Metformin:

Metformin is an oral antidiabetic drug in the biguanide class, first-line drug of choice for the treatment of type 2 diabetes, in peculiar, in over weight and obese people and those with normal kidney function. Metformin’s use in gestational diabetes has been limited by safety matters. It is also used in the treatment of polycystic ovary syndrome, has been investigated for other diseases where insulin resistance may be an important factor, it works by suppressing glucose production by the liver.

       
           
       
Fig 1:  Structure of Metformin

IUPAC Name: 1-Carbamimidamido-N,N-Dimethyl methanimidamide

Molecular formula: C4H11N5

Molecular weight: 129.1636 g/moll

Half-life: 6.2 hours. Duration of action is

8-12 hours.

Category: Antidiuretic Agents

TELMISARTAN:

Telmisartan is an angiotensin II receptor antagonist (ARB) used in the management of hypertension. Generally, angiotensin II receptor blockers (ARBs) such as telmisartan bind to the angiotensin II type 1 (AT1) receptors with high affinity, causing inhibition of the action of angiotensin II on vascular smooth muscle, ultimately leading to a reduction in arterial blood pressure. Recent studies suggest that telmisartan may also have PPAR-gamma agonistic properties that could potentially confer beneficial metabolic effects.

       
           
       
Fig: 2 Structure of Telmisartan

IUPAC Name:  2-(4-{[4-methyl-6-(1-methyl-1H-1,3- benzodiazol-2-yl)-2-propyl-1H-1,3-

benzodiazol-1-yl]methyl}phenyl)benzoicacid

Molecular formula: C33H30N4O

Molecular weight: 5 14.64gm/mol

Half-life: Bi-exponential decay kinetics with a terminal elimination half-life of approximately 24 hours.

Category: Antihypertensive

MATERIALS AND METHODS

Materials:

Metformin and Telmesartan, Combination Metformin and Telmesartan tablets, distilled water, acetonitrile, phosphate buffer, ammonium acetate buffer, glacialacitic acid, methanol, potassium dihydrogen phosphate buffer, tetra hydrofuran, tri ethyl amine, ortho-phosphoric acid etc.

Instrument:

1. HPLC instrument used was of WATERS HPLC 2965 SYSTEM with Auto Injector and PDA Detector. Software used is Empower
2. UV-VIS spectrophotometer PG InstrumentsT60 with special bandwidth of 2mm and 10mm and matched quartz was be used for measuring absorbance for Metformin andTelmesartan solutions.

Methods:

Preparation of buffer:

Buffer: 1 ml OPAin a 1000mlof Volumetric flask add about 900ml of milli-Q water added and degas to sonicate and finally make up the volume with water then PH adjusted to 3.6 with dil. Orthophosphoric acid solution.

Standard Preparation: (250µg/ml Metformin and 20µg/ml Telmisartan)

Accurately Weighed and transferred 25mg&5mg of Metformin and Telmisartan working Standards into 10 ml and 25ml clean dry volumetric flasks seperately, add 3/4^th ml of diluent, sonicated for 30 minutes and make up to the final volume with diluents. From the above each stock solutions, 1 ml was pipeted out in to a 10ml Volumetric flask and then make up to the final volumewith diluent.

Sample preparation: 5 tablets were weighed and calculate the average weight of each tablet then the weight equivalent to 5 tablets was transferred into a 100ml volumetric flask, 70ml of diluent added and sonicated for 30 min, further the volume made up with diluent and filtered. From the filtered solution 0.1ml was pipeted out into a 10 ml volumetric flask and made upto 10ml with diluent. 

Method Development:

Trial 1

Column Used                  : Kromosil 150 x 4.6 mm, 5m.

Mobile phase                : Buffer methanol (50:50)

Flow rate                        : 1ml/min

Wavelength                   : 210nm

Temperature                 : 30 ? C

Injection Volume          : 10µl

       
           
       
Fig: 3 Trial chromatogram 1

Trial 2

Column Used        :    Xterra 150 x 4.6 mm, 5m.

Mobile phase         :  Buffer: Acetonitrile methanol (50:40:10)

Flow rate                    : 1ml/min

Wavelength              : 210nm

Temperature             : 30 ? C

Injection Volume        : 10µl

       
           
       
Fig: 2 Trial chromatogram 2

Trial 3:

Column Used              :  Xterra 150 x 4.6 mm, 5m.

Buffer used                  : 0.1% OPA

Mobile phase                : Buffer: acetonitrile (55:45A)

Flow rate                       : 1ml/min

Wavelength                 :    210nm

Temperature               : 30 ? C

Injection Volume        : 10µl

       
           
       
Fig: 3 Trial chromatogram 3

Optimized Method: Drugs were eluted with good retention time, resolution; all the system suitable parameters like Plate count and Tailing factor were within the limits.

Column Used        : Xterra150 x 4.6 mm, 5m.

Buffer used            : 0.1% OPA

Mobile phase           :  Buffer: Acetonitrile (60:40A)

Flow rate                :  1ml/min

Diluent                    : Water: methanol 50:50

Wavelength             : 210nm

Temperature          :  30 ? C

Injection Volume   : 10µl

System suitability: All the system suitability parameters are within range and satisfactory as per ICH guidelines.

Table: 1 System suitability studies of Metformin and Telmesartan

       
           
       
Fig: 5 Typical chromatogram of Metformin and Telmesartan

Linearity: Six Linear concentrations 50ppm - 300ppm of Metformin and 5ppm - 30ppm of Telmesartan are prepared and Injected.Regression equation of theMetformin and Telmesartan are found to bey = 16786x + 673.7 and y = 40365x + 1626 and regression co-efficient was 0.999.

Table:2 Calibrationdata of Metformin and Telmesartan

       
           
       
Fig: 6 Calibration curve of Metformin

       
           
       
Fig:6 Calibration curve of Telmesartan

Intraday precision (Repeatability): Intraday Precision was performed and % RSD for Metformin and Telmesartan were found to be 0.43% and 1.04% respectively.

Table: 3 Repeatability data forMetformin and Telmesartan

       
           
       
Fig: 7 Repeatability Chromatogram of Metformin and Telmesartan

Accuracy: Three concentrations 50%, 100%, 150%, were injected in a triplicate manner and amount Recovered and % Recovery were displayed in

Table 4. Accuracy data of Metformin and Telmesartan

       
           
       
Robustness: Small deliberatechanges in method like Flow rate, mobile phase ratio, and temperature are made but there were no recognized change in the result and are within range as per ICH Guide lines.

SUMMARY AND CONCLUSIONS:

Table: 7. Summary Table