To the Editor: Procan SR (Parke–Davis) is a newly marketed sustained-release formulation of procainamide designed to maintain therapeutic plasma concentrations for approximately six hours. According to the package insert, the drug is available as 250-mg (green) or 500-mg (yellow) oval, wax-matrix tablets. Recently we have had reports from several patients who claimed to have observed the presence of what appeared to be intact, undissolved tablets in their stools. We asked the patients to retrieve the tablets for analysis. One patient submitted what appeared to be an undissolved 500-mg tablet that still retained a well-formed oval shape and some of its. . . No extract is available for articles shorter than 400 words.
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