Stability Indicating Simultaneous Equation 1 Method for Determination of Domperidone and 2 ( S )-Esomeprazole Magnesium in Capsule 3 Dosage Form Using UV-Spectrophotometer

9 Department of Pharmaceutical Chemistry, Invertis Institute of Pharmacy, Invertis University, 10 Bareilly-243 123, Uttar Pradesh, India 11 Department of Pharmacology, Invertis Institute of Pharmacy, Invertis University, Bareilly-243 12 123, Uttar Pradesh, India 13 Department of Pharmacognosy, Invertis Institute of Pharmacy, Invertis University, Bareilly14 243 123, Uttar Pradesh, India 15 Department of Pharmaceutics, Invertis Institute of Pharmacy, Invertis University, Bareilly16 243 123, Uttar Pradesh, India 17

(S)-Esomeprazole Magnesium (EOZ) (Fig. 1) is chemically bis(5-methoxy-2-[(S)-[(4methoxy-3,5-dimethyl-2pyridinyl)methyl]sulfinyl]-1-H-enzimidazole-1-yl), a compound that inhibits gastric acid secretion (Scott et al. 2002).(S)-Esomeprazole Magnesium is cost effective in the treatment of gastric oesophageal reflux diseases.It is S-isomer of omeprazole and is the first single optical isomer proton pump inhibitor.It provides better acid control than current racemic proton pump inhibitors and has a favourable pharmacokinetic profile relative to omeprazole (Sean C et al. 2002).Domperidone (DOMPE) (Fig. 1), a dopamine antagonist is usually given along with proton pump inhibitors as ulcers are usually attended with vomiting.Chemically, it is [5-chloro-1-[1,3-(2,3-dihydro-2-oxo-1Hbenzmidazole-1yl)propyl)-4-piperdinyl-1,3-dihydro-2H-benzimidazole-2-one] (The Merck Index 2001).The stability-indicating assay is a method that is employed for the analysis of stability samples in pharmaceutical industry (Bakshi et al. 2002).Stability testing plays an important role in the process of drug development.The purpose of stability testing is to provide confirmation on how quality of a drug substance varies with time under the influence of a variety of environmental factors such as temperature, humidity, and light and enables recommendation of storage conditions, and shelf life to be established (Mahajan et al. 2012).
The method is expected to allow analysis of individual degradation products (Bakshi et al. 2002).

Apparatus
A UV-Visible spectrophotometer, model UV-3200 (Labindia) with 1cm quartz cells.An electronic balance (Roy electronics-LCBCN5) was used for weighing the samples.Hot Air Oven (Coslab CLE-101) was used for the thermal degradation study.A Sonicator (Labfit) was also used.

Standard Stock Solution
Standard stock solution (1000 µg/ml) of esomeprazole and domperidone were prepared by dissolving accurately about 50 mg of each drug separately in methanol in 50 ml volumetric flask.The working solution was in the range of 1-6 µg/ ml for esomeprazole and 5-30 µg/ ml for domperidone were prepared by further dilution for calibration curves.
Zero order overlain spectra (Fig. 2) were carried out at 299 nm and 287 nm, the maximum absorbance wavelength of esomeprazole magnesium and domperidone respectively.Appropriate dilution were prepared using methanol from the stock solution 1000 µg/ ml of esomeprazole magnesium and domperidone to get aliquots of the concentration of 1-6 µg/ ml and 30 µg/ ml for esomeprazole and domperidone respectively.The calibration curve (Fig. 3) was plotted from mean absorbance values of observation of the six replicate.The absorptivity values for both the drug were determined at their respective λmax by measuring absorbance values for working standard of esomeprazole magnesium and domperidone.
The concentration of esomeprazole magnesium and domperidone were determined by solving the following equation (Beckett AH et al. 1997) Where Cx and Cy are the concentration of esomeprazole and domperidone respectively.

Recovery studies
To study the accuracy of the proposed methods, recovery studies were carried out by standard addition method at three different levels (80%, 100% and 120% of the test concentration as per ICH guidelines).A known amount of drug was added to pre analyzed * Tel.: +918859120888.E-mail address: rssunil29@rediffmail.com; sunil.s@invertis.org.capsule powder and percentage recoveries were calculated.The result of recovery studies was satisfactory.

