Development and Validation of Spectroscopic Method for Simultaneous Determination of Theophylline and Etofylline in Pharmaceutical Dosage Form

Two novel, simple, accurate, precise, sensitive, economical and rapid UV spectrophotometric methods have been developed for simultaneous estimation of Theophylline (TH) and Etofylline (ETH) in combined tablet dosage form. From solvent effect studies and the spectral behaviors of TH and ETH, 5% w/v NaOH was selected as solvent. The Method A employs estimation of drugs by simultaneous equation method (SEM) using 243.5 and 275.0 nm i.e. λmax values of ETH and TH respectively. Method B employs the estimation of drugs by Absorption Ratio method (ARM) at 275 i.e. λmax values of one drug and 254.5 nm an isoabsorptive wavelength. TH and ETH individually and in mixture follow Beer's law over the concentration range 5–25 μg/ml at all the selected wavelengths. Additivity study concluded that both the drugs do not interact with each other in solution. The percent recoveries of the drugs were found nearly 100% representing the accuracy of the both methods. Validation of the proposed methods was carried out for its accuracy, precision, specificity, linearity and range, ruggedness, limit of detection according to ICH guidelines. The proposed methods can be successfully applied in routine work for the determination of Theophylline and Etofylline in combined tablet dosage form.