Development and Validation of Spectrophotometric Methods for Simultaneous Estimation of Valsartan and Hydrochlorothiazide in Tablet Dosage Form

Two UV-spectrophotometric methods have been developed and validated for simultaneous estimation of valsartan and hydrochlorothiazide in a tablet dosage form. The first method employed solving of simultaneous equations based on the measurement of absorbance at two wavelengths, 249.4？nm and 272.6？nm, for valsartan and hydrochlorothiazide, respectively. The second method was absorbance ratio method, which involves formation of Q-absorbance equation at 258.4？nm (isoabsorptive point) and also at 272.6？nm ( of hydrochlorothiazide). The methods were found to be linear between the range of 5–30？μg/mL for valsartan and 4–24？μg/mL for hydrochlorothiazide using 0.1？N NaOH as solvent. The mean percentage recovery was found to be 100.20% and 100.19% for the simultaneous equation method and 98.56% and 97.96% for the absorbance ratio method, for valsartan and hydrochlorothiazide, respectively, at three different levels of standard additions. The precision (intraday, interday) of methods was found within limits ( ). It could be concluded from the results obtained in the present investigation that the two methods for simultaneous estimation of valsartan and hydrochlorothiazide in tablet dosage form are simple, rapid, accurate, precise and economical and can be used, successfully, in the quality control of pharmaceutical formulations and other routine laboratory analysis. 1. Introduction Valsartan (VAL) (Figure 1), a nonpeptide, is N-(1-oxopentyl)-N-[[2′-(1H-tetrazol-5-yl) [1,1′-biphenyl]-4-yl] methyl]-L-valine [1]. It is a potent, highly selective, orally active, specific angiotensin II receptor antagonist used as a hypotensive drug. Hydrochlorothiazide (HCT) (Figure 2) is 6-chloro-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulphonamide,1,1-dioxide, which is a diuretic drug [2]. In patients with moderate hypertension, first-line therapy with the fixed-dose of valsartan/hydrochlorothiazide combination leads to BP normalization with high response rates. The rationale behind this drug combination is that in treatment of hypertension in patients whose blood pressure is not adequately controlled by monotherapy, oral administration of valsartan with hydrochlorothiazide has been found more effective than the use of either drug alone [3, 4]. Very few methods for determination of valsartan and hydrochlorothiazide in tablet dosage form have appeared in the literature. A liquid chromatography/tandem mass spectrometry method includes protein precipitation using acetonitrile and the analytes were separated on a Zorbax SB-Aq C18 column using acetonitrile ？10？mM ammonium acetate