New Simple, Sensitive and Economical UV Spectrophotometric Method for Estimation of Risperidone in Tablet Dosage Form and its Peroxide Degradation Kinetic

Ashok P Suthar¹*, Sanjay R Patel¹, Anand M Shah¹, Roshan Issarani², BP Nagori² and Rumit M Shah³

¹Dept. of Pharmaceutical Analysis, KNV Pharmacy College, Metoda-360021, Rajkot, India.

²Dept. of Quality Assurance, Lachoo Memorial College of Science and Technology, Shastrinagar-342003, Jodhpur, India.

³Vidyabharati Trust College of Pharmacy, Umarakh, Surat, India.

ABSTRACT

New simple, economic, sensitive, accurate UV Spectrophotometric method has been developed for determination of Risperidone in tablet dosage form. Method of estimation for Risperidone based on two wavelengths viz. 238 nm and 276 nm, by solvent mixture of 0.1N HCl: Methanol in the proportion of 30:70. Risperidone shows linearity and obeys Beer’s law in the concentration range of 3 to 27µg ml^-1 at both wavelengths. The results of analysis are validated by statistical evaluation and recovery studies, and method can be extended to the analysis of Risperidone in tablet formulations. A kinetic investigation of the peroxide hydrolysis of Risperidone was carried out in 1% and 3% Hydrogen peroxide solution. The rate constant for degradation were estimated as per pseudo-first order kinetic.

Keywords: Risperidone, UV Spectrophotometric method, λ_max, Degradation kinetic

INTRODUCTION:

Risperidone (RISP) is belonging to the chemical class of benzisoxazole derivatives and chemically, it is 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 with molecular formula C₂₃H₂₇FN₄O₂ and CAS number 106266-06-2¹. Risperidone is official in BP 2007². Risperidone is atypical psychotropic agent and used as an antipsychotic for bipolar disorder, borderline personality disorder, drug intoxication, brief drug-induced psychosis, and other schizophreniform and psychiatric disorder. Risperidone is mostly metabolized by alicyclic hydroxylation and oxidative N-dealkylation³.

Literature review for Risperidone analysis revealed several methods based on different technique such as; Visible spectrophotometric methods⁴, LC-MS and HPLC-ESI/MS assay for its quantification in plasma and serum^5-8, Chiral chromatography⁹, Pulse polarography¹⁰, Chemiluminescence assay¹¹, LC with Coulometric detection¹². However, there is no method reported for quantification of RISP in tablet dosage forms in the literature.

Stress testing forms an important part of the API and drug product development. The purpose of stress testing is to provide evidence on how the quality of drug substance varies with time under the effect of varieties of environmental factors such as temperature, humidity, light and presence of oxygen¹³. The study of drug degradation kinetics is of greater importance for development of stable formulation and establishment of expiration date for commercially available drug products in laboratories of pharmaceutical industries. The degradation rate kinetic gives the information regarding the rate of process that generally lead to the

Table1: Optical parameters and regression characteristics for risperidone

Parameters	238 nm^a	276 nm^a
Beer’s law limit (mg/ml)	3-27	3-27
Molar absorptivity (l mole^-1cm^-1)	1.505 x 10^4	0.871 x 10^4
Sandell's sensitivity (mg/cm^2/0.001absorbance unit)	0.027	0.047
Regression equation (y= mx+c) Slope (m) Intercept (c)	0.036 0.008	0.021 0.005
Correlation coefficient (r^2)	0.999	0.999

^aMean of triplicate determination

Fig. 1: Scan of standard solution of Risperidone (100 µg/ml)

inactivation of drug through either decomposition or loss of drug by conversion to a less favorable physical or chemical form^{14, 15}.

The aim of present work is to develop a feasible, accurate, economic analytical procedure for the analysis of Risperidone in tablet dosage form. Moreover, kinetic studies and accelerated stability experiments to predict expiry dates of pharmaceutical products necessitate such methods.

MATERIAL AND METHODS:

Reagent and Materials:

Risperidone Working Standard was supplied by Torrent Pharmaceutical Ltd. and sample tablet (Label claim: 1 mg and 4 mg; Respidon tablet; and manufacturer: Torrent Pharmaceutical Ltd.) were procured from the market. Methanol, Conc. HCl, Hydrogen Peroxide (all AR grade) and Distilled water (Milli-pore) were used.

