1.0) Description: Visual

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

Average weight (mg) =   wt of 20 tablets (gm) x 1000


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:

Deviation (%) =  Weight of each tablet – Average weight    x 100

Average weight

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

4.0)      Identification Test:

Extract a quantity of the powdered tablets containing about 0.2 g of Dothiepin HCl with 20 ml of dichloromethane, centrifuge, filter through anhydrous sodium sulphate and evaporate the filtrate to dryness. Dissolve the residue in the minimum quantity of ethanol and add an excess of ether. Filter the precipitation, wash with ether and dry. The residue complies with the following tests.

Determine by infrared absorption spectrophotometry. Compare the spectrum with that obtained with Dothiepin HCl reference standard or with the reference spectrum of Dothiepin HCl.

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.


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:

Diameter and thickness are determined by vernier calliper in mm.

8.0)      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.

9.0)      Related substances: Determine by thin layer chromatography, coating the plate with silica gel GF254.

            Mobile phase: A mixture of 1 volume of 13.5 M ammonia, 10 volumes of 2- propranolol and 90 volumes of 1, 2-dichloroethane.

            Test solution: Disperse a quantity of the powdered tablets containing 0.25 g of Dothiepin HCl with 5 ml of dichloromethane, centrifuge and use the clear supernatant liquid.                                                               Reference solution (a): A 0.08 per cent w/v solution of Ivermectin reference standard in methanol.

            Reference solution (a): Dilute 2 ml of the test solution to 5 ml with dichloromethane.

Reference solution (b): A solution containing 0.010 per cent w/v each of 3-(dibenzo[b,e]thiepin-11(6H)-ylidene)-N, N-dimethylaminopropan-1-amine S-oxide HCl reference standard and 3-(dibenzo[b,e]thiepin-11(6H)-one reference standard in chloroform.

            Apply to the plate 5µl of each solution. Allow the mobile phase to rise about three-fourths of the height of the plate. Dry the plate in air and examine under ultraviolet light at 254nm. In the chromatogram obtained with reference solution (b) the spot with the lower Rvalue is more intense than any corresponding spot in the chromatogram obtained with the reference solution (a) (0.5 per cent). In the chromatogram obtained with test solution, any secondary spot other than any spot corresponding to the spot with lower Rvalue in the chromatogram obtained with reference solution  (b) is not more intense than the proximate spot in the chromatogram obtained with reference solution (b) (0.2 per cent).

10.0)    Z-impurity: Determine by gas chromatography.

            Test solution: Disperse a quantity of tablet powder containing 25 mg of the Dothiepin HCl in 5 ml of methanol for 15 minutes, centrifuge and use the supernatant liquid.

            Reference solution: A 0.5 per cent w/v solution of Dothiepin HCl reference standard in methanol.

            Chromatography System:

  • A glass column 1.8 m x 3 mm, packed with acid-washed, silanised distomaceous support (100 to 120 mesh) coated with 3 per cent w/w of cyanopropylmethyl phenyl methyl silicone fluid (such as OV-225),
  • Temperature

Column: 200°

Inlet port: 260°

  • Flame ionization detector,
  • Nitrogen as the carrier gas,
  • Injection volume: 1 µl

In the chromatogram obtained with the reference solution a peak due to Z-Dothiepin is present with a retention time of approximately 0.83 retention time of the principal peak which is due to E-Dothiepin. In the chromatogram obtained with the test solution the area of any peak corresponding to Z-Dothiepin is not more than 7.5 per cent of the sum of the areas of the peaks due to Z-Dothiepin and E- Dothiepin.

11.0)    Assay: Determined by liquid chromatography.

Test solution: Weigh and powder 20 tablets. Disperse a quantity of the powder containing 50 mg of Dothiepin HCl with about 70 ml of 0.1 M HCl, shake for about 30 minutes and dilute to 100 ml with 0.1 M HCl and filter, rejecting the first few ml of filtrate, Dilute 25 ml of this solution to 100 ml with 0.1 M HCl.

Reference solution: A 0.0125 per cent w/v solution of Dothiepin HCl reference standard in 0.1 M HCl.

            Chromatographic system:

  • A stainless steel column 25 cm X 4.6 mm, packed with octadecylsilane bonded to porous silica (5µm)
  • Mobile Phase: a mixture of 10 volumes of tetrahydrofuran, 40 volumes of acetonitrile, and 50 volumes of 0.5 per cent w/v solution of potassium dihydrogen orthophosphate adjusted to pH 3.0 with 2M O.P.A.
  • Flow rate: 1.5 ml per minute,
  • Spectrophotometer set at 231 nm,
  • Injection volume: 20 µl

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

Inject reference solution and the test solution.

Calculate the content of Dothiepin HCl in the tablet.


Area of Test      STD Wt.(mg)    25            100               50      Potency

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

Area of STD        100                 100     Test Wt.(mg)      5          100


Additional method: by UV Spectrophotometer

Test Solution: Weigh and powder 20 tablets. Weight sample equivalent to 25 mg of Dothiepin 100 ml volumetric flask add 20 ml 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 5 ml of this solution to 25 ml in 0.1 M HCl.

Reference Solution: Weigh 25 mg of reference standard of Dothiepin in 100 ml of volumetric flask. Add 20 ml 0.1 M HCl into it and sonicate to dissolve. Make up to mark with 0.1 M HCl. Dilute 5 ml of this solution to 25 ml with 0.1 M HCl.

Check Absorbance of test as well as reference standard at about 303 nm in UV Spectrophotometer.

Calculate the content of Dothiepin in the tablets.


Abs. of Test      STD Wt.(mg)  5            100               25      Potency

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

Abs. of STD        100               25     Test Wt.(mg)      5          100


            Acceptance criteria: 95.0%-105.0%


            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



Wt.: Weight                                          HCl: Hydrochloric Acid

mg: Milligram                                       O.P.A.: Orthophosphoric Acid

ml: Milliliter                                          CFU: Colony Forming Unit

STD: Standard                                                 w/v: Weight/Volume

inHg: Inch of Mercury                                     Abs. Absorbance

rpm: Rotations Per Minute