INTRODUCTION:

Glipizide is an anti-diabetic drug under sulfonylurea category. Sulfonylureas are weal acids due to the marked delocalization of the nitrogen lone electron pair by the sulfonyl group¹. Structurally, glipizide is a cyclohexysulfonylurea analogue similar to acetohexamide and glyburide. The drug is absorbed rapidly on oral administration. Its serum half-life is 2-4hr, and it has a hypoglycemic effect that ranges from 12-24hrs². In patients with impaired renal function, gliclazide, glipizide or tolbutamide are preffered since they are not excreted by the kidney. Generally, it is prudent to start at the lowest recommended dose in order to minimize risk of hypoglycemia³. Glipizide is intermediate between tolbutamide and chlorpropamide and is useful alternative to chlorpropamide in patients who do not tolerate it because of GI adverse effect or allergic reactions⁴. Glipizide reach peak plasma level in 1hr. Most is metabolized in the liver to inactive products which are excreted in urine. 12% is excreted in faeces. Glipizide may cause hypoglycemia. It has diuretic action⁵. Glipizide is fast acting, insulineumatic action, persists even after prolonged use, can be given once daily despite short half life. Glipizide is preferred when a fasten and shorter acting drug is required⁶. There are very few methods described in literature for the determination of glipizide. All of them use high-performance liquid chromatography (HPLC)⁷. The drug has been determined in human plasma using LC/MS technique⁸.

EXPERIMENTAL:

Chemicals and Solvents:

HPLC grade methanol and phosphase buffer (pH 3.4) were used for preparing the mobile phase. Pure sample of glipizide (Sun Pharmaceutical Ltd) and commercial samples of tablets containing the drug namely Glucotrol (Jenburkt Pharmaceutical Ltd) were employed in the study.

Chromatographic Conditions:

A gradient HPLC system with YoungLin SP930D solvent delivery pump, a RP C18 Column (Inertsil C18, 250mm * 4.6 mm, 5μ), a UV dual wavelength detector YoungLin UV730D for HPLC was employed. Autochro-3000 was used as a software for running HPLC system that is 32 bit and fully compatible with MS Window XP.

All the solutions was filtered through 0.2 μm membrane filter

Estimation of Glipizide:

For Glipizide: 100mg of glipizide was accurately weighed and transferred to a 100ml volumetric flask and dissolved in methanol. (Stock A: 100 μg/ml). Aliquots of Stock A were further diluted to get the concentration of 15,30,45,60,75 μg/ml.

To establish the linearity of analytical method, a series of dilution ranging from 15-75 μg/ml were prepared. All the solutions was filtered through 0.2 μm membrane filter and injected, chromatograms was recorded and it was repeated for six times. A calibration graph was plotted between the mean peak area vs. respective concentration and regression equation was derived. The flow rate was kept 1ml/min. Each of the dilutions was injected 6 times into the column and the corresponding chromatograms were obtained.

Estimation of the Drug in Tablet Dosage Form:

Commercial brand of Glucotrol (Jenburkt Pharmaceutical Ltd) were employed in the study. Twenty tablets were accurately weighed and average weight was determined. Tablets were powdered and powder equivalent to 100mg per tablet of glipizide was taken accurately weighed and transgerred into two respective volumetric flask (100ml). This was dissolved in methanol and sonicate for 3min. The volume was made up to mark and filtered through Whatmann’s filter paper. Filter was further diluted with to get the final dilution. The response of final dilutions were observed at selected wavelength and the concentration were obtained from equation. The procedure was repeated for three times. The mean peak area of the drug was calculated and the drug content in the tablets was quantified using regression equation obtained for the pure sample.

RESULT AND DISCUSSION:

The present study was aimed at developing a sensitive, precise and accurate HPLC method for the analysis of Glipizide in pharmaceutical dosage form. For this, a binary mixture of methanol and phosphate buffer (55:45 v/v) portion was found to be most suitable mobile phase as the peaks obtained were sharp, better resolved and almost free from tailing (Fig.-1). The retention time for Glipizide was 7.098min. The calibration range was found to be in the range of 15-75 μg/ml (r²= 0.999) for glipizide. y=60113x+17434 y= area of curve, m= slope, x= concentration, c= intercept (Table-1 and 2).

Figure 1: A model chromatogram of Glipizide and Internal Standard (Caffiene)

Table 1. Calibration of the Proposed Method

Concentration of Glipizide μg/ml.	Peak area
15	895780
30	1796805.16
45	2595865.16
60	3607240.66
75	4525219.66

Table 2: Regression Characters of the Proposed HPLC Method

Parameters	Value
Slope	60113
Intercept	17434
Correlation coefficient (r)	0.999

The drug content in the tablets was quantified using the proposed method of analysis. The mean amount of Glipizide obtained in tablet dosage form was found to be 99.59% (table-4). This reveals that the method is quite precise. The absence of additional peaks in the chromatogram indicated non interference of the common excipients used in the tablets.

It can be concluded that the proposed HPLC method is sensitive and reproducible for the analysis of Glipizide in pharmaceutical dosage form in a short analysis time. The method was duly validated by evaluation of the required parameters (table-3).

Table 3: Day to Day and Analyst to Analyst Precision of the Proposed Method

Concentration of Glipizide μg/ml.	Observed concentration of Glipizide μg/ml.
	Day to Day		Analyst to Analyst
	Mean (n=3)	RSD (%)	Mean (n=3)	RSD (%)
15	15.83	105.5	15.17	101.13
30	30.163	100.54	30.16	100.54

Table 4: Assay of Glipizide in Tablet Dosage Form

Brand name of the Tablet	Labeled amount of drug (mg)	Mean amount found by the proposed method	Mean % labeled amount
Glucotrol	5	5.05	101.0

REFERENCES:

1. Williams and Lemke, Foye’s Principles of Medicinal Chemistry, 2002, 5, 643.

2. Wilson and Gisvold’s Textbook of Organic Medicinal and Pharmaceutical Chemistry, 1998, 10, 627.

3. Bennet PN, Brown MJ, Clinical Pharmacology, 2003, 9, 688.

4. Satoskar RS, Bhandarkar SD, Ainapure SS, Pharmacology and Pharmacotherapeutics, 2001, 17, 908.

5. Rang HP, Dale MM, Ritter JM, Pharmacology, 2000, 4, 395.

6. Tripathi KD, Essential of Medicinal Pharmacology, 2003, 5, 246.

7. Jing Yao, Ya-Qin Shi, Zhuo-Rong Li and Show-Hong Jin, RP-HPLC method for screening potentially counterfit anti-diabetic drugs, Journal of chromatography B, 2007, 853, 254.

8. Cun-Gang Ding, Zhen Zhou, Qing-Hua Gi, Xiao-Jin Jhi, Li-Li Ma, simultaneous determination of metformin and glipizide in human plasma by liquid chromatography-tendem mass spectrometry, Biomedical chromatography, 2007, 21, 132.

Received on 22.02.2011 Modified on 01.04.2011

Research J. Pharm. and Tech. 4(6): June 2011; Page 949-950