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Developing a single analytical method for estimation of individual drug from a multidrug composition is a very challenging task. A complexation, derivatization, extraction, evaporation, and sensitive-free direct UV spectrophotometric method is developed and validated for the simultaneous estimation of some antiviral drugs such as emtricitabine (EMT), tenofovir disoproxil fumarate (TDF), and rilpivirine HCl (RPV) in tablet dosage form by Vierordt's method. The solutions of standard and sample were prepared in methanol. The λ max⁡ for emtricitabine, tenofovir disoproxil fumarate, and rilpivirine hydrochloride were 240.8 nm, 257.6 nm, and 305.6 nm, respectively. Calibration curves are linear in the concentration ranges 4–12 μg/ml for EMT, 6–18 μg/ml for TDF, and 0.5–1.5 μg/ml for RPV, respectively. Results of analysis of simultaneous equation method were analyzed and validated for various parameters according to ICH guidelines.

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A simple, accurate, rapid, and stability-indicating RP-HPLC method for a combination of tenofovir disoproxil fumarate, emtricitabine, and rilpivirine has been developed and subsequently validated in commercial tablets. The proposed HPLC method utilizes Phenomenex Gemini C18 column (150 mm × 4.6 mm i.d., 5 µm) and mobile phase consisting of MeCN, potassium dihydrogen phosphate buffer (20 mM, pH 3.3), and triethylamine 58.72 : 41.23 : 0.05 (v/v) at a flow rate of 1.7 mL/min. Quantitation was achieved with UV detection at 270 nm. The method was validated in terms of accuracy, precision, linearity, limits of detection, limits of quantitation, and robustness. This optimized method has been successively applied to pharmaceutical formulation and no interference from the tablet excipients was found. TDF, EMT, and RPV and their combination drug product were subjected to acid, base, neutral hydrolysis, oxidation, dry heat, and photolytic stress conditions and the stressed samples were analyzed by the proposed method. As the proposed LC method could effectively separate the drugs from its degradation products, it can be employed as stability-indicating method for the determination of instability of these drugs in bulk and commercial tablets.

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The effect of immune inhibition on the pleomorphism of Trypanosoma brucei was studied by counting trypomastigotes and their granules on agar. A statistical analysis is presented. Busulphan 32 mg/kg, given 24 h before inoculation, caused an inhibition of the infection detectable at 72 h, but not thereafter. Immune inhibition caused by busulphan was associated with increased numbers both of agranular forms and forms containing lipid (type II) granules. After 96 h, treatment did not alter the proportion of agranular to granular forms. The remission was delayed 24 h in treated rats, the remaining trypomastigotes being more sluggish, more fragile and containing more numerous granules of increased size. We conclude that the remission is not produced by the immune reaction but by an innate process of dissolution of the ageing trypomastigotes.