Microzide
Simultaneous determination of fosinopril and hydrochlorothiazide in pharmaceutical formulations by spectrophotometric methods.

Erk N.

Department of Analytical Chemistry, Faculty of Pharmacy, University of Ankara, 06100 Ankara, Turkey. erk pharmacy.ankara.edu.tr

Three new spectrophotometric procedures for the simultaneous determination of fosinopril and hydrochlorothiazide are described. The first method, derivative-differential spectrophotometry, comprised of measurement of the difference absorptivities derivatized in the first-order (DeltaD(1)) of a tablet extract in 0.1 N NaOH relative to that of an equimolar solution in methanol at wavelengths of 227.6 and 276.4 nm, respectively. The second method, depends on the application ratio spectra derivative spectrophotometric method to resolve the interferance due to spectral overlapping. The analytical signals were measured at 237.9, 243.8 nm for fosinopril and 262.4, 269.3 and 278.6 nm for hydrochlorothiazide in the binary mixture, in the first derivative of the ratio spectra of the mixture solutions in methanol. Calibration graphs were established for 4.0-50.0 microg ml(-1) fosinopril and 2.0-14.0 microg ml(-1) hydrochlorothiazide in binary mixture. The third method, absorbance ratio method, the determination of fosinopril and hydrochlorothiazide was performed by using the absorbances read at 210.0, 219.5 and 271.7 nm in the zero-order spectra of their mixture. The developed methods were compared with absorbance ratio method. Application of the suggested procedures were successfully applied to the determination of this compound in synthetic mixtures and in pharmaceutical preparations, with high percentage of recovery, good accuracy and precision.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11836054&dopt=Abstract hydrochlorothiazide Microzide



Microzide
A stability-indicating LC method for the simultaneous determination of ramipril and hydrochlorothiazide in dosage forms.

Belal F, Al-Zaagi IA, Gadkariem EA, Abounassif MA.

Department of P armaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia. ffbelal ksu.edu.sa

A simple, rapid and sensitive HPLC method has been developed for the simultaneous determination of ramipril and hydrochlorothiazide in their dosage forms. Acetonitrile: sodium perchlorate solution (0.1 M) adjusted to pH 2.5+/-0.2 with phosphoric acid (46:54 v/v), was used as the mobile phase, at a flow rate of 1.5 ml/min. A supelcosil LC-8 column (5 microm), 15 cm x 4.6 mm i.d. was utilized as stationary phase. Detection was affected spectrophotometrically at 210 nm. Clobazam was used as an internal standard. The method was also applied for the determination of ramipril in the presence of its degradation products. Linearity ranges for ramipril and hydrochlorothiazide were 4.5-45 and 0.6-14 microg/ml, respectively. Minimum detection limits (S/N = 2) obtained were 180 and 23 ng/ml for ramipril and hydrochlorothiazide, respectively. The proposed method was further applied to the analysis of tablets containing the two drugs, the percentage recoveries +/- S.D. (n = 5) were 100.45%+/-0.63 and 99.55%+/-0.78 for ramipril and hydrochlorothiazide, respectively.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11199212&dopt=Abstract hydrochlorothiazide Microzide



Microzide
Predictors of antihypertensive response to a standard dose of hydrochlorothiazide for essential hypertension.

Chapman AB, Schwartz GL, Boerwinkle E, Turner ST.

Renal Division, Department of Medicine, Emory University School of Medicine, 1639 Pierce Drive, Atlanta, GA 30322, USA. arlene_chapman emory.org

BACKGROUND: Determinants of inter-individual variation in blood pressure (BP) response to antihypertensive therapy remain largely unknown. Although differences in race, age and measures of the renin-angiotensin-aldosterone system (RAAS) have been associated with variation in blood pressure response to hydrochlorothiazide, whether these characteristics make additive contributions to predicting response has not been established. We conducted a comprehensive search for predictors of BP response to a standard dose of hydrochlorothiazide in a biracial sample to estimate how much inter-individual variation in BP response could be explained by all of the identified predictors. METHODS: After withdrawal of antihypertensive medications for at least four weeks (baseline) and stabilization on a diet approximating 150 mmol sodium per day, 225 African American and 280 Caucasian subjects with diagnosed essential hypertension were treated for four weeks with hydrochlorothiazide 25 mg per day. At baseline and the end of treatment, subjects were admitted to the General Clinical Research Center for measurement of activity of the RAAS and other regulators of BP. Characteristics measured at study enrollment, at baseline, and in response to drug treatment were incorporated stepwise into linear regression models in order to quantify their additive contributions to predicting BP responses to hydrochlorothiazide. RESULTS: Black race and female gender were both associated with significantly greater systolic (SBP) and diastolic (DBP) blood pressure responses to hydrochlorothiazide. Together the combined effects of race and gender accounted for 11% inter-individual variation in SBP response (P < 0.0001) and 4% of inter-individual variation in DBP response (P < 0.0001). Additional statistically significant predictors of greater systolic and diastolic responses to hydrochlorothiazide included, shorter duration of diagnosed or treated hypertension (P < 0.001), higher baseline BP level (P < 0.0001), lower baseline plasma renin activity (P < 0.05), lower baseline urinary aldosterone excretion (P < 0.002), and greater decrease in urinary sodium excretion (P < or = 0.004). Greater decrease in weight was an additional statistically significant predictor of SBP but not DBP response, and older age was a predictor of diastolic but not SBP response. The combined effects of all identified predictors accounted for 38% of inter-individual variation in SBP response (P < 0.0001) and 20% of inter-individual variation in DBP response (P < 0.0001). CONCLUSIONS: A systematic search reveals numerous predictors of BP response to a standard antihypertensive dose of hydrochlorothiazide. However, because the majority of inter-individual variation in SBP and DBP responses remains unexplained, there is considerable opportunity for future investigations to improve the ability to predict individual BP responses to antihypertensive drug therapy.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11849460&dopt=Abstract hydrochlorothiazide Microzide



