HPLC Assay and Stability Studies of Tablets Containing Paracetamol and Caffeine

A high-performance liquid chromatography analytical procedure for the simultaneous determination of paracetamol and caffeine in a model tablet formulation has been developed. The separation was achieved on a C8 column at a flow rate of 1.0 ml/min with UV detection at 230 nm. The mobile phase was composed of 1mM phosphate buffer pH 7.0 – methanol (65:35 v/v). The method was validated through investigation of analytical parameters such as specificity, linearity, precision, accuracy, LOD and LOQ. The linearity of the method was investigated in the concentration ranges 31.25-250 μg/ml (r = 0.9999) for paracetamol and 4.06-32.50 μg/ml (r = 0.9998) for caffeine. The method was found to be accurate, with recoveries in the range 99.57% – 99.87%. Stability studies of a model tablet formulation containing 500 mg paracetamol and 65 mg caffeine were carried out at 25 ± 2oC and RH = 60 ± 5% (long term storage), for one year, and at 40 ± 2oC and RH = 75 ± 5% (accelerated storage). Essential physical-chemical properties of the tablets were evaluated such as: mechanical strength, disintegration time, drug release kinetics and drug content. No significant changes were found in any of the evaluated tablet characteristics. It was established that the produced tablets possess good stability characteristics which allows to proceed to clinical evaluation and scale up of the product.