A novel stability-indicating high performance liquid chromatographic method (HPLC) was developed and validated for the quantitative determination of carvedilol (CAR) and hydrochlorothiazide (HCTZ) in bulk powders and in combined tablet dosage form. In the literatures there is only one reported stability-indicating HPLC method for the simultaneous determination of carvedilol and hydrochorothiazide, in which each drug was analyzed and separated in the presence of its degradants but not in the presence of other drug degradants. In the proposed method both drugs could be separated from each other and in the presence of degradants of the other drug. An isocratic HPLC method, using a C-18 reversed phase column with a mobile phase composed of 50 mM potassium dihydrogen phosphate and acetonitrile (ACN) (68:32, v/v) was developed to separate the drugs from their stress degradants. The flow rate was 1 mLmin-1 and the detection was performed at 220 nm. Limit of detection and limit of quantification for carvedilol were 3.3 and 10 μg mL-1 while they were 2.5 and 7.5 μgmL-1, respectively, for hydrochlorothiazide. Clear degradation was observed in acidic conditions for carvedilol, and in both acidic and alkaline conditions for hydrochlorothiazide. Percentage recoveries of the mixture in tablets ranged from 97.20% to 99.71% and from 99.74% to 101.34 for carvedilol and hydrochlorothiazide, respectively. Forced degradation studies were performed to prove the stability-indicating power of the method.
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