Linearity and range
The six point calibration curve that were constructed were linear over the concentration range between 1-6 µg/ml for esomeprazole and 5-30 µg/ml for domperidone respectively.
Each concentration was repeated for 3 times.

Precision
For evaluation of intraday precision repeatability of the result was evaluated for the concentration of 1 µg/ml for esomeprazole and 15 µg/ml for domperidone by 3 replicate determination at interval of 1 hour and for evaluation of interday precision repeatability of the result was evaluated for the concentration of 1 µg/ml for esomeprazole and 15 µg/ml for domperidone by 3 replicate determination at interval of 1 hour for 3 days.

Limit of detection
Limit of detection for esomeprazole was found to be 0.116 and for domperidone was found to be 0.657.

Limit of quantification
Limit of quantification for esomeprazole and domperidone was found to de 0.386 and 2.18 respectively.

Robustness
Robustness of proposed method was performed by changing the UV analyst and remaining condition was keeping constant.

Stability Indicating Assay Method 2.5.1 Acid degradation
In the 1 µg/ml solution of esomeprazole magnesium and 15 µg/ml solution of domperidone 10 ml 1N HCl were added and kept at room temperature for 24 hours.

Base degradation
In the 1µg/ml solution of esomeprazole magnesium and 15µg/ml solution of domperidone 10 ml 1N NaOH were added and kept at room temperature for 24 hours.

Thermal degradation
About 50 mg of drug substance kept at 60ºC for 8 hours.Then the solution was prepared to achieve 1µg/ml for esomeprazole magnesium and 15 µg/ml for domperidone respectively.

Photolytic degradation
About 50 mg of drug substance kept direct to the sun light for 12 hours.Then the solution was prepared to achieve 1µg/ml for esomeprazole magnesium and 15 µg/ml for domperidone respectively.* Tel.: +918859120888.E-mail address: rssunil29@rediffmail.com; sunil.s@invertis.org.

Statistical analyses
Means, standard deviation (SD), relative standard deviation (RSD) and linear regression analysis were calculated using Microsoft Excel 2007.

RESULT AND DISCUSSION
Many pharmaceutical compounds undergo degradation during storage or even during the different processes of their manufacture.Several chemical or physical factors can lead to the degradation of drugs (Henry MB et al.1963).Hydrolysis and oxidation are the most famous chemical degradation routes of drugs (Florence AT et al. 1998& Banker GS et al. 2002).
The main classes of drugs that are subject to degradation are esters, amides and lactams.
Ester hydrolysis is frequently base catalysed, which makes the reaction rapid, and irreversible (Florence AT et al. 1998& James IW 1988).
In UV-Spectroscopic method, the crossing points of spectra were utilized for developing the equation for simultaneous analysis and analytical data are present in Table 1 In the method, wavelengths were utilized 299 nm for esomeprazole magnesium and 287 nm for domperidone.The percentage recovery value obtained was within standard limit of 98% to101% for the method which confirmed that the method was accurate and free from any interference of excipients.The low value of standard deviation obtained confirmed precision of the method.The reproducibility, repeatability and accuracy of the proposed method were found to be satisfactory, limit of detection and limit of quantitation was calculated, the result was satisfactory.All recovery studies were compiled in Table 2.

Esomeprazole magnesium Domperidone
Linearity range 1-6µg/ ml 5-30 µg/ ml * Tel.: +918859120888.E-mail address: rssunil29@rediffmail.com; sunil.s@invertis.org.* Tel.: +918859120888.E-mail address: rssunil29@rediffmail.com; sunil.s@invertis.org.all parameters was found to be less than one, which indicate that the validity of method are also within the limit so the proposed method can be used for routine quantative simultaneous estimation of both the drug.

Fig. 1
Fig. 1 Chemical structure of esomeprazole and domperidone

Fig. 6 :
Fig. 6: Thermal degradation of esomeprazole and domperidonePhotolytic degradation was performed in combination, the drugs produced degradates and showed the parent peak at 287, 231, 210 nm for domperidone and 299, 209, 204 nm for esomeprazole magnesium.Fig.7

Table 1 . Analysis of commercial formulation in capsule dosage form
.