Qualitative and quantitative determination of timolol maleate and dorzolamide hcl in opthalmic solutions

At the present time, timolol maleat and dorzolamide HCl fix combination is used for the treatment of glaucoma.Qualitative and quantitative determinations of this fix combination were carried out using UV Spectrophotometry, high performance liquid chromatography (HPLC) and thin layer chromatography (TLC).Absorbancy ratio method, Vierordt?s method and direct spectrophotometric determination method were used at spectroscopic studies. At absorbancy ratio method, regression equations were derived from the ratio of the absorbances measured at their specific wavelengths (?max) to absorbances measured at isosbestic points. 292 and 252 nm was used as their specific wavelengts and 272,5 and 226 nm was used as isosbestic points. At direct spectrophotometric determination method, 292 nm was used as maximum wavelength of timolol maleate and 252 nm was used as maximum wavelength of dorzolamide hydrochloride.Internal standart method was used at HPLC analysis and hydrochlorothiazide was chosen as internal standart. Ratio of drug substance/internal standart was used for deriving the regression equations and using these equations quantitative analysis of commercial samples was performed.TLC+Spectrophotometry method was performed after making some modifications.Results obtained from these 3 methods were compared and advantages and disadvantages of these methods on timolol maleat-dorzolamide HCl fix combination were defined.Applied methods were compared using Student (t) test and Fisher (F) test. Results obtained from these tests were found non-significant.Results obtained from these methods were found within acceptance criteria and repeatable. The proposed methods were easily applied to pharmaceutical dosage forms.Key words: Timolol maleate, Dorzolamide HCl, Spectroscopic methods, HPLC, TLC, Commercial dosage forms