Pharmaceutical Applications of Controlled Release: An Overview of the Past, Present, and Future

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Abstract
The original controlled release pharmaceuticals were coated pills, and they date back over 1000 years to Greco-Roman antiquity. The first coating of pills is recorded in the drug literature of early Islam. Rhazes (850 to 923), recommended mucilage coating of pills using an extract of psyllium seeds while Avicenna (980 to 1037) suggested the silvering and gilding of pills. 1 These coating techniques, and many other Islamic developments in pharmacy and medicine, were adopted in Europe beginning from the 10th century. Thus many of the nobility of Europe, or other persons of wealth, took some of their pills in glittering silver- or gold-coated form. These products were not metalliccoated to provide controlled release, but to mask bitter-tasting agents, to promote swallowing ease, and for appearance sake. These products did, however, undoubtedly alter the release of the “drugs” they contained, as did the “pearl coating” technique which soon followed, where pills were coated with a talc-mucilage composition, producing coated pills resembling pearls. These “pearls” and gold- and silver-coated pills continued to be used through colonial times and into the 19th century, and “pearls” even into the 20th century. You may recall seeing such coated pills in restorations of early American pharmacies or displays of colonial memorabilia. Since talc is not only water insoluble, but is also water repellent, and since gold and silver resist dissolution even in aqua regia, most such products undoubtedly exited the gastrointestinal tracts of their users in substantially the same form in which they were administered, i.e. intact. Considering the crude and impure form, uncertain safety, and questionable efficacy of most drugs of that day, these early coatings may at least have served one use — consumer protection.

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