Amoxapine Tablets

Amoxapine Tablets contain not less than 90.0 per cent and not more than 110.0 per cent of the stated amount of amoxapine, C₁₇H₁₆ClN₃O.

Usual strengths. 25 mg; 50 mg; 100 mg; 150 mg.

Identification

2. Triturate a quantity of powered tablets containing 50 mg of Amoxapine with 25-ml ofchloroformand filter. Evaporate to dryness on water bath. The residue complies with the following test. Determine by infrared absorption spectrophotometry (2.4.6). Compare the spectrum with that obtained with amoxapine RS or with the reference spectrum of amoxapine.
3. 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.

Tests

Dissolution (2.5.2).

Apparatus No. 1,

Medium. 900 ml of gastric juice, artificial (without pepsin) prepared by dissolving 2.0 g of sodium chloride in 80 ml of 1M hydrochloric acid and dilute to 1000 ml with water,

Speed and time. 50 rpm and 30 minutes.

Withdraw a suitable volume of the dissolution medium and filter. Measure the absorbance of the filtrate, suitably diluted with dissolution medium if necessary, at the maximum at about 294 nm (2.4.7). Calculate the content of C₁₇H₁₆ClN₃O in the medium from the absorbance obtained by repeating the determination using a solution of known concentration of amoxapine RS in dissolution medium.

1. Not less than 80 per cent of the stated amount ofC₁₇H₁₆ClN₃O.

Other tests. Comply with the tests stated under Tablets.

Assay. Determine by liquid chromatography (2.4.14).

Test solution. Weigh and powder 20 tablets. Weigh a quantity of the powder containing 50 mg of amoxapine add 25 ml of mobile phase and shake vigorously with the aid of ultrasound for 20 minutes and dilute to 50.0 ml with the mobile phase and filter. Dilute 5.0 ml of this solution to 50.0 ml with the mobile phase.

Reference solution. Dissolve a quantity of amoxapine RS in the acetonitrile to obtain a solution containing 0.1 per cent w/v of amoxapine. Dilute 5.0 ml of this solution to 50.0 ml with the mobile phase.

Chromatographic system

     –   a stainless steel column 25 cm x 4.6 mm, packed with octadecylsilane bonded to porous silica (5 µm),

       –   mobile phase:  Solution A:  a 0.138 per cent w/v solution of sodium dihydrogen orthophosphate,    monohydrate in  water,

               Solution B:  a 11.3 per cent w/v solution of tetramethylammonium chloride in water,                                                                                                                                                                             

            a mixture of 10 volumes of Solution B, 2.0 volumes of dilute ortho-phosphoric acid (1 in 5) and 360 volumes of acetonitrile and 628 volumes Solution A.

     –   flow rate: 1.5 ml per minute,

     –   spectrophotometer set at 254 nm,

     –   injection volume: 10 µl.

Inject the reference solution. The test is not valid unless the column efficiency is not less than 1200 theoretical plates, the tailing factor is not more than 1.8 and the relative standard deviation for replicate injections is not more than 2.0 per cent.

Inject the reference solution and the test solution.

Calculate the content of C₁₇H₁₆ClN₃O.

Storage. Store in tightly closed containers.