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EFFECT OF ULTRA VIOLET RADIATION ON THE STABILITY OF PROGUANIL AND PYRIMETHAMINE
Abstract:
The influence of UV radiation (366nm) on the stability of proguanil hydrochloride and pyrimethamine sulphate in tablet formulations and in phosphate buffer solutions of different pH values has been evaluated in the present study, UV spectroscopic method for estimating drug content in the various dosage forms was employed. The effect of pH on the UV spectrum of the drugs was investigated» The influence of reaction vessel and pH on the irradiated phosphate buffer solutions was also studied, In-vitro dissolution rate studies of the drugs were carried out including those tablets that had been subjected to UV irradiation. The UV spectrum of proguanil hydrochloride was found to be stable at pH values above 2.0 in phosphate buffer solutions. Below pH 2,0 the spectral peak at 232nm disappeared while the peak at 253nm flattened out giving a plateau. Proguanil hydrochloride was found to enter into photochemical reaction in phosphate buffer solution when subjected to continuous UV irradiation at 366nm. Evidence of photochemical reaction was shown by loss of spectral peaks in phosphate buffer, appearance of a precipitate, colour change of solution, spectral shift and increase in absorbance of the irradiated solution. The photochemical reaction was found to be influenced by the pH of the solution and the type of glassware in which the reaction was performed. Assay of irradiated proguanil hydrochloride tablets indicated loss of drug content with time. Dissolution rate studies of the irradiated tablets showed decrease in dissolution rate: with time The UV spectrum of pyrimethamine sulphate remained stable at different Values. Pyrimethamine sulphate appeared not to readily enter into photochemical reaction. The formulations used showed signs of degradation by colour change of tablets but there was no loss of drug content on assay. The dissolution rate of the irradiated pyrimethamine tablets produced by Wellcome Nig. Ltd. increased with time in phosphate buffer solution pH 4.5 while the dissolution rate of irradiated pyrimethamine tablets produced by Quality Control Unit A.B.U. Zaria decreased with time in phosphate buffer solution pH 4.5. This difference observed in the dissolution rates of the formulations has been attributed to the influence of the different excipients used by the different manufacturers.
EFFECT OF ULTRA VIOLET RADIATION ON THE STABILITY OF PROGUANIL AND PYRIMETHAMINE
