INTRODUCTION:

Lansoprazole Lansoprazole as shown in Figure 2 is chemically 2-({[3-methyl-4-(2, 2, 2-trifluoroethoxy) pyridin-2-yl] methane} sulfinyl)-1H-1, 3-benzodiazole. It is a potent Proton Pump Inhibitor used in acidity, ulcers, Gastro-esophageal Reflux Disease, etc. BP 2009 includes potentiometric estimation of Lansoprazole while USP 2007 and IP 2014 include a Liquid chromatographic method for assay of Lansoprazole ⁴. Aspirin in pharmaceutical dosage form^2,11-18. Extensive literature survey reveals, only one UV method is available for simultaneous estimation of Lansoprazole and Aspirin in their combined dosage form²³.

Aim of present work was to develop simple, precise, accurate and economical spectrophotometric methods for simultaneous determination of Lansoprazole and Aspirin in their combined dosage form. The proposed method was optimized and validated in accordance with International Conference on Harmonization (ICH) guidelines. Literature survey^6-11 revealed that there were few methods reported for the estimation of Lansoprazole and Aspirin by RP-HPLC and UV Spectrophotometry in the combined dosage form. And also HPLC, Spectroscopic methods have been reported for the estimation of individual drugs and in combination with other drugs. Our study, attempts to develop a simple, precise, accurate, sensitive and economical method for the simultaneous estimation of Lansoprazole and Aspirin by UV-Spectrophotometric method in pharmaceutical dosage form.

But administration of low-dose aspirin may cause gastric or duodenal ulcers, thus preventing the onset of ulcers in that patient population is important. Takeda Pharmaceuticals launched Takelda^® combination tablets, a fixed-dose combination (“FDC”) of low-dose aspirin (ASP) with Lansoprazole (LANSO), a proton pump inhibitor⁵. Such a combination is useful for risk reduction of thrombosis and embolism in patients with a history of gastric ulcer or duodenal ulcer, which have had angina, myocardial infarction, coronary artery bypass grafting or percutaneous transluminal coronary angioplasty.

Figure 1: Chemical Structure of Aspirin

Figure 2: Chemical Structure of Lansoprazole

EXPERIMENTAL:

Instrumentation

Double beem UV Visible - Spectrophotometer, Systronics with a pair of 1cm matched quartz cells, All weighing was done on Shimadzu Electric balance, capacity (220gm), readability(0.001gm) and sonication was done in Digital Ultra Sonicator Citizen.

Chemicals and Reagents

Lansoprazole and Aspirin RS were procured from cipla Pharmaceuticals, Hyderabad. Marketed formulation Takelda (Takeda Pharmaceutical Ltd., Mumbai.), with label claim 15 mg LSP 100 mg asp was purchased from local market of Mumbai. Methanol of analytical grade and double distilled water were used throughout the analysis.

Preparation of Methanol

4gm. of NaOH was added to sufficient quantity of distilled water and finally volume was made up to 1000mL with distilled water to get the concentration of Methanol

Solubility Testing

As 0.2M H₂S0₄was already reported as solvent, a trial was made to get an alternate solvent for estimation of Lansoprazole and Aspirin by using Methanol solution. It has been found that Methanol is more suitable as solvent in terms of both solubility and stability.

Preparation of standard stock solutions

Standard stock solutions of Lansoprazole and Aspirin were prepared by dissolving 100mg of each drug in 100mL of methanol individually to get the concentration of 1000µg/mL.

Preparation of working standard solutions

10mL of each drug solution was taken from the stock solution and diluted to 100mL with Methanol in 100mL volumetric flask to get the concentration of 100µg/mL individually.

Determination of λmax

The working standard dilutions of each drug were scanned from 200nm-400nm to determined the λmax individually. Lansoprazole and Aspirin were showed maximum absorbence at 232nm and 222nm respectively.

Validation Parameters

Linearity Range

Adequate dilutions were made from working standards to get the concentrations of 0.5-2.5 µg/mL for Lansoprazole and Aspirin 2-10 µg/mL using Methanol Absorbance of these solutions were determined at their corresponding λmax. The measured absorbance was plotted against concentrations.

