INTRODUCTION:

Risperidone is a prescription medicine known as an atypical antipsychotic (Figure 1). Chemically it is a 4-[2-[4-(6-fluorobenzo[d]isoxazol-3-yl)-1-piperidyl] ethyl]-3-methyl- 2, 6-diazabicyclo [4.4.0] deca-1, 3-dien-5-one. It is mainly used to treat schizophrenia. It is a dopamine antagonist possessing antiserotonergic, antiadrenergic and antihistaminergic properties^[1]. Risperidone works by blocking the receptors in the brain that dopamine acts on. This prevents the excessive activity of dopamine and helps to control schizophrenia^[2].

The review of literature revealed that HPLC^[3-8] and UV^[9] methods have been reported for estimation of Risperidone in pharmaceutical dosage forms and we here in report a simple and reliable RP- HPLC method for estimation of Risperidone in tablet dosage forms.

Figure 1: Structure of Risperidone

MATERIALS AND METHODS:

Chemicals and Reagents:

Risperidone was kindly provided by Chandra labs, Hyderabad. Risperidone tablets (4mg) from local drug store. Acetonitrile and water of HPLC grade. Potassium dihydrogen phosphate of AR grade was purchased.

Instrument:

An isocratic HPLC system (Shimadzu) equipped with Spinchrome software using RP - C₁₈ Thermo (250mm x 4.6mm, 5µm particle size) using UV detector at 254nm.

Chromatographic conditions:

A mixture of acetonitrile and 0.2M potassium dihydrogen phosphate buffer and (80:20v/v) was used as mobile phase. It was filtered through 0.45µ membrane filter and sonicated prior to use and delivered at a flow rate of 0.7ml/min with injection volume of 20µl. Detection was carried out at 254nm at ambient temperature. The total run time was set at 10min. (Table 1)

Table No.1: Optimized chromatographic conditions:

Parameter	Risperidone
Mobile phase	ACN: 0.2M Potassium dihydrogen phosphate (80:20v/v)
Stationary phase	RP C₁₈ thermo (250mm x 4.6mm, 5µ particle size)
Wave length	254nm
Runtime	10min
Flow rate	0.7ml/min
Injection volume	20µl
Temperature	Ambient
Mode of operation	Isocratic

Preparation of buffer (0.2M):

Accurately weighed 27.218g of Potassium dihydrogen phosphate and dissolved in 1Lit of HPLC grade water

Preparation of mobile phase:

Buffer and acetonitrile in the ratio of 20:80v/v was employed as a mobile phase.

Preparation of standard stock solution:

100mg of pure Risperidone was accurately weighed and transferred to 100ml volumetric flask and dissolved in 60ml mobile phase. The flask was sonicated for 10min and the volume made to the mark with mobile phase. Appropriate volume of aliquot from Risperidone standard stock solution was further diluted with mobile phase to obtain the concentration 100µg/ml. This solution was further diluted to obtain concentrations in the range of 2-10µg/ml. (Fig 2)

Fig No.2 Typical chromatogram of Risperidone

Analysis of formulation:

Not less than 20 tablets each claimed to 4mg of Risperidone were weighed and powdered. The weighed portion of the tablet powder must be equivalent to 50mg was taken in 50ml volumetric flask. 30ml of mobile phase was added to same volumetric flask and sonicated for 10min and then diluted up to the mark with same mobile phase. The resulting solution was filtered through 0.45µ membrane filter. Appropriate volume of aliquot from above solution was further diluted with mobile phase to obtain the concentration of 100µg/ml and further diluted to obtain the concentration of 10µg/ml. The resulting solution was injected (20µl) 6 times in to the column to obtain chromatogram. (Table 2)

Table No. 2: Analysis of formulation

Brand name

Drug

Amount labelled (mg)

Amount found(mg)

Recovery

Risperdal

Risperidone

3.98

99.5

Method validation:

The proposed method has been validated in terms of Specificity, System suitability, Linearity, Precision, Accuracy, LOD and LOQ.

Specificity:

The specificity test of the proposed method demonstrated that the Excipients from tablets do not interfere in the drug peak. So the proposed method was specified.

