BARIUM SULFATE SUSPENSIONS.

Abstract

For almost forty years insoluble barium sulfate has been the standard opaque medium used in alimentary tract examinations. During this period many attempts have been made to increase the time during which the barium will stay in suspension. The large number of proprietary products available indicates that the perfect suspens on is yet to be made. Proprietary Preparations A large portion of the annual output of highly purified BaSO4 is processed by adding suspending and flavoring agents—occasionally by grinding, milling, or passing the barium through a colloid mill—and packaging. Few of these proprietary mixtures carry labels that are truly informative. As so ably expressed by Hodges, these “labels appear to have been composed by sales managers rather than chemists or pharmacists and seem calculated to mislead rather than inform” (11). Indeed, the labeling laws of the United States Pure Food and Drug Act do not require that these media be precisely or completely labeled except for the manner in which they vary from U.S.P. barium sulfate. Although patients may be allergic to so-called “inactive ingredients” and receive them both orally and rectally, these substances do not have to be listed on the label as long as the product is administered by a physician for diagnostic purposes. Inquiries to the manufacturer are sometimes ignored, evaded, or, worse, returned with the fallacious statement that no additives are used. When confronted with the evidence that his product must then contain some contaminant, he admits the presence of adjuvants in his barium product, cries “trade secret,” and refuses further information. Processing or manufacturing secrets are of no major concern; the doctor, however, should know what material he is dispensing so that he may guard against allergic reactions and substances that could modify his colleagues' clinical tests. The presence of additives is easily ascertained when the compounds are compared with an equal quantity of pure U.S.P. barium sulfate. Some products become so highly viscous that they must be forced through enema tubing by air pressure or other apparatus. In some suspensions mixed for a shorter time than that recommended by the manufacturer, minute gellike particles float on the surface and stick to the sides of the container. Centrifuging these mixtures at moderate speeds and at intermittent periods reveals a clear or cloudy supernatant fluid that is not pure water. Often several distinct layers reveal the presence of more than one additive. After much correspondence we conclude that many barium manufacturers take the position that they must keep their suspending agents and other additives in the “trade secret” category.