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AMOXICILLIN

Amoxycillin Trihydrate

Category Antibacterial.

          Amoxicillin contains not less than 90.0 per cent and not more than 105.0 per cent of C16H19N3O5S, calculated on the anhydrous basis.

          Description White or almost white, crystalline powder.

Solubility Slightly soluble in water, in ethanol, and in methanol; practically insoluble in chloroform, in ether, and in fixed oils.

Contra-indication; Warning; Precaution; Additional Information See under Penicillin V Potassium, p. 140.

Identification
          A. The infrared absorption spectrum is concordant with the spectrum obtained from Amoxicillin RS (Appendix 2.1) or with the reference spectrum of Amoxicillin.
          B. The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.
          C. Suspend 10 mg in 1 ml of water and add 2 ml of a mixture of 2 ml of potassium cupric-tartrate TS and 6 ml of water: a magenta colour is immediately produced.
          D. Dissolve 2 drops of aniline in a mixture of 1 ml of hydrochloric acid and 3 ml of water. Cool the solution in ice and add 1 ml of a freshly prepared 20 per cent w/v solution of sodium nitrite. Add the resulting mixture dropwise to a cold solution of 100 mg of the test substance in 2 ml of 5 M sodium hydroxide: the solution becomes deep cherry-red and a copious dark brown precipitate is produced.

Pakaging and storage Amoxicillin shall be kept in tightly closed containers and stored at a temperature not exceeding 25º.

Labelling The label on the container states storage condition.

Clarity of solution Dissolve 1.0 g in 10 ml of 0.5 M hydrochloric acid. Dissolve separately 1.0 g in 10 ml of diluted ammonia prepared by diluting 14 g of strong ammonia solution to 100 ml with water. (Note The solution contains not less than 3.3 per cent and not more than 3.5 per cent of NH3 (about 2 M).) Immediately after dissolution, the solutions are not more opalescent than reference suspension II (Appendix 4.1).

Crystallinity It is crystalline (Method I, Appendix 4.14).

pH 3.5 to 6.0, in a 0.2 per cent w/v solution (Appendix 4.11).

Specific rotation +290º to +315º, calculated on the anhydrous basis, determined in a 0.2 per cent w/v solution (Appendix 4.8).

Water Not less than 11.5 per cent w/w and not more than 14.5 per cent w/w (Karl Fischer Method, Appendix 4.12).

Dimethylaniline Not more than 20 ppm. Carry out the determination as described in the “Gas Chromatography” (Appendix 3.4).

          Internal standard solution Dissolve 50 mg of naphthalene in cyclohexane and dilute to 50 ml with the same solvent. Dilute 5 ml of this solution to 100 ml with cyclohexane.

          Standard solution To 50.0 mg of N,N-dimethylaniline add 2 ml of hydrochloric acid and 20 ml of water, shake to dissolve and dilute to 50.0 ml with water. Dilute 5.0 ml of this solution to 250.0 ml with water. To 1.0 ml of the latter solution in a ground-glass-stoppered tube add 5 ml of 1 M sodium hydroxide and 1.0 ml of Internal standard solution. Stopper the tube and shake vigorously for 1 minute. Centrifuge if necessary and use the upper layer.

          Test solution To 1.00 g of the substance to be examined in a ground-glass-stoppered tube add 5 ml of 1 M sodium hydroxide and 1.0 ml of Internal standard solution. Stopper the tube and shake vigorously for 1 minute. Centrifuge if necessary and use the upper layer.

          Chromatographic system The chromatographic procedure may be carried out using (a) a glass column 2 m long and 2 mm in internal diameter packed with silanized diatomaceous support impregnated with 3 per cent w/w of polymethylphenylsiloxane, (b) nitrogen as the carrier gas at a flow rate of about 30 ml per minute, and (c) a flame-ionization detector, maintaining the tempera-ture of the column at 120º and that of the injection port and of the detector at 150º.
          Procedure Inject 1 μl of Test solution and 1 μl of Standard solution.

Assay Carry out the determination as described in the “High-pressure Liquid Chromatography” (Appendix 3.5).

          Diluent Dissolve 13.6 g of potassium dihydrogen phosphate in water to make 2000 ml of solution, and adjust with a 45 per cent w/w solution of potassium hydroxide to a pH of 5.0±0.1. Mobile phase Prepare a mixture of 4 volumes of acetonitrile and 96 volumes of Diluent. Make adjustments if necessary. Decrease the acetonitrile concentration to increase the retention time of amoxicillin.

          Mobile phase Prepare a mixture of 4 volumes of acetonitrile and 96 volumes of Diluent. Make adjustments if necessary. Decrease the acetonitrile concentration to increase the retention time of amoxicillin.
          Standard preparation Dissolve an accurately weighed quantity of Amoxicillin RS, quantitatively in Diluent to obtain a solution having a known concentration of about 1.2 mg per ml. Use this solution within  8 hours.
          Assay preparation Transfer about 240 mg of Amoxicillin, accurately weighed, to a 200-ml volumetric flask, dissolve in and dilute with Diluent to volume, and mix. Use this solution within 6 hours.
          Chromatographic system The chromatographic procedure may be carried out using (a) a stainless steel column (25 cm × 4 mm) packed with octadecylsilane chemically bonded to porous silica or ceramic microparticle(3 to 10 μm), (b) Mobile phase at a flow rate of about 1.5 ml per minute, and (c) an ultraviolet photometer set at 230 nm.
          To determine the suitability of the chromatographic system, chromatograph Standard preparation, and record the peak responses as directed under Procedure: the relative standard deviation for replicate injections is not more than 2.0 per cent. The capacity factor, K’, is between 1.1 and 2.8, and the symmetry factor for the amoxicillin peak is not more than 2.5.
          Procedure Separately inject equal volumes (about 10 μl) of Standard preparation and Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks.

          Calculation Calculate the content of C16H19N3O5S in the Amoxicillin taken, using the declared content of C16H19N3O5S in Amoxicillin RS.

MONOGRAPHS • AMOXICILLIN
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หมายเหตุ / Note : TP II 2011 PAGE 24 - 25