Three simple and sensitive spectrophotometric methods (I, II, and III) in the visible region have been developed for the quantitative estimation of nitazoxanide in bulk drug and pharmaceutical formulations. T hese methods are based on the reaction of reduced nitazoxanide with p-dimethylaminobenzaldehyde, p-dimethylaminocinnamaldehyde and vanillin in acidic conditions to form pink, orange red, and orange yellow coloured chromogens with absorption maxima at 559 nm, 534.5 nm, and 475 nm, respectively. The reduction of nitazoxanide was carried out with zinc granules and 5 N hydrochloric acid at room temperature in methanol. Beer’s law is obeyed in the concentration range of 5-25 μg/ml, 5-25 μg/ml, and 10-50 μg/ml, respectively. The results of analysis have been validated statistically and by recovery studies. The methods were found to be accurate, precise, rapid, and economic. The results are comparable with those obtained with visible spectrophotometric method in methanol at 402 nm.

Nitazoxanide (1) 1-5, N-(5-nitro-2-thiazolyl) salicylamide nitazoxanide. acetate, is used as antiprotozoal and anthelmintic agent. It is used in the treatment of giardiasis2 and cryptosporidiasis2. It A Shimadzu UV/Vis double beam spectrophotometer is not official in any pharmacopoeia, and analytical reports(model 1700) with 1 cm matched quartz cells was used for are not found in literature for its quantitative estimation in all spectral measurements. p-dimethylaminobenzaldehyde, bulk drug and pharmaceutical formulations. Three simple p-dimethylaminocinnamaldehyde and vanillin, AR grade, and sensitive spectrophotometric methods for the were obtained from Qualigens, Mumbai. Nitazoxanide quantitative estimation of nitazoxanide have been sample was obtained from M/s Lupin Ltd., Mumbai. developed after converting it to its reduced form, N-(5- Methanol obtained from Qualigens, Mumbai, was used. amino-2-thiazolyl) salicylamide acetate (2), by using zinc granules and 5 N hydrochloric acid in methanol at room About 100 mg of nitazoxanide (pure or equivalent tablet temperature. powder) was accurately weighed and dissolved in 20 ml of methanol. The methanol solution of nitazoxanide was These methods (I, II, and III) are based on the treated with 10 ml of 5 N hydrochloric acid, and 1 g of condensation reaction of reduced nitazoxanide (2) as zinc granules were added in portions while shaking. After shown in Scheme 1 with p-dimethylaminobenzaldehyde standing for 1 h at room temperature, the solution was (PDAB)(3), p-dimethylaminocinnamaldehyde (PDAC)(4), filtered through cotton wool. The residue was washed and vanillin (5) to form pink (6), orange red (7), and with 10 ml portions of methanol three times, and the total orange yellow (8) coloured chromogens with absorption volume of the filtrate was made up to 100 ml with maxima at 559, 534.5 and 475 nm, respectively. Beer’s law methanol. The final concentration of reduced is obeyed in the concentration range of 5-25 μg/ml for nitazoxanide was made to 100 μg/ml. If the methanol methods I and II, and 10-50 μg/ml for method III. These sample solutions were diluted with distilled water, small methods have been successfully extended to the particles were found to appear; therefore, directly pharmaceutical preparations (tablets) containing methanol solutions were used for estimation.