Niclosamide Ethanol

Another alternate synthetic method for the manufacturing of niclosamide is reported [1], Phosphorus trichloride (PC13) is slowly introduced into a boiling xylene solution containing 5-chlorosalicylic acid and 2-chloro-4-nitroaniline in equimolar ratio and the heating continued for 3 h. Crystals of niclosamide separate on cooling and are recrystallized from ethanol [7,8], van Tonder et al. [9] prepared and characterized three crystal forms of niclosamide namely the anhydrate and the two monohydrates. 

Niclosamide is practically insoluble in water soluble 1 in 150 of ethanol, 1 in 400 of chloroform, and 1 in 350 of ether sparingly soluble in acetone [4]. 

Selective differential UV spectrophotometric method was presented for the determination of niclosamide in bulk and in its pharmaceuticals [43]. The method was based on measuring niclosamide in alkaline solutions against their neutral ethanolic solutions as blanks. The proposed method was sensitive, highly specific, and advantageous over the conventional UV assays, since the interference of the excipients, impurities, degradation products, or other accompanying drugs was nullified. 

A simple spectrophotmetric method for the determination of niclosamide in bulk and dosage forms was developed [44]. It was based on the reduction of the nitro group in niclosamide to the amino group by treatment with zinc powder and dilute HC1 for 15 min in 95% ethanol solution. The cold and clear filtrate reacted with p-benzoquinone, when a pink compound was obtained which absorbed at 506 nm. 

Liu [51] developed a simple and rapid UV spectrophotometric method for determination of niclosamide. The drug, with or without purification by chromatography on a silica gel plate, was dissolved in anhydrous ethanol and the solution or standard was placed in a 1-cm quartz cell and analyzed at 335 nm by spectrophotometry. 

A spectrophotometric method for the quantitative determination of fenasal (niclosamide) in tablets was given [56]. The tablets were powdered and extracted with acetone at 35-45°C. The solution was treated with ethanolamine in ethanol (1 1) at pH < 8.0 the absorbance was determined at 400 nm. 

Physical Parameters. Niclosamide is obtained as pale yellow crystals having mp 225-230°C. It is found to be practically insoluble in water and sparingly soluble in ethanol, ether and chloroform. 

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