1. INTRODUCTION:

Desloratidine (DES) is 8- Chloro-6; 1- dihydro-11 (-4 piperidinylidine) -5H- benzo [5, 6] Cycloheptal [1, 2-b] pyridine, descarboethoxyloratidine. C₁₉H₁₉ClN₂^1,
2having molecular weight 310.82. It is not yet official inany Pharmacopoeia. It is non-sedating peripheral-histamine H1 receptor antagonist, active metabolite of loratidine. A survey of literature reveals that DES is estimated by HPLC^3,4, HPTLC⁵, spectrophotometry⁶, special data analysis⁷.

Pseudoephedrine Hydrochloride (PSEH) is orally active direct and indirect sympathomimetic upper respiratory tract decongestant drug, chemically (1S,2S) -2- methylamino -1- phenylpropan-1-ol hydrochloride, has sympathomimetic activity⁸ and is official in the United States Pharmacopoeia⁹, British Pharmacopoeia¹⁰ and Indian Pharmacopoeia ¹¹. The pharmacopoeia describes HPLC method for estimation of pseudoephedrine hydrochloride from tablet formulation. Several HPLC methods^{12, 13} and few LC/MS methods^{14, 15} are reported for the estimation of pseudoephedrine hydrochloride.

Both the drugs are formulated in a binary solid dosage form for the treatment of allergic conditions like allergic rhinitis, cough and cold for relief of nasal decongestion. Literature survey revealed that single HPLC method^16,19 has been reported for the simultaneous estimation of both these components in a combined dosage form. There is no spectrophotometric method has been reported for estimation of this combination.¹⁸ The aim of this study was to develop the simultaneous equation (Vierodt’s) method, for estimating Desloratadine and Pseudoephedrine Hydrochloride simultaneously from Tablets and Dissolution media. In the proposed method no separation is required and the method is fast and convenient.

2. MATERIALS AND METHODS:

Instrument used is UV-Visible double beam spectrophotometer, Make: Jasco, Model No. V 530 with spectral band width of 2 nm, data pitch 0.5 nm and pair of 10mm matched quartz cells. Pure drug sample of Desloratadine and Pseudoephedrine Hydrochloride were obtained as gift sample from Micro Advanced Research Center, Micro Labs. Bangalore. Hydrochloric Acid, Potassium Dihydrogen Phosphate, Sodium Chloride, Ethanol, AR grade were purchased from Loba chemie.

Preparation of stock solution:

Accurately weighed quantity of Desloratadine (10mg) and Pseudoephedrine Hydrochloride (100mg) was transferred into two separate 100ml volumetric flasks, dissolved in 0.1N HCl (Stock solution: 100 µg/ml of Desloratadine and 1000 ug/ml of Pseudoephedrine Hydrochloride). Similarly Accurately weighed quantity of Desloratadine (10mg) and Pseudoephedrine Hydrochloride (100mg) was transferred into two separate 100ml volumetric flasks, dissolved in 20 ml Ethanol and diluted to the mark with 0.1M Potassium Phosphate Buffer P^H 7.5.

Calibration curve:

From stock solution in 0.1N HCL, working standard solution of drugs was prepared by appropriate dilution with 0.1N HCL and was scanned in entire UV range to determine λ_max Desloratadine has λ_max of 281.5 nm while Pseudoephedrine Hydrochloride has 256.5 nm in (fig 1). Similarly From stock solution in 0.1M Potassium Phosphate Buffer P^H 7.5, working standard solution of drugs was prepared by appropriate dilution with Phosphate Buffer and was scanned in entire UV range to determine λ_max Desloratadine has λ_max of 241.5 nm while Pseudoephedrine Hydrochloride has 256.5 nm in (fig 2). Linearity of system was investigated by serially dilution the stock solution to give concentration in range of 2.5-25 µg/ml for Desloratadine and 120-960 µg/ml for Pseudoephedrine Hydrochloride in (table 1).

Fig.1. UV Overlain spectra of Desloratadine and Pseudoephedrine Hydrochloride in 0.1 N HCL.

Fig.2. UV Overlain spectra of Desloratadine and Pseudoephedrine Hydrochloride in Phosphate Buffer P^H 7.5.

Table 1: Statistical data of regression equations and validation parameters for

Desloratadine and Pseudoephedrine Hydrochloride.

