Two Wavelength Method for Estimation of Risperidone and Trihexyphenidyl HCl in Combined Tablet Dosage Form

 

AB Roge*, Dr. G R Shendarkar, Dr. N Y Gond, Dr. N B Ghiware, Dr. S M Vadvalkar

Nanded Pharmacy College, Opp- Kasturba Matru Seva kendra, Shyam Nagar, Nanded -431605, Maharashtra, India

*Corresponding Author E-mail: ashishkhushi9@gmail.com

ABSTRACT:

No one UV Spectrophotometric method is available for simultaneous estimation of Risperidone (RIS) and Trihexyphenidyl HCL (THP). The objective of present work is to develop a new, simple, accurate and sensitive UV-spectrophotometric two wavelength method for simultaneous determination of RIS and THP in combined pharmaceutical dosage form. Two wavelength i,e 238 nm and 271 nm were selected for estimation of RIS where as wavelength 217 nm was selected  for estimation of THP using 0.1 N HCL solution as solvent . RIS and THP shows linearity in the concentration range of 0-40 μg/ml and 0-80 μg/ml respectively. The method was validated statistically.

 

 

INTRODUCTION:

Risperidone (RIS) is psychotropic agent used to treat schizophrenia, action of which is mediated through a combination of dopamine Type 2 (D ₂ ) and serotonin Type 2(5HT₂) receptor antagonism. It is a selective monoaminergic antagonist with high affinity for 5HT₂, D₂ and H1 histaminergic receptors¹. It belongs to chemical class of benzisoxazole derivatives and is 3-[2-[4-(6-Fluoro-1,2-benzisoxazol-3-yl)-1-piperidinyl]ethyl]-6,7,8,9-tetrahydro-2-methyl-4H-pyrido-[1,2-a]-pyrimidin-4-one with molecular formula of  C₂₃H ₂₇ FN ₄ O ₂ and molecular weight of 410.49.

 

Literature survey revealed that various methods have been reported for estimation of RIS in biological matrices such as plasma with help of liquid chromatography (LC) ^2,3 , LC with diode array detection ⁴, LC with tandem mass spectrometry ^5,6,7 and LC with electrochemical detection ⁸. Few stability-indicating methods have been reported for determination of RIS in bulk powder and tablets in presence of its degradation products ^9,10.

 

Benzhexol hydrochloride or Trihexyphenidyl hydrochloride (THP); 1-Cyclohexyl-1-phenyl-3-(1-piperidyl) propan-1-ol hydrochloride (IUPAC) is used to treat the stiffness, tremors, spasms, and poor muscle control of Parkinson's disease. Molecular formula of THP is C₂₀H₃₁NO, HCl and molecular weight of 337.9 ¹¹. THP is official in BP and USP NF ^12,13. Literature survey revealed that HPLC ^14,15 methods have been reported for the estimation of Risperidone and Trihexyphenidyl individually and with other drugs in pharmaceutical dosage forms. Literature review revealed that no spectrophotometric method is yet reported for the simultaneous estimation of the RIS and THP in combined tablet dosage form. Therefore, it was thought worthwhile to develop simple, precise, accurate spectrophotometric method for simultaneous estimation of RIS and THP in combined tablet dosage form.

 

For this purpose marketed tablets RIDON PLUS -3 containing 3 mg of RIS and 2 mg of THP was used.

 

MATERIAL AND METHOD:

Double beam UV–visible spectrophotometer UV 2401 PC (Japan) Thermo, with 1cm UV matched quartz cells was used. Citizen Balance was used for experimental purpose. Pharmaceutical grade RIS (Batch No. TRS PP 9004) and THP (Batch No. PD/TH/0913) were supplied as a gift sample by Talent India, Ahmadabad, (Gujarat), India. The tablet dosage form (RIDON PLUS 3, Batch No. 06R13, Mfg. Dt. 05/09 and Exp. Dt. 11/11)  was procured from the local market (Label claim: 3 mg RIS and 2 mg THP) marketed by KIVI Lab, Baroda. 

 

Fig.1: Overlain spectra of RIS and THP

 

Fig. 2: Plot of Beer-Lambert study for RIS at 217, 238 and 271 nm

 

Preparation of standard solution:

Risperidone stock standard solution:

An accurately weighed quantity of RIS 10 mg was transferred to the 100 mL volumetric flask and dissolved in 25 ml of 0.1N HCL and sonicate for 5 min. The volume was made up to the mark with 0.1N HCL (100 mg/mL).     

 

Trihexyphenidyl HCL stock standard solution:

An accurately weighed quantity of THP 20 mg was transferred to the 100 mL volumetric flask and dissolved in 25ml  of 0.1N HCL and sonicate for 5 min . The volume was made up to the mark with the 0.1N HCL (200 mg/mL).

 

Study of spectra and selection of wavelength:

The aliquot portions of stock standard solutions of RIS and THP were diluted appropriately with solvent to obtain concentration 20 mg/mL of each drug. The solutions were scanned in the range of 400 – 200 nm in 1 cm cell against blank. The overlain UV absorbance spectrum of RIS and THP is shown Fig.1.

From the overlain spectrum shown in Fig.1, the wavelength selected for estimation of RIS was 238 nm and 271 nm, where as for THP was 217 nm. At 217 nm, there was considerable absorbance of Risperidone. The RIS and THP obey Beer’s law in the concentration range of 0 to 40 μg/ml and 0 to 80 μg/ml at selected wavelength as shown in Fig.2.

 

Quantitative estimation of these drugs was carried out by using following formulae’s.

A concentration of RIS is calculated from slope and intercepts equation of caliberation curve of A 238.0 nm - A 271.0 nm against concentration of RIS.

