pyridoxine /pir′ədok″sēn/ , a water-soluble white crystalline vitamin that is part of the B complex. It is derived from pyridine and converted in the body to pyridoxal and pyridoxamine for synthesis. It functions as a coenzyme essential for the synthesis and breakdown of amino acids, the conversion of tryptophan to niacin, the breakdown of glycogen to glucose 1-phosphate, the production of antibodies, the formation of heme in hemoglobin, the formation of hormones important in brain function, the proper absorption of vitamin B12, the production of hydrochloric acid and magnesium, and the maintenance of the balance of sodium and potassium, which regulates body fluids and the functioning of the nervous and musculoskeletal systems. Rich dietary sources are meats, especially organ meats; whole-grain cereals; soybeans; peanuts; wheat germ; and brewer’s yeast. Milk and green vegetables supply smaller amounts. The most common symptoms of deficiency are seborrheic dermatitis about the eyes, nose, and mouth and behind the ears; cheilosis; glossitis and stomatitis; nervousness; depression; peripheral neuropathy; and lymphopenia, leading to convulsions in infants and anemia in adults. Treatment and prophylaxis consist of administration of the vitamin and a diet rich in foods containing it. Several drugs interfere with the use of pyridoxine, notably isoniazid and penicillamine, and supplements of the vitamin are recommended with the use of these drugs. The need for increased amounts of pyridoxine is related to protein intake and occurs during pregnancy, lactation, exposure to radiation, cardiac failure, aging, and use of oral contraceptives. Also called pyridoxine hydrochloride, vitamin B6.
