Aspirin and Caffeine Tablets

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

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.

330  to 370  mg.

27.5  to 32.5  mg.

A.  Boil 1  g of the powdered tablets with 10  ml of 1m sodium hydroxide, cool and filter. Acidify the filtrate with 1m sulphuric 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.

To a quantity of the powdered tablets containing 0.50  g of Aspirin add 50  ml of chloroform and 10  ml of water, shake well and allow to separate. Filter the chloroform 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) sulphate 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) sulphate solution R1 to a mixture of 3  ml of a freshly prepared 0.050% w/v solution of salicylic acid, 2  ml of ethanol (96%) and sufficient water to produce 50  ml contained in a second Nessler cylinder (3.0%).

Comply with the requirements for Monographs of the British Pharmacopoeia in the dissolution test for tablets and capsules, Appendix XII B1, using Apparatus 2. Use as the medium 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 and rotate the paddle at 50 revolutions per minute. Withdraw a sample of 20  ml of the medium and filter. Immediately measure the absorbance of the filtrate, Appendix II B, diluted with the dissolution medium if necessary, at 265  nm using dissolution medium in the reference cell. Measure the absorbance of a suitable solution of aspirin BPCRS in the dissolution medium and calculate the total content of aspirin, C₉H₈O₄, in the medium using the declared content of C₉H₈O₄ in aspirin BPCRS.

Weigh and powder 20  tablets.

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.

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.

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.