System suitability:

Suitability of the chromatographic system was tested before each stage of validation. System suitability tests were carried out on freshly prepared standard solution to check the parameters (Retention time, No. of theoretical plates and Asymmetry). (Table 3)

Table No.3: System suitability parameters

Parameters	Results
Retention time	5.683min
Area	2418.2
Theoretical plates	3542
Tailing factor	0.9

Linearity:

The linearity of this method was determined at five different concentration levels ranging from 2-10µg/ml. The standard solutions were chromatographed using above chromatographic conditions. Calibration curve was constructed by plotting average peak area Vs concentration. The regression equation and correlation coefficient (r²) were found to be Y=29.051x+54.58 and 0.9982 respectively. (Fig 3, Table 3)

Fig 3 Calibration curve of Risperidone

Table No.3: Linearity data

Concentration (µg/ml)	Peak area (mU)
0	0
2	644.225
4	1195.28
6	1840.383
8	2322.61
10	2985.638

Precision:

It is a measure of the ability of the method to generate reproducible results. The intra day and interday precision study of Risperidone was carried out at the concentration of 8µg/ml. (Table 4)

Table No.4: Validation parameters for proposed method

Parameters	Results
Linearity(µg/ml)	2-10
Slope	29.05
Intercept	54.58
Correlation coefficient(r²)	0.9982
Regression equation(Y=mx+C)	Y=29.051x+54.58
Method precision(%RSD) Intraday Interday	0.092 0.095
%Recovery	99.7-100.3
LOD(µg/ml)	0.25
LOQ(µg/ml)	0.75

Accuracy and recovery:

Accuracy was determined at three different concentration levels 80%, 100% and 120% by adding pure drug to the sample. The results were showed in Table 5.

Table No. 5: Recovery Data

Drug name

Levels

Amount added

(mg)

Amount recovered

(mg)

% Recovery

Risperidone

80%

100%

120%

3.2

4.8

3.21

3.99

4.81

100.3

99.75

100.2

RESULTS AND DISCUSSION:

The aim of this study was to develop a simple, accurate and precise HPLC method or the analysis of Risperidone in tablet dosage forms. The retention was found to be 5.6min. This indicates the present method was rapid and economical. The asymmetric factor for Risperidone was 0.9. Summary of validation parameters for proposed method was given in Table 5. From the calibration curve r² was found to be within the limits i.e., 0.9982. The recovery was found to be in the range of 99.7-100.3%. The precision o the proposed method was determined by intraday and interday variation and was expressed as the %RSD (0.092 and 0.095). The LOD and LOQ were found to be 0.25 µg/ml and 0.75µg/ml respectively.

CONCLUSION:

From the above discussion the validated RP-HPLC method for Risperidone was found to be simple, sensitive, precise, accurate and economical. Hence this method can be used for routine determination of Risperidone in pure sample and tablet dosage forms.

REFERENCES:

1. http://en.wikipedia.org/wiki/Risperidone.

2. http://www.netdoctor.co.uk/brain-and-nervous-system/medicines/ risperdal.html.

3. Dhara Patel, Jayvadan Patel. Development and validation of RP-HPLC method for simultaneous estimation of Risperidone and trihexyphenidyl hydrochloride in tablet dosage forms. International Journal of Pharmaceutical Sciences Review and Research. 4(3); 2010:85-88.

4. Suthar A P, Dubey S A, Patel S R, Shah A M. Determination of Risperidone and forced degradation Behavior by HPLC in tablet dosage form. International Journal of PharmTech Research. 1(3); 2009:568-574

5. Dharmaraj Santhosam S, Kannan S. An HPLC method for the Simultaneous Estimation of Risperidone and Trihexyphenidyl hydrochloride from Bulk and Dosage forms. Hygeia.J.D.Med. 3 (1); 2011:29- 33.

6. Bujji Babu N, Ramesh Raju R. Simultaneous analysis and Validation of Risperidone and Drospirenone Drugs in Pharmaceutical dosage form. International Journal of Research in Pharmaceutical and Biomedical Sciences. 2(4); 2011:1638-42.

7. Manikandan K, Lakshmi K S. Method development and validation of risperidone by RP-HPLC. International Journal of Research in Pharmaceutical and Nano Sciences. 1(1); 2012:87-95.

8. Baldania S L, Bhatt K K, Mehta R S, Shah D A. RP-HPLC Estimation of Risperidone in Tablet Dosage Forms. Indian Journal of Pharmaceutical Sciences. 70(4);2008 494–497.

9. Sravan Kumar M, Anton Smith A, Alagumani Vasagam G, Kottai Muthu A Manavalan R. Development of Analytical Method for Risperidone by UV Spectrophotometry. International Journal of Pharma Sciences and Research. 1(2); 2010:122-126.

Received on 26.03.2013 Modified on 15.04.2013

Research J. Pharm. and Tech 6(6): June 2013; Page 659-661