IODINE AND IODIDES IN MEDI CINE. Iodine and its iodides — especially those of sodium and potassium—have been used in medicine since the Chinese are supposed to have introduced them, 2000 B.C. or earlier. The exact method of action of the iodides is not clear, but it would seem that iodine, being a normal constituent of the human body, is a very essential element In normal metabolism. It is found in comparatively large quantities in the thyroid gland, which is known • to exercise a very important action in the general body metabolism, and it is probably by means of the stimulation of the general metabolism of the body that the iodides manifest their beneficial action. The iodides are freely absorbed from watery solutions by mucous membranes throughout the body, particularly in the stomach and intestine. They are taken up into the blood, pass through the tissues, stimulating the lymph flow, and are excreted in the urine in the form of salts. The iodides are likely to irritate the digestive system. Iodine itself possesses a local irritant action. It is soon converted into the iodides when taken internally, and causes similar internal changes.
When the iodides are taken in large doses, or even in small doses for a long time, a form of chronic poisoning known as iodism results. In this the chief symptoms, found in the air passages, consist of a catarrh, especially of the nose, with profuse watery secretion, sneezing and sometimes bronchitis. There is usually
swelling and irritation of the throat and tonsils, and salivation. Nausea and gastric discomforts are common, and skin-eruptions are frequent. There is usually loss of weight, and if the iodide has been taken for a very long period a condition of cachexia, characterized by a great loss of flesh, weakness, depression and restless ness, may result. The chief use of the iodides in medicine is in the treatment of tertiary syphilis, on which it has a specific effect. It is also useful in actinomycosis, metal poisoning, high arterial tension, arteriosclerosis, aortic aneurism, colloid goitre and rheumatic affec tions. k is also very maid' in the various joint-pains of a chronic character, usually known as chronic rheumatism. Iodine is valu able in the treatment of those diseases known to result from thyroid insufficiency, notably in myxcedema (q.v.), and in cretinism, its allied form in children. For stimulation of the respiratory and nasal passages, as in chronic bronchitis, asthma and dry nasal catarrh, the iodides are of great value.