Digitoxin tablets

Spectrofluorimetry differs from absorption spectrophotometry in not yielding an absolute scale of values. For this reason it is essential to employ a reference standard for quantitative measurements. For example, some pharmacopoeial tests, such as the test for uniformity of content for digitoxin tablets, employ a spectrofluorimefric assay and comparison wi an ofticial reference standard. Quantitative Spectrofluorimetry has been proposed for a munber of naturally fluorescent compoimds, including ergometrine, riboflavine, tiie catechol-amines, phenothiazines, the barbiturates (at pH 13), and certain antibiotics such as chlortetracycline and oxytetracycline. 

Information is very limited, but the interaction seems to be established. It is not likely to occur with solid form, fast-dissolving digoxin preparations (e.g. liquid-filled capsules) or digoxin in liquid form, but only with those preparations which are slowly dissolving (i.e. some tablet formulations). A reduction in digoxin levels of one-third could result in under-digitalisation. There seems to be no information about digitoxin. 

This, the most potent of the digitalis glycosides, is controlled by the B.P,C. on a biological assay, but the U,S.P. relies upon column chromatography followed by application of the alkaline picrate reaction. The same type of assay is also applicable to injection solution and tablets of digitoxin. A suitable method, which has been reported to be satisfactory, is as follows ... 

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