## STP FOR LINEZOLID TABLETS

1.0) Description: Visual

2.0) Average Weight: Check weight of 20 tablets at randomly and calculate the average weight by formula :

wt of 20 tablets (gm) x 1000 / 20. found avg. wt in mg

3.0) Uniformity of weight:

Weigh 20 tablets selected at random and calculate the average weight. Not more than two of the individual weights deviate from the average weight by more than the percentage shown in table.

Weigh the tablets individually and calculate the percentage of deviation for each tablet. By using formula = (experimental weight – theoretical weight)    x 100%

Theoretical weight

 Average weight of tablets Percentage deviation More than 80mg but Less than 250mg 7.5% 250mg or More 5%

4.0) Identification Test:

In the assay, the principal peak in the chromatogram obtained with the test solution corresponds to the peak in the chromatogram obtained with the reference solution.

5.0)      Hardness:

The standard method used for tablet hardness testing is compression testing. The tablet is placed between two jaws that crush the tablet. The machine measures the force applied to the tablet and detects when it fractures. Although compressive force is applied to the tablet, along the diameter of the tablet at right angles to the applied force.

6.0)      Disintegration Time

Unless otherwise stated in the individual monograph, introduce one tablet into each tube and add a disc to each tube. The assembly is suspended in the liquid medium in a suitable vessel, preferably a 1-litre beaker. The volume of liquid is such that the wire mesh at its highest point is at least 15mm below the surface of the liquid, and at its lower point is at least 25mm above the bottom of the beaker. At no time should the top of the basket-rack assembly become submerged. There is a thermostatic arrangement for heating the liquid and maintaining the temperature at 37±2°.

If 1 or 2 tablets fail to disintegrate, repeat the test on 12 additional tablets; not less than 16 of the total of 18 tablets tested disintegrate.

If the tablets adhere to the disc and the preparation under examination fails to comply, repeat the test omitting the disc. The preparation complies with the test if all the tablets in the repeat test disintegrate.

7.0)      Dimension of Tablet:

Length, breadth and thickness are determined by vernier in mm

8.0)      Dissolution:

Medium: 900ml of buffer solution prepared by dissolving 6.8g of potassium dihydrogen orthophosphate and 0.9 g of sodium hydroxide             in 1000ml of water, adjusted to pH 6.8 with sodium hydroxide solution,

Speed: 50 rpm

Time:  30 minutes

Limit: NLT 75% of the labeled amount of linezolid is dissolved.

Withdraw a suitable volume of the medium and filter. Measure the absorbance of the filtered solution, suitably diluted with the medium if necessary, at the maximum at about 250nm. Calculate the content of Linezolid in the medium from the absorbance obtained from a solution of known concentration of Linezolid reference standard in the same medium.

9.0)      Leak test:

The apparatus is used to test for the integrity of packed strips, blisters and Alu-Alu Blister pack containing tablets. Ensure apparatus bath is filled with purified water up to mark indicated and add 0.5% crystal violet solution in water. Samples are placed into the desiccators and the lid is placed in position. The pump starts to produce a vacuum 15inHg inside the desiccators and the vacuum is held for 1 minute. The sample remains at the required vacuum level for given time interval buzzer will sound after time is over and will cut off the vacuum pump. As the package is immersed in a colored dye solution the venting of the desiccators will allow any holes to be penetrated by the dye and the contents of the flexible packaging will also be stained with the same coloring material.

Examine all the strips for any leakage by opening the pockets manually. If anyone pocket shows evidence of leakage, reject the sample, stop the Blister / Strip machine and immediately take corrective action.

10.0)    Related substances:

Determined by liquid chromatography.

Solvent mixture: A mixture of 75 volumes of buffer solution prepared by diluting 1.0ml of triethylamine to 1000ml with water, adjusted to pH 3.0 with O.P.A. and 25 volumes of methanol.

Test solution: Weigh and powder 20 tablets. Disperse a quantity of powder containing about 40mg of linezolid with 35ml of the solvent mixture, sonicate for 20 minutes and dilute to 50ml with the solvent mixture, filter.

Reference solution: A 0.0008 per cent w/v solution of Linezolid reference standard in the solvent mixture.

