1.0 INTRODUCTION:

Aripiprazole (APZ) (Fig.1) is an atypical antipsychotic agent belonging to the chemical class of benzisoxazole derivatives and is indicated for the treatment of schizophrenia. Aripiprazole is a selective monoaminergic antagonist with high affinity for the serotonin Type 2 (5HT2), dopamine Type 2 (D2), 1 and 2 adrenergic, and H1 histaminergic receptors. Aripiprazole appears to mediate its antipsychotic effects primarily by partial agonism at the D2 receptor. In addition to partial agonist activity at the D2 receptor, Aripiprazole is also a partial agonist at the 5-HT1A receptor, and like the other atypical antipsychotics, Aripiprazole displays an antagonist profile at the 5-HT2A receptor. Aripiprazole has moderate affinity for histamine and alpha adrenergic receptors, and no appreciable affinity for cholinergic muscarinic receptors ^1-2.

A thorough literature survey has revealed very few methods for the estimation of aripiprazole using spectrophotometric technique ^3-6. Methods reported are simple hence need arises to develop a rapid, economical, precise and accurate method for estimation of Aripiprazole in tablet formulations.

2.0 EXPERIMENTAL:

2.1 Chemicals and Reagents:

All the reagents were of analytical grade unless stated otherwise. Phosphoric acid and Acetonitrile (Merck, Mumbai, India) were used. Aripiprazole Standard was obtained as a gift sample from Hetero Drugs Ltd, Hyderabad, India and Aripiprazole tablets were purchased from Local Pharmacy.

2.2 Instrumentation:

Shimadzu UV 1700, UV/Vis double beam spectrophotometer with spectral band width of 1 nm, wavelength accuracy of ± 0.3 nm and 1.0 cm matched quartz cells was used for analytical method development.

2.3 Media Preparation:

0.05M Phosphoric acid in water and Acetonitrile were mixed in the ratio of 40:60 v/v.

2.4 Mobile phase:

A filtered and degassed mixture of acetonitrile and 0.05 M phosphate buffer, pH 3.2 in the ratio of 35:65 v/v was used.

2.5 Standard Preparation:

Standard stock solution was prepared by dissolving 25 mg of Aripiprazole working standard in 25 mL of Media. From the above stock solution, a series of solutions were prepared at concentration levels ranging from 2.5µg mL^-1 to 20 µg/mL, measured the responses of solutions at all levels in triplicate.

2.6 Sample solution:

20 tablets were accurately weighed and grounded to fine powder. Aripiprazole tablet powder equivalent to the label claim was accurately weighed and transferred into a 100 mL volumetric flask, few mL of Media was added and sonicated to dissolve and made up the volume with Media. The above solution was filtered and diluted to get a final concentration of 10 µg mL^-1.

2.7 Method Validation:

The developed was validated as per published guidelines with respect to accuracy, precision, linearity, ruggedness, sensitivity and stability.

3.0. RESULTS AND DISCUSSION:

The Spectrum of the Aripiprazole depicted occurrence of two maximas at 218 nm and 251 nm. The spectra of standard and sample were shown in Fig 1.

Fig.1. Chemical Structure of Aripiprazole

Fig 1: A. UV spectrum of Aripiprazole in 0.05M phosphoric acid: ACN (40:60)-Standard

B. UV spectrum of Aripiprazole in 0.05M phosphoric acid: ACN (40:60)-Sample

Table 1: Molar absorptivities of Aripiprazole

Preparation No	Molar absorptivities		Mean Molar absorptivities
Preparation No	at 218nm	at 251nm	at 218nm	at 251nm
1	44350	10806	44346.8+0.02%	10806.8+0.05%
2	44341	10802
3	44345	10811
4	44337	10805
5	44349	10801
6	44359	10816

Sensitivity:

The limit of detection (LOD) and was calculated using the following equation LOD=3.3σ/s Where σ is standard deviation of y intercept of calibration curve (n=6) and s is slope of Regression equation. Sandell’s sensitivity for Aripiprazole was 0.01011 μg.cm2/0.001 abs respectively (Table 2).

Table 2: Optical characteristics of Aripiprazole

Parameters	Values
λ max nm	218nm
Beer’s law limit, µg mL^-1	2-20
Sandell’s sensitivity, μg cm^-2/0.001 absorbance unit	0.01011
Molar absorptivity, L moL^-1 cm^-1	2.2 x 10⁵
Regression equation (Y = bx + c)**	0.0826x +0.1334
Slope(b)	0.08026
Intercept(c)	0.1334
Correlation coefficient (r²)	0.9992
% Relative Standard Deviation (R.S.D)*	0.02
% Range of error (Confidence)*
At 0.05 Level	0.34
At 0.01 level	0.44
Limit of Detection (μg / ml)	0.01
Limit of Quantification (μg /ml)	0.1
Stability (h.)	1 month

**Y = bX+c, where Y is the absorbance and X is the concentration of drug in μg /mL; *Average of six determinations.

Calculating formulas used

01. Molar Absorptivity, ε = A / c l

(Where A= absorbance, c = sample concentration in moles/liter & l = length of light path through the sample in cm.)