Microzide
The use of a response surface methodology on HPLC analysis of methyldopa, amiloride and hydrochlorothiazide in tablets.

Zecevic M, Zivanovic L, Agatonovic-Kustrin S, Minic D.

Institute of Pharmaceutical Chemistry and Drug Analysis, Faculty of Pharmacy, Vojvode Stepe 450, 11000 Belgrade, Serbia, Yugoslavia.

A multifactor optimisation technique is successfully applied to develop a new HPLC method in which methyldopa, hydrochlorothiazide and amiloride were analysed and determined on a C18 column with detection at 286 nm. The optimal conditions of HPLC separation were determined with the aid of the response surface diagram -- 'window diagram'. The effect of simultaneously varying the pH, proportion aqueous acetic acidum and methanol in the mobile phase were studied to optimise the separation. The mobile phase composition that provides an acceptable resolution methyldopa, hydrochlorothiazide and amiloride in a short elution time is water--methanol (75:25) and pH 3.60. The k' values for methyldopa, hydrochlorothiazide and amiloride after optimisation were 1.40, 2.50 and 5.33, respectively. Relative retention (alpha) for ratio hydrochlorothiazide/methyldopa and amiloride/hydrochlorothiazide were 1.767 and 2.159, respectively. Correlation coefficients of the calibration curves for all analytes were greater than 0.995 and the R.S.D. values for the slope and the intercept with respect to the linearity were less than 2%. A method is applied for the quantitative analysis of Alatan tablets (Lek-Ljubljana). The powdered tablets are extracted with methanol, containing caffeine as the internal standard and assayed by comparison of peak areas after liquid chromatography. The high recovery (for all analytes about 100%) and the low R.S.D. (<2%) confirm good precision and reproducibility of the chromatographic method.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11248497&dopt=Abstract hydrochlorothiazide Microzide



Microzide
Effects of perindopril, propranolol, and dihydrochlorothiazide on cardiovascular remodelling in spontaneously hypertensive rats.

Su JZ, Chen SC, Wu KG, Chen DG, Rui HB, Wang XY, Wang HJ.

Department of Cardiology, First Affiliated Hospital of Fujian Medical University, Fujian Institute of Hypertension Research, Fuzhou 350005, China. sujinzi 163.net

AIM: To investigate the effects of perindopril, propranolol, and dihydrochlorothiazide on artery wall thickening, left ventricular hypertrophy, and cardiac fibrosis in spontaneously hypertensive rats (SHR). METHODS: After measurement of systolic blood pressure (SBP), 16-wk-old Male SHR were randomly divided into 3 groups (each n = 10), given perindopril (Per, 5 mg.kg-1.d-1), propranolol (Pro, 40 mg.kg-1.d-1), dihydrochlorothiazide (DCT, 100 mg.kg-1.d-1) respectively by gavage for 12 wk. Sex-, age-, and number-matched untreated SHR and normotensive Wistar Kyoto rats (WKY) served as controls. When the treatment finished, body weights (BW) and SBP were measured before decapitation of the rats. The heart was excised rapidly, the left ventricle was weighed and then subjected to collagen content analysis. Vascular wall and lumen ratio from aorta, renal arteries and branch III vessels of mesenteric arteries were determined morphometrically. RESULTS: Treated rats in 3 groups showed a lower SBP and the ratio of left ventricle weight to body weight (LVW/BW) compared with WKY. Artery wall thickening was similarly inhibited in the treated groups. Per and Pro inhibited cardiac fibrosis, but collagen concentration increased in DCT treated SHR [collagen volume fraction (CVF): 19 +/- 4 vs SHR 14 +/- 4, P < 0.05; perivascular collagen fraction(PVCF): 84 +/- 7 vs SHR 79 +/- 5, P < 0.05]. CONCLUSION: Per and Pro inhibited, but DCT promoted, cardiac fibrosis.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11270993&dopt=Abstract hydrochlorothiazide Microzide