Limit of Detection (LOD) and Limit of Quantification (LOQ)

The detection limit of an individual analytical procedure is the lowest of analyte in a sample which can be detected but not necessarily be quantitated as an exact value. The quantification limit of an analytical procedure is the lowest amount of analyte in a sample which can be quantitatively determined with suitable precision and accuracy. It is used particularly for determination of impurities and/degradation studies. For these LOD and LOQ five sets of linear dilutions were prepared and standard graphs were drawn. From the standard graphs standard deviation of the intercept and mean of the slope were calculate, then LOD and LOQ values were calculated using the following formulas.

LOD = 3.3 S_a/b

LOQ = 10 S_a/b

Precision Studies

System Precision: A fixed concentration of 1.5µg/mL of the each standard drug as mixture from the linearity range was checked for absorbance, then SD and percentage RSD values were calculated.

Method Precision: A fixed concentration in the ratio of 1.5 µg/mL of the marketed formulation from the linearity range was checked for absorbance, then SD and percentage RSD values were calculated.

Assay

Accurately weighed and powered 20 tablets of Takelda, manufactured by Takeda Pharmaceutical Ltd.Mumabai,. It contains 100 mg of Aspirin and 15mg of Lansoprazole in the ratio of 8:1. A weight equivalent to 50mg Aspirin of the powdered tablet was taken and to this added 25mL of Methanol in 50mL standard volumetric flask. Ultrasonication was down for 30min. and kept overnight for dissolving. Again ultrasonication was done filtered using Whattman filter paper grade 1, then volume was made up to the mark with Methanol.

The stock solution prepared above contains both the drugs in the ratio of 1:8. 10 mL From the stock solution was taken in the 100mL volumetric flask and the volume was made up to the mark to get the concentration of 100µg/mL of Aspirin and corresponding concentration of Lansoprazole (working standard).

Amount of Lansoprazole and Aspirin present in the marketed formulation was determined by using the following simultaneous equations.

Recovery Studies (Accuracy)

To ensure the reliability (accuracy) of the method recovery studies were carried out by mixing standard quantity of drug with the pre analyzed sample formulation and the contents were reanalyzed by the proposed method. To perform the recovery studies 3 dilutions were prepared using both standard drug and marketed formulation. The dilutions prepared were having concentrations of the marketed formulation in the ratio of 50:100 &150 (ASP: LNS) was kept fixed and the standard drugs mixture in the ratio of 8:1(ASP:LNS) was added in 50%, 100%, 150% respectively.

RESULTS AND DISCUSSION

Fig.3 : UV Spectrum of ASP for Linearity

Fig.4 : UV Spectrum of LNS for Linearity

Table 1: Absorbance values of Aspirin with Methanol

NO.

Concentration

(µg/mL)

Absorbance

at 232nm

At 222nm

0.511

0.742

0.994

1.168

1.373

0.365

0.453

0.532

0.607

0.670

Fig.5 : Standard curve of TEL at 232nm

Table 2: Absorbance values of Lansoprazole with Methanol

S.NO.

Concentration (µg/mL)

Absorbance

at 222nm

At 232nm

0.058

0.094

0.131

0.172

0.206

0.023

0.035

0.050

0.064

0.079

Table 4 : LOD and LOQ values for Aspirin

S.No.	Conc. (µg/mL)	Absorbance at 232nm
S.No.	Conc. (µg/mL)	Set 1	Set 2	Set 3	Set 4	Set 5
1 2 3 4 5	4 8 12 16 20	0.511 0.742 0.994 1.168 1.391	0.519 0.749 0.959 1.171 1.410	0.521 0.752 0.0.963 1.175 1.376	0.506 0.756 0.967 1.156 1.371	0.515 0.732 0.999 1.165 1.388
Intercept		0.305	0.300	0.317	0.312	0.306
S.D. of Intercept 0.0029
Avg. of Slope 0.0538
LOD 0.177µg/ml ; LOQ 0.539 µg/ml

Table 5 : LOD and LOQ values for Lansoprazole

S.No.	Conc.(µg/mL)	Absorbance at 222nm
S.No.	Conc.(µg/mL)	Set 1	Set 2	Set 3	Set 4	Set 5
1 2 3 4 5	4 8 12 16 20	0.058 0.094 0.131 0.172 0.206	0.062 0.099 0.139 0.182 0.212	0.057 0.093 0.132 0.171 0.205	0.058 0.099 0.132 0.181 0.210	0.063 0.095 0.135 0.175 0.215
Intercept		0.02	0.023	0.020	0.02	0.019
S.D. of Intercept 0.0006324
Avg. of Slope 0.007
LOD 0.298µg/ml LOQ 0.903µg/ml

