Development and Validation of HPTLC Method for Simultaneous Estimation of Atorvastatin Calcium and Olmesartan Medoxomil in Tablet Dosage Form

About Author:
D. J. Kalena*, C. N. Patel
Department of Quality Assurance,
Shri Sarvajanik Pharmacy College,

Near arvind baug, Mehsana - 384 001, Gujarat, India

A simple, precise, accurate and rapid high performance thin layer chromatographic method has been developed and validated for the simultaneous estimation of atorvastatin calcium and olmesartan medoxomil in combined dosage forms. The stationary phase used was TLC aluminium plate precoated with silica gel 60F254. The mobile phase used was a mixture of acetonitrile: chloroform: methanol: 10% glacial acetic acid (7: 2: 1.5: 0.1 v/v/v/v). The system was found to give compact spot for both atorvastatin and olmesartan (Rf value 0.5±0.01 and 0.76±0.02 respectively). The densitometric analysis of spot was carried out in reflectance mode at 253 nm. The method was validated in terms of linearity, specificity, precision, robustness and accuracy. The calibration curve was found to be linear in the range of 200 to 800 ng/spot for atorvastatin and 400 to 1600 ng/spot for olmesartan. The limit of detection and the limit of quantification for the atorvastatin were found to be 178.239 and 540.11 ng/spot and for olmesartan 40.10 and 121.51 ng/spot, respectively. The proposed method can be successfully used to determine the drug content of marketed tablet formulation.

REFERENCE ID: PHARMATUTOR-ART-1143

Atorvastatin calcium (AT), [R- (R*, R*)]-2-(4-fluorophenyl)-β, δ-dihydroxy-5-(1 Methyl ethyl)-3-phenyl-4-[(phenyl amino) carbonyl] 1Hpyrrole-1-heptanoic acid, calcium salt (2:1) trihydrate [Figure 1], is a white crystalline powder, slightly soluble in water and ethanol and freely soluble in methanol. AT is a HMG-CoA reductase inhibitor. HMG-CoA reductase catalyzes the reduction of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) to mevalonate, which is the rate-limiting step in hepatic cholesterol biosynthesis[1, 2]. It is official in Indian pharmacopoeia[3]. Olmesartan medoxomil (OLM), [2, 3-dihydroxy-2-butenyl 4-(1-hydroxy-1-methyl ethyl) -2-propyl- 1-[p-(o-1H-tetrazol-5-yl phenyl) benzyl] imidazole-5-carboxylate, cyclic 2, 3-carbonate] [Figure 2] is a white to yellow white crystalline powder, insoluble in water and sparingly soluble in methanol. OLM is an angiotensin II receptor blocker (ARB). It blocks the vasoconstrictor effects of angiotensin II by selectively blocking the binding of angiotensin II to the AT1 receptor in vascular smooth muscle[4, 5].

Tablet dosage forms containing AT and OLM in ratio of 10mg and 20 mg is newly approved combination by Central Drug Standard Control Organization (CDSCO) for marketing in India for the treatment of coexisting essential hypertension and hyperlipidemia in adult persons in October 2009. Several analytical methods that have been reported for the estimation of AT in biological fluids and/or pharmaceutical formulations include spectrophotometric[6, 7], high performance liquid chromatography[8-10] and high-performance thin layer chromatography[11], while OLM determinations have been reported by UV?Vis spectrophotometry [12-14], HPLC [15-18] and HPTLC [19, 20]. However there is no method available for the simultaneous determination of AT and OLM in combined fixed dosage form. Therefore, an attempt was made to develop a rapid, economic and sensitive method for the simultaneous determination of AT and OLM. To access the reproducibility and wide applicability of the developed method, it was validated as per ICH norm, which is mandatory also[21, 22].

MATERIAL AND METHODS
Materials:

Working standards of AT and OLM were procured as gift sample from Sun pharmaceuticals Ltd. Baroda. Silica gel 60F254 TLC plate (20×20 cm, layer thickness 0.2 mm, Merck, Mumbai) was used as a stationary phase. All chemicals and reagent used were of analytical grade. Tablet containing AT (10mg) and OM (20mg) were procured from local pharmacy store (Olmesar-AV, Macleod pharma).

Instrumentation:
Chromatographic separation of drugs was performed on Merck TLC plates precoated with silica gel 60 F254 (20×20 cm, with 0.2 mm layer thickness). The samples were applied onto the plates as a band with 5 mm width using Desaga 100 μl sample syringe (Hamilton, Switzerland) with an AS-30 sample applicator (Desaga, Switzerland). Linear ascending development was carried out in a twin trough glass chamber (for 10x10 cm). Densitometric scanning was performed using Densitometer CD-60 TLC scanner (Desaga) in the range of 200- 400 nm and operated by proquant software (Desaga).

Standard preparation:
Standard stock solution of 1000 µg/ml of AT and OLM were prepared in methanol. Mix Working standard were prepared by taking dilution ranging from 20-80 µg/ml of AT and 40-160 µg/ml of OLM. This solution were used for linearity range

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