Parameters	0.1N HCL	0.1M Potassium Phosphate Buffer P^H 7.5
Desloratadine
Slope	0.0335	0.0401
Intercept	0.0153	0.0119
Regression coefficient	0.9995	0.9997
Beer’s lamberts range in µg/ml	2.5 – 25	2.5 – 25
Limit of detection in µg/ml	0.2460	0.4455
Limit of quantification in µg/ml	0.7455	1.3501
Pseudoephedrine Hydrochloride
Slope	0.0009	0.0009
Intercept	0.0039	0.004
Regression coefficient	0.9997	0.9997
Beer’s lamberts range in µg/ml	120 – 960	120 – 960
Limit of detection in µg/ml	13.3309	11.6693
Limit of quantification in µg/ml	40.3938	35.36

Simultaneous equation method:

The absorptivity values of the drug were determined at the λ_maxof Desloratadine and Pseudoephedrine Hydrochloride in 0.1N HCL. The absorptivity value of the drug is the ratio of absorbance at selected wavelength with concentration of drug in µg/ml. A set of two simultaneous equations (in two variables C₁ and C₂) were formed using these Absorptivity coefficient values.

A₁ = (0.03166) C₁ + (0.00000959) C₂………………… (1)

A₂ = (0.02075) C₁ + (0.0008982) C₂………………… (2)

Where, C₁ and C₂ are concentrations of DES and PSEH measured in µg/ml, in sample solutions. A₁ and A₂ are absorbance of mixture at selected wavelength 281.5 nm and 256.5 nm respectively.

By applying the Cramer’s rule ¹⁷ to equation (1) and (2), the concentration C_DES and C_PSEH, can be obtained as follows.

A₂ (0.00000959) – A₁ (0.0008982)

C_DES = ………………………………………. ………….. (3)

(-0.00002824)

A₁ (0.02075) – A₂ (0.03166)

C_PSEH = ………………………………… ………….. (4)

(-0.00002824)

Similarly the absorptivity values of the drug were determined at the λ_maxof Desloratadine and Pseudoephedrine Hydrochloride in 0.1M Potassium Phosphate Buffer P^H 7.5. A set of two simultaneous equations (in two variables C₁ and C₂) were formed using these Absorptivity coefficient values.

A₁ = (0.04056) C₁ + (0.0004020) C₂……………….. (5)

A₂ = (0.03023) C₁ + (0.0009190) C₂……………….. (6)

Where C₁ and C₂ are concentrations of DES and PSEH measured in µg/ml, in sample solutions. A₁ and A₂ are absorbance of mixture at selected wavelength 281.5 nm and 256.5 nm respectively.

By applying the Cramer’s rule to equation 1 and 2, the concentration C_DES and C_PSEH, can be obtained as follows.

A₂ (0.0004020) – A₁ (0.0009190)

C_DES = ……………………………………… ………….. (7)

(-0.00002512)

A₁ (0.03023) – A₂ (0.04056)

C_PSEH = ………………………………. ………….. (8)

(-0.00002512)

Assay of formulation:

The average weight quantity (1.2gm) of twenty tablets, (Content Desloratadine 2.5 mg and Pseudoephedrine Hydrochloride 120 mg) was transferred to 100 ml volumetric flask and dissolved in 0.1N HCL by intermittent shaking and volume was made up to 100 ml with same solvent. The solution was filtered through a Whatmann filter paper. The solution diluted with 0.1N HCL to obtained 2.5 mg DES and 120 mg PSEH. Absorbance of sample solution were recorded at 281.5 nm and 256.5 nm and concentration of two drugs in sample were determined by using Simultaneous equations in (table 2). The analysis procedure was repeated six times.

Table 2: Results of simultaneous estimation of Tablet formulation.

Parameters	0.1N HCL	0.1M Potassium Phosphate Buffer P^H 7.5
Desloratadine
Label claim mg/tab.	5	5
Amount found^* mg/tab.	4.94	4.94
Label claim %	98.96	98.83
S.D.^*	0.04875	0.0725
%R.S.D.^*	0.9852	1.4671
Pseudoephedrine Hydrochloride
Label claim mg/tab.	120	120
Amount found^* mg/tab.	119.83	119.85
Label claim %	99.86	99.88
S.D.^*	0.4307	0.1511
%R.S.D.^*	0.3594	0.1261

*Mean of six estimation; S.D.: Standard Deviation; R.S.D.: Relative Standard Deviation;

Similarly the average weight quantity (1.2gm) of twenty tablets, (Content Desloratadine 2.5 mg and Pseudoephedrine Hydrochloride 120 mg) was transferred to 100 ml volumetric flask and dissolved in small quantity of Ethanol and diluted to the mark with 0.1M Potassium Phosphate Buffer P^H 7.5 by intermittent shaking and volume was made up to 100 ml with same solvent. The solution was filtered through a Whatmann filter paper. The solution diluted with Phosphate Buffer to obtained 2.5 mg DES and 120 mg PSEH. Absorbance of sample solution were recorded at 241.5 nm and 256.5 nm and concentration of two drugs in sample were determined by using Simultaneous equations in (table 2). The analysis procedure was repeated six times.