Chromatographic system:

• A stainless steel column 15cm X4.6mm, packed with octadecylsilane bonded to porous silica (5µm).
• Mobile phase: A. a mixture of 90 volumes of buffer solution prepared by mixing 1.0ml of triethylamine in 1000ml of water, adjusting to pH 3.0 with O.P.A. and 10 volumes of methanol,
1. a mixture of 10 volumes of buffer solution prepared by mixing 1.0ml of triethylamine in 1000ml of water, adjusted to pH 3.0 with O.P.A. and 90 volumes of methanol,
• Flow rate: 1ml per minute.
• Spectrophotometer set at 250nm,
• Injection volume: about 10µl
 Time (in min.) Mobile phase A ( per cent v/v) Mobile phase b ( per cent v/v) 0 90 10 35 65 35 45 20 80 47 20 80 48 90 10 55 90 10

Inject reference solution. Test is not valid unless the relative standard deviation for replicate injections is not more than 5.0 per cent.

Inject reference solution and test solution. In the chromatogram obtained with the test solution, the area of any secondary peak is not more than the peak in the chromatogram obtained with reference solution (1.0 per cent) and the sum of area of all the secondary peaks is not more than twice the area of the peak in the chromatogram obtained with the reference solution (2.0 per cent).

11.0)    Assay: Determined by liquid chromatography.

Solvent mixture: A mixture of 75 volumes of buffer solution prepared by diluting 1.0ml of triethylamine to 1000ml with water, adjusted pH 3.0 with O.P.A. and 25 volumes of methanol.

Test solution: Weigh and powder 20 tablets. Disperse a quantity of powder containing about 40mg of Linezolid with 35ml of the solvent mixture, sonicate for 20 minutes and dilute to 50ml with the solvent mixture, filter.

Reference solution: A 0.08 per cent w/v solution of linezolid reference standard in the solvent mixture. Dilute 5ml of this solution to 50ml with solvent mixture.

Chromatographic system:

• A stainless steel column 15cm X4.6mm, packed with octadecylsilane bonded to porous silica (5µm).
• Mobile phase: a mixture of 70 volumes of buffer solution prepared by dissolving 1ml of triethylamine to 1000ml with water, adjusted to pH 3 with O.P.A. and 30 volumes of acetonitrile,
• Flow rate: 1.5ml per minute.
• Column temperature: 40°
• Spectrophotometer set at 250nm,
• Injection volume: about 10µl

Inject reference solution. The test is not valid unless the tailing factor is not more than 2.0. The column efficiency is not less than 2000 theoretical plates. The relative standard deviation for replicate injections is not more than 2.0 per cent.

Inject the reference solution and test solution.

Calculate the content of Linezolid in the tablets.

Alternative Method: By UV Spectrophotometer

Test Solution: Weigh and powder 20 tablets. Weight sample equivalent to 50mg of Linezolid 100ml volumetric flask add 20ml 0.1 M HCl into it and sonicate to dissolve the test sample. Make up to mark with 0.1 M HCl. Filter and dilute 1ml of this solution to 50ml in 0.1 M HCl.

Reference Solution: Weigh 25mg of reference standard of Linezolid in 100ml of volumetric flask. Add 20ml 0.1 M HCl into it and sonicate to dissolve. Make up to mark with 0.1 M HCl. Dilute 1ml of this solution to 50ml with 0.1 M HCl.

Check Absorbance of test as well as reference standard at about 244nm in UV Spectrophotometer.

Calculate the content of Linezolid in the tablets.

Formula:

Abs. of Test      STD Wt.(mg)        1              100                    50            Potency

—————–X————–X———X—————–X——-X————–X Average wt.

Abs. of STD        100                     50       Test Wt.(mg)            1             100

Acceptance criteria: 90.0%-110.0%

12.0)    MICROBIOLOGICAL PURITY

Perform the test according to requirements of IP,

Total aerobic Microbial count (TAMC): NMT 103 CFU/g

Total combined yeasts/Moulds count (TYMC): NMT 102 CFU/g

Pathogens: in 1gm drug.

Escherichia Coli – Should be absent

Pseudomonas aeroginosa – Should be absent

Salmonella – Should be absent

Staphylococcus aureus– Should be absent

Abbreviations:

mg: Miligram

ml: Milileter

inHg: Inch of Mercury

rpm: Rounds per minute

CFU: Colony forming unit

HCl: Hydrochloric acid

w/v: Weight/volume

HCl: hydrochloric acid

STD: Standard

Wt.: weight

O.P.A: Orthophosphoric acid