoprim can all interfere with the absorption of folate. Methotrexate and sulfasalazine can inhibit the transport of folate across the intestinal mucosa, while trimethoprim can interfere with the metabolism of folate.

Folic acid is a cofactor for the enzyme that converts methotrexate to its inactive form. Therefore, high intake of folic acid can decrease the effectiveness of methotrexate.

Loop diuretics can increase the excretion of magnesium by inhibiting the reabsorption of magnesium in the kidneys.

Grapefruit juice can interfere with the metabolism of statins and increase the risk of muscle weakness.

Mineral oil, orlistat, and cholestyramine can all interfere with the absorption of vitamin A. Mineral oil can prevent the absorption of vitamin A in the small intestine, while orlistat and cholestyramine can bind to vitamin A and prevent its absorption.

Grapefruit juice, St. John's wort, and garlic can all interfere with the metabolism of cyclosporine. Grapefruit juice and St. John's wort can increase the metabolism of cyclosporine, while garlic can decrease the metabolism of cyclosporine.

Penicillamine, furosemide, and hydrochlorothiazide can all increase the excretion of zinc. Penicillamine can chelate zinc and increase its excretion in the urine, while furosemide and hydrochlorothiazide can increase the excretion of zinc in the urine by inhibiting its reabsorption in the kidneys.