Apparatus:

An UV/Vis double beam spectrophotometer of make Shimadzu, UV-2450 with spectral bandwidth 2 nm and wavelength accuracy 0.3 nm, and 1 cm matched quartz cell, Sartorius weighing balance, CP225D and PEI make ultra-sonicator were used for experimental purpose.

Methods:

Diluent preparation:

Solvent mixture of 0.1N HCl and methanol, in the ratio of 30:70 was used as diluent that selected by performing solubility study.

Stock Solution:

A stock solution of RISP containing 1 mg ml^-1 was prepared by dissolving pure 100 mg RISP working standard in 100 ml diluent.

Table 2: Validation parameters for Risperidone

Parameters	238 nm	276 nm
Linearity Range (mg/ml)	3-27	3-27
Precision (% RSD)
Repeatability (n=6)	0.497	0.384
Intraday (n=3)	0.131 – 1.001	0.204 - 1.327
Interday (n=3)	0.275 – 0.997	0.269 – 1.477
Accuracy (%)	98.87 – 101.85	98.32 – 101.70
Specificity	Specific	Specific

Fig. 2 a: Linearity curve of Risperidone at 238 nm

b: Linearity curve of Risperidone at 276 nm

Standard Solution:

From stock solutions, 1.5 mL of Risperidone solution were transferred to a 100 mL clean volumetric flask and the volume was made up with diluent and mix well.

Determination of wavelength maxima:

A standard solution of Risperidone containing 100 µg mL^-1 was prepared from stock solution and scanned in the wavelength range of 200-400 nm.

Sample preparation:

Twenty tablets were weighed accurately; the average weight was determined and then ground to a fine powder. A quantity equivalent to 15 mg of RISP was transferred to 100 ml volumetric flask. 70 ml of diluent was added to the same flask and sonicated for 30 min. The volume was made up to the mark with diluent and solution was filtered through 0.2 µm glass nylon filter. From the filtrate, suitable aliquot was withdrawn diluted to obtain 20 µg ml^-1 of RISP. The sample was measured at both wavelengths.

Validation of method:

Validation of the developed method was done according to ICH Q2 (R1), 2005 guideline ¹⁶.

Degradation kinetic study:

Proposed method was extended to kinetic study of risperidone for identifying degradation behavior. Risperidone was allowed to hydrolyze in different condition viz. different pH, thermal, oxidation but satisfactory degradation was found to be in oxidation condition.

Fig. 3: Effect of concentration of H₂O₂ on degradation of risperidone

Hydrogen peroxide-induced degradation:

Suitable aliquots of Risperidone stock solution were transferred to series of three 50 ml volumetric. To it, 35 ml of diluent was added to the same flask; 0 ml H₂O₂ (control), 4 ml 1% H₂O₂ and 4 ml 3% H₂O₂ was added to such volumetric flask, respectively and mix well. Then, volume was made up to mark with same diluent to set final concentration 15 µg ml^-1. The absorbance was measured at 238 nm only against diluent as solvent blank at 10 minutes intervals at ambient temperature.

RESULTS AND DISCUSSION:

The proposed UV Spectrophotometric method for estimation of Risperidone in tablet dosage form was found to be simple, economical, accurate and rapid.

From the UV spectra of Risperidone between wavelength range of 200-400, two wavelength 238 nm and 276 nm selected for estimation of Risperidone (Fig. 1). At both the wavelengths, drug obeys Beer’s law over the concentration range 3-27µg mL^-1. Optical parameters and regression parameter for Risperidone by proposed UV Spectrophotometric method are presented in Table 1.

Calibration curves:

The linear regression data for calibration curves by proposed method indicate that response is linear over the concentration range of 3-27 µg mL^-1 (Fig. 2 a and b). % RSD is less than 2% at both wavelengths viz. 238 nm and 276 nm. The regression equation was computed and found to be:

y = 0.036x + 0.008, r²=0.999 at 238 nm.

y = 0.021x + 0.005, r²=0.999 at 276 nm

Where, y is absorbance of analyte, x is concentration of the drug in µg ml^-1 and r² is correlation coefficient.

