Aspirin and Caffeine Tablets

General Notices

Action and use

Salicylate; non-selective cyclo-oxygenase inhibitor; antipyretic; analgesic; anti-inflammatory.

Definition

Aspirin and Caffeine Tablets contain, in each, 350 mg of Aspirin and 30 mg of Caffeine.

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

Content of aspirin, C9H8O4

330 to 370 mg.

Content of caffeine, C8H10N4O2

27.5 to 32.5 mg.

Identification

A. Boil 1 g of the powdered tablets with 10 mL of 1m sodium hydroxide, cool and filter. Acidify the filtrate with 1m sulfuric acid; a white precipitate is produced. To a solution of the precipitate add iron(iii) chloride solution R1; a deep violet colour is produced.
B. Shake 0.5 g of the powdered tablets with 10 mL of water for 5 minutes, filter and add 10 mL of 1m sodium hydroxide. Extract with three 30 mL quantities of dichloromethane, washing each extract with the same 10 mL of water. Filter the combined extracts through absorbent cotton and evaporate the filtrate to dryness. Reserve a quantity of the residue for test C. Dissolve 10 mg of the residue in 1 mL of hydrochloric acid, add 0.1 g of potassium chlorate and evaporate to dryness in a porcelain dish. A reddish residue remains, which becomes purple on exposure to ammonia vapour.
C. The light absorption, Appendix II B, in the range 240 to 350 nm of a 0.001% w/v solution of the residue reserved in test B exhibits a maximum at 273 nm.

TESTS

Salicylic acid

To a quantity of the powdered tablets containing 0.50 g of Aspirin add 50 mL of dichloromethane and 10 mL of water, shake well and allow to separate. Filter the dichloromethane layer through a dry filter paper and evaporate 10 mL of the filtrate to dryness at room temperature using a rotary evaporator. To the residue add 4 mL of ethanol (96%), stir well, dilute to 100 mL with water at a temperature not exceeding 10°, filter immediately, rapidly transfer 50 mL to a Nessler cylinder, add 1 mL of freshly prepared ammonium iron(iii) sulfate solution R1, mix and allow to stand for 1 minute. Any violet colour produced is not more intense than that obtained by adding 1 mL of freshly prepared ammonium iron(iii) sulfate solution R1 to a mixture of 3 mL of a freshly prepared 0.050% w/v solution of salicylic acid in ethanol (96%) and sufficient water to produce 50 mL contained in a second Nessler cylinder (3.0%).

Dissolution

For aspirin

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 2, rotating the paddle at 50 revolutions per minute.
(b) Use 500 mL of a pH 4.5 buffer prepared by mixing 29.9 g of sodium acetate and 16.6 mL of glacial acetic acid with sufficient water to produce 10 litres, at a temperature of 37°, as the medium.
procedure
(1) After 45 minutes withdraw a 20 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 265 nm, Appendix II B, using dissolution medium in the reference cell.
(2) Measure the absorbance of a suitable solution of aspirin BPCRS in the dissolution medium using dissolution medium in the reference cell.
determination of content

Calculate the total content of aspirin, C9H8O4, in the medium from the absorbances obtained and using the declared content of C9H8O4 in aspirin BPCRS.

Assay

Weigh and powder 20 tablets.

For aspirin

To a quantity of the powder containing 0.7 g of Aspirin add 20 mL of water and 2 g of sodium citrate and boil under a reflux condenser for 30 minutes. Cool, wash the condenser with 30 mL of warm water and titrate with 0.5m sodium hydroxide VS using phenolphthalein solution R1 as indicator. Each mL of 0.5m sodium hydroxide VS is equivalent to 45.04 mg of C9H8O4.

For caffeine

To a quantity of the powder containing 30 mg of Caffeine add 200 mL of water and shake for 30 minutes. Add sufficient water to produce 250 mL and filter. To 10 mL of the filtrate add 10 mL of 1m sodium hydroxide and extract immediately with five 30 mL quantities of chloroform, washing each extract with the same 10 mL of water. Filter the combined chloroform extracts, if necessary, through absorbent cotton previously moistened with chloroform. Evaporate the solution to dryness and dissolve the residue as completely as possible in water, warming gently if necessary. Cool, add sufficient water to produce 100 mL, mix and filter if necessary. Measure the absorbance of the resulting solution at the maximum at 273 nm, Appendix II B. Calculate the content of C8H10N4O2 taking 504 as the value of A(1%, 1 cm) at the maximum at 273 nm.

Labelling

The label states that the tablets contain Aspirin, unless this word appears in the name of the tablets. This requirement does not apply in countries where exclusive proprietary rights in the name Aspirin are claimed.