Cy                      µ  A _{238.0 nm} - A _{271.0 nm.}                                    (1)  

(Conc. of drug is proportional to absorbance difference between two wavelengths is principle of two wavelength method)

A217  =   Ay 217+ Ax 217

A217  = Cy x a_{y 217} + Cx x a_{x 217}

                     A217 - Cy x a_{y 217}

   Cx     _{=                 -----------------------------------------}

                           a_{x 217}

Where,

Cx concentration (g /100ml) of THP

Cy concentration (g /100ml) of RIS

A238 nm and A271.0 nm are absorbance of mixture at 238 nm and 271.0 nm, respectively,

Ay 217 nm and Ax 217.0 nm are absorbance of RIS and THP at 217.0 nm, respectively,

a_y 217 nm and a_x 217  = Absorptivity of RIS and THP at 217 nm

 

Estimation of drugs in commercial tablet formulation:

Twenty tablets were accurately weighed. Average weight of tablet was calculated. The tablets were reduced to fine powder and mixed thoroughly. A quantity of tablet powder equivalent to weight of one tablet was transferred to 100 mL volumetric flask and dissolved in 25 ml of solvent i.e. 0.1N HCL and sonicate for 5 min. and volume was made to 100 mL with the same solvent to get final concentration of about 30 mg/mL RIS and 20 mg/mL THP. The solution was filtered through Whatman filter paper no. 41.  The absorbance of sample solution was measured at 217 nm, 238 nm and 271 nm in 1 cm cell against blank.

 

Validation:

The proposed method was validated on the basis of parameters namely accuracy, precision, ruggedness and linearity and range. The accuracy of the proposed method was ascertained by carrying out recovery studies using standard addition method. The recovery study was performed to determine if there was any positive or negative interference from excipients present in the formulation. Precision of an analytical method is expressed as SD or RSD of a series of measurements. It was ascertained by replicate estimation of drug by the proposed method. Test for ruggedness was carried out by repeating the procedure under different conditions, i.e., on different days, at different time and by different analysts. Linearity and range study was done by preparing concentration in the range of 80 -120 % of test concentration and absorbance values were recorded at 217 nm, 238 nm and 271 nm. The plot of linearity and range is shown in Fig. 3.

 

RESULTS AND DISCUSSION:

An attempt has been made to develop a fast, sensitive, precise, reproducible and economical analytical method for simultaneous estimation of RIS and THP in their combined dosage form. In this method RIS and THP obey Beer’s law in the concentration range of 0 to 40 μg/ml and 0 to 80 μg/ml. It was observed that both the drugs showed additivity of absorbance at selected wavelengths indicating that both the drugs do not interact with each other in the solvent system used. A (1%, 1cm) values were also calculated for both the drugs. For THP, A (1%, 1cm) was found to be 104.8 at wavelength 217 nm and for RIS, it was 203.1 at wavelength 217 nm respectively. The result of percentage estimation of drug is shown in Table 1. The method was validated as per the ICH and USP guidelines. The results of recovery study were found to be within the prescribed limit of 98 - 102 %, proving the accuracy and showing that the method is free from interference from excipients. The results are shown in Table 2. For precision, replicate estimation of both RIS and THP in the same batch of tablets was done by proposed method, which yielded quite concurrent results, indicating reliability of the method. The values of SD or RSD are within the prescribed limit of 2 %, showing high precision of the method, as shown in Table 1. For ruggedness the proposed method was repeated under different conditions like different time, on different day and by different analyst. The results shown in Table 3 prove that the method is reproducible.

 

 

Table 1: Result of estimation of RIS and THP in Tablet formulation

Sr. No.	Weight of tablet powder (gm)	Absorbance		% Lable claim
		A1-A2	A3	RIS	THP
1	117.6	0.529	0.812	99.3	99.75
2	117.7	0.527	0.809	98.8	99.12
3	117.9	0.532	0.817	99.6	100.5
			Mean	99.23	99.79
			± S.D.	0.404	0.557
			C.V.	0.407	0.558

Brand Name   RIDON PLUS 3                  Average weight =117.8 mg

 

Table 2:  Results of recovery studies of RIS and THP

Sr. No	Weight of Tablet Powder in  mg.	Amt. Added in      µg.		Absorbance		Amt. Recoverd in µg.			% Recovery
		RIS	THP	A1-A2	A3	RIS		THP	RIS	THP
1	117.8	3	2	0.581	0.896	2.97		1.98	99.3	99.4
2		3	2	0.584	0.897	2.99		1.99	99.75	99.8
3		6	4	0.632	0.977	5.93		3.99	98.9	99.76
4		6	4	0.635	0.978	5.96		3.96	99.4	99.1
5		9	6	0.691	1.059	8.98		5.95	99.8	99.25
6		9	6	0.689	1.06	8.96		5.99	99.6	99.89
							Mean		99.45	99.53
							±  S.D.		0.335	0.327
							C.V.		0.337	0.328

 

Fig. 3:  Plot of linearity and range for RIS and THP

 

During the linearity study it was observed that absorbance values of RIS and THP in the marketed formulation were linear in the range of 80 % to 120 % of the test concentration with R² close to one for this method of analysis as shown in Fig. 3. From the study of validation parameters namely accuracy, precision (SD and RSD), ruggedness (interday, intraday and different analyst), linearity and range, it was observed that the method is specific, accurate, precise, reproducible and rugged. Hence, this method can be employed for routine analysis of tablet dosage form.

 

Table 3: Summary of result of Ruggedness studies

 

ACKNOWLEDGEMENTS:

The authors are thankful to Talent India, Ahmadabad for providing gift sample of Risperidone and Trihexyphenidyl HCL.

 

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Received on 08.11.2012         Modified on 24.11.2012

Accepted on 28.11.2012         © AJRC All right reserved