Phenoxymethylpenicillin Tablets

General Notices

Action and use

Penicillin antibacterial.

Definition

Phenoxymethylpenicillin Tablets contain Phenoxymethylpenicillin Potassium.

The tablets comply with the requirements stated under Tablets and with the following requirements.

Content of phenoxymethylpenicillin, C16H18N205S, calculated as the sum of the contents of phenoxymethylpenicillin and 4-hydroxyphenoxymethylpenicillin

92.5 to 107.5% of the stated amount of phenoxymethylpenicillin.

Identification

A. Shake a quantity of the powdered tablets containing the equivalent of 80 mg of phenoxymethylpenicillin with water, dilute to 250 mL with water and filter. The light absorption of the filtrate, Appendix II B, exhibits maxima at 268 nm and 274 nm and a minimum at 272 nm.
B. Shake a quantity of the powdered tablets containing the equivalent of 10 mg of phenoxymethylpenicillin with 10 mL of water, filter and add 0.5 mL of neutral red solution. Add sufficient 0.01m sodium hydroxide to produce a permanent orange colour and then add 1.0 mL of penicillinase solution. The colour changes rapidly to red.
C. Ignite 0.5 g of the powdered tablets, add 5 mL of 2m hydrochloric acid, boil, cool and filter. The filtrate yields reaction B characteristic of potassium salts, Appendix VI.

Tests

Dissolution

Comply with the requirements for Monographs of the British Pharmacopoeia in the dissolution test for tablets and capsules, Appendix XII B1.

test conditions
(a) Use Apparatus 1, rotating the basket at 100 revolutions per minute.
(b) Use 900 mL of a 0.68% w/v solution of potassium dihydrogen orthophosphate, adjusted to pH 6.8 by the addition of 1m sodium hydroxide, at a temperature of 37°, as the medium.
procedure
(1) After 45 minutes withdraw a 10 mL sample of the medium and measure the absorbance of the filtered sample, suitably diluted with the dissolution medium if necessary, at the maximum at 268 nm, Appendix II B, using dissolution medium in the reference cell.
(2) Measure the absorbance of a suitable solution of phenoxymethylpenicillin potassium BPCRS in dissolution medium using dissolution medium in the reference cell.
determination of content

Calculate the total content of phenoxymethylpenicillin, C16H18N2O5S, in the medium from the absorbances obtained and from the declared content of C16H18N2O5S in phenoxymethylpenicillin potassium BPCRS.

Assay

Weigh and powder 20 tablets. Shake a quantity of the powder containing the equivalent of 0.125 g of phenoxymethylpenicillin with 300 mL of water for 30 minutes, add sufficient water to produce 500 mL, dilute 25 mL to 100 mL with water and filter. Place two 2-mL aliquots of the filtrate in separate stoppered tubes. To one tube add 10 mL of imidazole-mercury reagent, mix, stopper the tube and immerse in a water bath at 60° for exactly 25 minutes, swirling occasionally. Remove from the water bath and cool rapidly to 20° (solution A). To the second tube add 10 mL of water and mix (solution B). Without delay measure the absorbances of solutions A and B at the maximum at 325 nm, Appendix II B, using in the reference cell a mixture of 2 mL of water and 10 mL of imidazole-mercury reagent for solution A and water for solution B. Calculate the content of C16H18N2O5S from the difference between the absorbances of solutions A and B, from the difference obtained by repeating the operation using 0.14 g of phenoxymethylpenicillin potassium BPCRS in place of the preparation being examined and from the declared content of C16H18N2O5S in phenoxymethylpenicillin potassium BPCRS.

Labelling

The quantity of active ingredient is stated in terms of the equivalent amount of phenoxymethylpenicillin.