Table 6 : Absorbance values for the System Precision

S.NO.	Conc. (µg/mL)	Absorbance of ASP and LNS
S.NO.	Conc. (µg/mL)	232nm	222nm
1.	12:1.5	1.008	0.708
2.	12:1.5	1.010	0.695
3.	12:1.5	1.001	0.714
4.	12:1.5	1.012	0.691
5.	12:1.5	1.005	0.710

Table 7: Statistical Report of System Precision for ASP and LNS

S.NO.	Parameter	ASP and LNS
S.NO.	Parameter	232nm	222nm
1.	Mean	1.0072	0.7036
2.	Standard deviation	0.0019235	0.0044721
3.	Percentage Relative Standard deviation	0.19097	0.635

Table 8 : Absorbance values for Method Precision

S.NO.	Conc. (µg/mL)	Absorbance of ASP and LNS
S.NO.	Conc. (µg/mL)	232nm	222nm
1.	8:1	0.701	0.480
2.	8:1	0.714	0.489
3.	8:1	0.694	0.485
4.	8:1	0.725	0.475
5.	8:1	0.705	0.487

Table 9 : Statistical Report of Method Precision for ASP and LNS

S.NO.	Parameter	ASP and LNS
S.NO.	Parameter	232nm	222nm
1.	Mean	0.708	0.4832
2.	Standard deviation	0.0052535	0.0025298
3.	Percentage Relative Standard deviation	0.74201	0.523

Table 10 : Intraday Precision values for ASP and LNS at 232nm

S.NO.	Conc.(µg/mL)	ABS at 232nm
S.NO.	Conc.(µg/mL)	S1	S2		S3	S4	S5
1.	4:4	0.397		0.391	0.393	0.389	0.385
2.	8:8	0.724		0.729	0.725	0.719	0.726
3.	12:12	0.976		0.971	0.985	0.980	0.975

Table 16 : Assay Results for the Marketed Formulation

S.NO.	Conc. (µg/mL) ASP:LNS	ABS at (nm)		Amount estimated(µg/mL)		% Purity(w/w)
S.NO.	Conc. (µg/mL) ASP:LNS	232	222	232	222	232	222
1.	8:1	0.742	0.449	8.285	1.040	103.5	104
2.	12:1.5	1.125	0.680	12.5	1.4935	104.5	99.5
3.	16:2	1.365	0.827	15.235	2.02	95.22	101.3

Fig.10: Accuracy Spectrum of Lansoprazole and Aspirin

Table 17: Accuracy Results for Aspirin

S.NO.	Amount of ASP in mrkd. Form. (µg/mL)	Amount of Std LNS added(µg/mL)	Total amount of ASP (µg/mL)	Absorbance	Total amount of ASP found (µg/mL)	%Recovery
1	4	2(50%)	6	0.557	6.219	105
2	4	4(100%)	8	0.741	8.27	105
3	4	6(150%)	10	0.882	9.846	96.1

Table 18 : Accuracy Results for Lansoprazole

S.NO.	Amount of ASP in mrkd. Form. (µg/mL)	Amount of Std. added (µg/mL)	Total amount of LNS (µg/mL)	ABS.	Total amount of ASP found (µg/mL)	%Recovery
1	0.5	0.25(50%)	0.75	0.337	0.775	105
2	0.5	0.5(100%)	1	0.448	0.995	99.12
3	0.5	0.75(150%)	1.25	0.534	1.268	103

Table 19 : Validation results for UV Method (Lansoprazole and Aspirin)

S.NO.	Parameters	Aspirin		Lansoprazole	Acceptance Criteria
1.	Linearity	R ²= 0.996		R²= 0.999	Correlation coefficient (R²= 0.996-0.999)
2.	Precision	System	%RSD = 0.19097	%RSD = 0.635	RSD<2%
		Method	%RSD = 0.74201	%RSD = 0.523
		Intra day	%RSD = 0.222-0.5115	%RSD = 0.23664-0.6473
		Inter day	%RSD = 0.1874-0.444	%RSD = 0.341-0.557
3.	Assay	95.22-103.5%		99.5-104	95-105%
4.	Accuracy	96.1-105%		99.12-105%	95-105%
5.	LOD	0.177µg/mL		0.2981µg/mL	-
6.	LOQ	0.539µg/mL		0.9034µg/mL	-

ABSTRACT: