INTRODUCTION:

Atenolol(4-(2-hydroxy-3-isopropylaminopropoxy) phenylacetamide) (ATN),is one of the most used antihypertensive agent^2-4. It showed longer half life and minor side effects than other drugs from β-blocker class. A literature survey revealed different analytical methods for estimation from pharmaceutical dosage forms^5-7. Some bioanalytical methods are also reported for its estimation from biological fluidsas well as bio-equivalence studies were performed^8-12.

Lercanidipine(2-[(3,3-diphenylpropyl)methylamine]-1,1-dimethylethylmethyl1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5 pyridinedicarboxylic ester (LER), is a calcium channel blocker. A literature survey revealed different analytical methods for estimation from its pharmaceutical dosage formsincluding pharmacokinetic studies and stability studies^13-16. The combination therapy of β-blocker and calcium channel blocker becomes often necessary and such dosage forms have been formulated. The present research article reports simultaneous estimation of ATN and LER from its combined tablet formulation. The assay was developed by using isocratic RP-HPLC method

MATERIALS AND METHODS:

Instrument:

Spectrophotometric analysis was carried out on a JASCO UV-spectrophotometer 530 using a 1 cm quartz cell. The instrument settings were zero order and second order derivative mode and band width of 2.0 nm in the range of 200–350 nm.

Reagents and chemicals:

Atenolol and Lercanidipine supplied by Cipla Ltd. India. All solvents were spectrophotometric grade obtained from SD fine chemicals. Water purified by glass distillation apparatus.

Method:

Stock solutions were prepared separately in water: methanol (70:30) to obtain 100 µg/ml of all drug. The nine working mixed standard were prepared by dilution of stock solution in same solvent system in concentration range 5-30 µg/ml of ATN and 5-40 µg/ml for LER. Atenolol and Lercanidipine initially scanned for determining sampling wavelength in range 200-300 nm. Sampling wavelengths 275 nm for ATN where LER showed zero crossing point 322 nm for LER where ATN showed zero crossing point. Calibration graphs were constructed from the absorbances at respective wavelength.

Analysis of commercial formulation:

Content of twenty tablets were taken and powder equivalent to 10 mg of ATN taken and added in 60 ml of solvent system sonicated for 10 min after sonication volume was made up to 100 ml. 1ml of this stock solution was diluted to 10 ml to get concentration equal to 25 µg/ml of ATN and 5 µg/ml of LER. This solution is scanned in range 200-350 nm taking solvent system as blank. The spectra obtained was converted second order derivative spectra absorbances were noted and concentrations were determined from regression equations generated from calibration graph.

TABLE 1: RESULTS OF ANALYSIS OF COMMERCIAL FORMULATION

Analyte	Label claim (mg/tab)	*% Label claim estimated (Mean ± SD)**	RSD*
ATN	50	100.22±0.8722	0.8702
LER	10	100.10±0.8064	0.8055

SD: Standard Deviation, RSD: Relative Standard Deviation.

*Denotes average of six determinations.

TABLE 2: RESULTS OF PRECISION STUDIES

Analyte	Label claim (mg/tab.)	Amount estimated	% label claim ±SD*
ATN	50	50.112	101.12 ± 0.7806
LER	10	10.005	100.10 ± 0.7402

SD: Standard Deviation. *Denotes average of six determinations.

TABLE 3: RESULTS OF RECOVERY STUDIES

Analyte	*% Recovery estimated (Mean ± SD)**	RSD*
ATN	99.10±0.7554	0.7622
LER	100.15±0.8743	0.8729

SD: Standard Deviation, RSD: Relative Standard Deviation.

*Denotes average of six determinations.

RESULTS AND DISCUSSION:

Sampling wavelengths were determined from scanning individual drug samples in 200-350 nm range. Sampling wavelengths were 275 nm and 322 nm for LER and ATN respectively in second order derivative mode. For ATN the concentration in sample solution was calculated by using formula Abs = A + B * C, where A = 0.0002027 and B = 0.0000191, C = concentration of ATN and correlation coefficient was 0.9996. For LER, the concentration in sample solution was calculated by using formula, Abs = A + B * C, where A = 0.00001952, B = 0.00005026, C = concentration of LER and correlation coefficient was 0.9984. Linearity of proposed method was found to be 5-40 µg/ml for LER and 5-30 µg/ml for ATN. Limits of detection were found to be 0.11 µg/ml and 0.31µg/ml of ATN and LER respectively. Results of capsule analysis were reported in table 1, result of precision studies and recovery study reported in table 2 and 3 respectively.

CONCLUSION:

The method used is simple and rapid and does not involve the use of complex instrument, low value of standard deviation showed that the method is precise and high percentage of recovery of as shown in table shows that the method is accurate.

ACKNOWLEDGEMENTS:

Authors are thankful to Cipla Ltd. India, for providing the free gift samples of Atenolol and lercanidipine authors are also thankful to Principal, Bharati Vidyapeeth College of Pharmacy, Kolhapur for providing necessary facilities for this work.

Fig. 1: Overlain spectra of ATN and LER in second order derivative mode.

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