3. VALIDATION:

Accuracy:

Accuracy of the developed method was confirmed by doing recovery study as per ICH norms at three different concentration levels- 80%, 100%, 120%. Here to a preanalysed sample solution, standard drug solutions were added and then percentage of drug content was calculated. The result of accuracy study was reported in (table 3).

From the recovery study it was clear that the method is very accurate for quantitative estimation of Desloratidine and Pseudoephedrine Hydrochloride form tablet dosage form as the statistical results were within the acceptance range i.e. R.S.D. < 1.5.

Table 3: Results of recovery studies:

Level of recovery	Amt. of drug added. µg/ml	Drug	0.1N HCL		0.1M Potassium Phosphate Buffer P^H 7.5
Level of recovery	Amt. of drug added. µg/ml	Drug	Recovery %*	%R.S.D.^*	Recovery %*	%R.S.D.^*
80 %	4	DES	98.73	0.50	98.49	0.60
80 %	96	PSEH	99.37	0.90	98.68	0.45
100 %	5	DES	98.63	0.55	99.11	0.83
100 %	120	PSEH	99.44	0.47	98.92	1.03
120 %	6	DES	99.54	1.20	98.63	0.48
120 %	144	PSEH	99.05	1.37	99.22	0.68

*Mean of six estimation; DES = Desloratadine; PSEH = Pseudoephedrine Hydrochloride;

R.S.D.: Relative Standard Déviation

Table 4: Precision study:

Drug	Concentration in µg/ml	0.1N HCL		0.1M Potassium Phosphate Buffer P^H 7.5
		% RSD*		% RSD*
		Intra-day	Inter-day	Intra-day	Inter-day
DES	2.5	0.28	0.57	0.64	0.89
	5.0	0.23	0.72	0.60	0.80
	7.5	0.49	0.89	0.96	0.56
	10	0.17	0.80	0.16	0.32
	12.5	0.44	0.82	0.20	0.35
PSEH	120	0.35	0.77	0.58	0.75
	240	0.41	0.27	0.40	0.74
	360	0.49	0.77	0.10	0.62
	480	0.14	0.93	0.17	0.66
	600	0.33	0.69	0.14	0.95

*Mean of six estimation; DES = Desloratadine; PSEH = Pseudoephedrine Hydrochloride;

R.S.D.: Relative Standard Déviation

Precision:

Precision was determined by studying the repeatability and intermediate precision. Intermediate precision was carried out by doing intra and inter day precision study. In intraday study concentration of five drugs were calculated on the same day at an interval of one hour. In inter day study the concentration of drug contents were calculated on three different days study expresses within laboratory variation in different days. In both intra and inter-day precision study for the methods %R.S,D. were not more than 1.5% indicates good intermediate precision (table 4).

Linearity:

For each drug, appropriate dilutions of standard stock solutions were assayed as per the developed methods. The Beer- Lambert’s concentration range was found to be 2.5-25 µg/ml for Desloratadine and 120-960 µg/ml for Pseudoephedrine Hydrochloride in (table 1).

Limit of Detection (LOD) and Limit of Quantitation (LOQ):

The LOD and LOQ of Pseudoephidrine Hydrochloride and Desloratidine by proposed methods were determined using calibration standards. LOD and LOQ were calculated as 3.3/S and 10/S, respectively, where S is the slope of the calibration curve and is the standard deviation of response. The results of the same are shown in (table 1).

4. RESULT AND DISSCUSION:

The proposed method was found to be simple and linear in the concentration range of 2.5 to 25 µg/ml for Desloratidine and 120 to 960 mg/ml for Pseudoephidrine Hydrochloride respectively. The method was found to be accurate and precise as indicated by recovery studies and % RSD not more than 1.5. Thus the method is specific and sensitive.

5. CONCLUSION:

The proposed spectrophotometric methods for the simultaneous estimation of for Desloratadine and Pseudoephidrine Hydrochloride from Tablets formulation and Dissolution media was found to be sensitive, accurate, precise, simple and rapid.

6. REFERENCE:

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Received on 16.07.2011 Modified on 14.08.2011

Asian J. Research Chem. 4(9): Sept, 2011; Page 1440-1443