02. Sandell’s Sensitivity = Molecular weight / Molar Absorptivity

03. Regression equation Y = bX+c, where Y is the absorbance and X is the concentration of drug in μg /ml

04. Limit of Detection (μg / ml) = 3.3σ/s

05. Limit of Quantification (μg /ml) = 10σ/s

Where σ is Standard deviation

Precision:

The precision of the method was established by carrying out the analysis of the analytes (n=6) using the proposed developed methods. The low value of standard deviation showed that the methods were precise (Table 3).

Table 3: System Precision results for Aripiprazole

Standard Preparations	Absorbance	Absorptivities
Preparation-1	0.9889	98.89
Preparation-2	0.9889	98.89
Preparation-3	0.9884	98.84
Preparation-4	0.9888	98.88
Preparation-5	0.9886	98.86
Preparation-6	0.9885	98.85
Average	0.9887	98.87
Std Dev	0.00	0.02
% RSD	0.02	0.02

Ruggedness:

The ruggedness test of analytical assay method is defined as degree of reproducibility of assay results obtained by the successful applications of assay over different time, day and among multiple analysts. In this study, the proposed method for determination of Aripiprazole were Carried out at different time interval, day and two analysts (Table 4).

Table 4: Ruggedness results for Aripiprazole

Preparations	Inter day % of Assay	Intraday % of Assay
Preparation-1	99.8	99.9
Preparation-2	99.9	100
Preparation-3	99.9	100.2
Preparation-4	99.8	99.8
Preparation-5	100.1	99.7
Preparation-6	100.4	100.2
Average	99.98	99.97
Std Dev	0.23	0.21
% RSD	0.23	0.21

Accuracy:

To check the accuracy of the developed methods and to study the interference of formulation excipients, analytical recovery experiments were carried out by using standard addition method at 50, 100, 150% levels. From the total amount of drug found, the percentage recovery was calculated. The results revealed no interference of excipients. The recovery of Aripiprazole from the Assay Preparations was found to be 99.97 % and 100.4% respectively (Table 5). The recovery results indicated that the method is accurate, reproducible and Aripiprazole could be quantified by this procedure simultaneously.

Table 5: recovery studies of Aripiprazole

% Spiked to the label amount	Amount added (mg)	Amount found (mg)	% Recovery	Mean % Recovery
% Spiked to the label amount	Amount added (mg)	Amount found (mg)	% Recovery	N=3,+SEM
50% - 1	15.01	15.01	100.00	100.00+0.01
50% - 2	15.04	15.03	99.93
50% - 3	15.02	15.03	100.07
100% - 1	30.03	30.02	100.03	100.00+0.02
100% - 2	30.01	30.04	99.9
100% - 3	30.03	30.01	100.07
150% - 1	45.01	45.02	99.97	99.95+0.01
150% - 2	45.02	45.03	99.97
150% - 3	45.01	45.04	99.92

Linearity:

In the developed Spectrophotometric method, Aripiprazole showed linearity with absorbance in the range 2-20 μg mL^-1 at their respective maxima, which were validated by least square method. (Fig 2&3).

Fig 2: Plot of Linearity for Aripiprazole

Fig 3: Overlay spectrum for Aripiprazole (2.5-20 µg mL^-1)

Stability:

The standard stock solutions of Aripiprazole were stored, in two different conditions, at ±50C and at ambient temperature for one month. During this period, the solutions were analyzed with UV spectrophotometric method, the spectrum was compared with the spectrum of daily prepared standard solution, and no difference was obtained between them. It is decided that Aripiprazole is highly stable in the mentioned conditions (Table2).

4.0 CONCLUSION:

The developed method was found to be rapid, precise, accurate and sensitive. The statistical parameters and recovery study data clearly indicate the reproducibility and accuracy of this method. Analysis of the authentic sample containing aripiprazole showed no interference from the common excipients. Hence, the method could be considered for the routine estimation of aripiprazole in tablets.

5.0 REFERENCES:

1. http://www.rxlist.com/abilify-drug.htm

2. http://www.accessdata.fda.gov/drugsatfda_docs/label/2010/02143 6s031,021866s018,021713s023,021729s016lbl. pdf

3. R. Kalaichelvi, B. Thangabalan, D. Srinivasa rao and E. Jayachandran, UV Spectrophotometric Determination of Aripiprazole in Bulk and Pharmaceutical Formulation. E-Journal of Chemistry. 6(S1); 2009:S87-S90.

4. Attri Nandini and Yadav Sachdev, Spectrophotometric determination of aripiprazole in tablet formulation. The Indian Pharmacist. 8(88); 2009:69-71.

5. Samiran Dey , Nitesh Chauhan ,Dr. P. Malairajan, R. Murugan , Rakhal Chandra Das and Shafique Ahmad. A Simple and Rapid Spectrophotometric Determination of Aripiprazole in Pharmaceutical Dosage Form. International Journal of Drug Development & Research. 3(1); 2011:205-208.

6. H.S.Patle, A.V.Chandewar and M.D.Kshirsagar, Development and validation of UV spectrophotometric determination of aripiprazole in bulk and tablet formulation. Int. J. Curr Pharm Res. 3(3); 2011: 59-61.

Received on 09.07.2011 Accepted on 12.08.2011

Asian J. Pharm. Ana. 1(3): July-Sept. 2011; Page 46-49