Table 3: Estimation of risperidone in tablet by UV method

lmax	Brand name^b	Label claim (mg)	Mean ± SD (%) (n=3)	% RSD
238	Respidon-1	1	100.01 ± 0.344	0.344
	Respidon-4	4	99.91 ± 0.332	0.332
276	Respidon-1	1	99.30 ± 0.466	0.469
	Respidon-4	4	99.36 ± 0.667	0.671

^bRespidon-1 and Respidon-4 indicates 1 and 4 mg strength, respectively

Table 4: Comparison of results for determination of Risperidone in tablet by UV method

Sr. No.	238 nm	276 nm
1	99.34	98.68
2	98.87	99.21
3	99.87	100.54
4	100.77	99.17
5	101.23	99.82
Mean	100.02	99.48
tStat	1.170
tCritical	2.776

Table 5: Kinetic data for oxidative hydrolysis of Risperidone

Conc. of H2O2	K in min^-1	t1/2 in min
1% H2O2	0.00042	1650.00
3% H2O2	0.00098	707.14

Validation of the method:

Precision:

The precision of analytical method is determined by assaying a sufficient number of aliquots of homogenous sample to be able to calculate statistically valid estimate of % RSD (Relative Standard deviation). Repeatability of a standard sample was carried out using six replicate of same solution (15 µg ml^-1). It showed RSD of 0.497 and 0.384 at 238 nm and 276 nm respectively. This shows method is precise as relative standard deviation is below 2.0%. Intermediate precision of the method was determined by same sample by three different analysts on different time duration. Validation parameters for analysis of Risperidone are presented in Table 2.

Accuracy:

The accuracy of the method was determined by spiking working standard into tablet solution. The recovery studies were performed by standard addition method, at 60%, 100%, 140% level. Percent recovered was calculated by comparing the absorbance before and after the addition of the working standard. For both the wavelengths and strengths, recovery performed in the same way. Recovery of Risperidone in the range of 98.32-101.85% shows method may be used for routine analysis of Risperidone in tablet dosage form. The percent recovery indicates the accuracy of the developed method.

Specificity:

Results of specificity studies shows no interference of excipients.

Analysis of marketed formulations:

The developed method was applied to the analysis of Risperidone in tablet dosage from marketed as Respidon (Label claim 1 and 4 mg strength, Torrent Pharmaceutical Ltd.). The results of analysis are given in Table 3.

The contents of marketed tablet dosage form were found to be in the range of 80-120% with RSD less than 2% which indicate suitability for routine analysis of Risperidone in tablet dosage form.

Statistical analysis/Comparison at both wavelengths:

The results of the determination of RISP in tablet dosage form obtained by proposed method at both wavelengths are compared by applying statistical treatment like 2-tailed student’s t-test. As the calculated t-values are less than the table t-value (i.e. critical), there is no significant difference in the content of Risperidone estimated by the both wavelengths (Table 4).

Fig. 4: Proposed degradation scheme of Risperidone

Kinetics of Degradation:

A preliminary investigation on hydrolytic oxidation of Risperidone was conducted with hydrogen peroxide. Proposed scheme for preparing degradation product presented in Fig. 3. Risperidone and its degradation product Risperidone N-Oxide have the same UV spectrum since conjugation moiety does not change. The dimensionless concentration ratio C_t/C₀ is plotted against time of Risperidone presents in Fig. 4. Here C₀ is the initial concentration in µg mL^-1 and C_t is the concentration remaining at the time‘t’ in min. It is observed that linear degradation was found to be in case of 1% H₂O₂ while in case of 3% H₂O₂; initial degradation was rapid followed by linear degradation. Kinetic data for degradation study presents in Table 5.

CONCLUSION:

The proposed study describes new UV spectrophotometric method for the estimation of risperidone in tablet dosage form. The method was validated and statistical analysis proves that method is simple, sensitive, economical, accurate and precise. Percentage of recovery shows that the method is free from interference of the excipients used in the formulation. In addition, oxidative hydrolysis of Risperidone was found to follow a pseudo-first order reaction rate. The developed method is suitable for the quality control analysis of Risperidone in tablet dosage form.

ACKNOWLEDGEMENT:

The authors are thankful to Prof. B.P. Nagori, Director, Lachoo Memorial College of Science and Technology, Jodhpur, India, for providing research facilities and to Torrent Pharmaceuticals Ltd. Ahmedabad, India, R and D Centre, for the gift sample of Risperidone pure sample.

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Received on 10.07.2009

Accepted on 19.08.2009

© A & V Publication all right reserved

Research Journal of Pharmaceutical Dosage Forms and Technology. 1(2): Sept.-Oct. 2009, 126-129