Benorilate Tablets

General Notices

Action and use

Salicylate-paracetamol derivative; antipyretic; analgesic; anti-inflammatory.

Definition

Benorilate Tablets contain Benorilate.

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

Content of benorilate, C17H15NO5

95.0 to 105.0% of the stated amount.

Identification

Shake a quantity of the powdered tablets containing 1 g of Benorilate with 30 mL of a mixture of 9 volumes of chloroform and 1 volume of methanol for 10 minutes, filter and evaporate the filtrate to dryness. The residue complies with the following tests.

A. The infrared absorption spectrum, Appendix II A, is concordant with the reference spectrum of benorilate (RS 023).
B. To 10 mg add 10 mL of 6m hydrochloric acid and boil until completely dissolved. To 5 mL of the resulting solution add 0.1 mL of strong 1-naphthol solution, mix and add sufficient 1m sodium hydroxide to make the solution just alkaline. A blue colour is produced which can be extracted into butan-1-ol.
C. Melting point, about 179°, Appendix V A.

TESTS

4-Aminophenol

Shake a quantity of the powdered tablets containing 2.5 g of Benorilate with 100 mL of water for 15 minutes and filter. If the filtrate is opalescent, warm on a water bath until it becomes clear and allow to cool. To 20 mL of the filtrate add 0.2 mL of sodium nitroprusside-carbonate solution, mix and allow to stand for 30 minutes. The solution is not more intensely coloured than a solution prepared at the same time and in the same manner but using 2 mL of a solution of 4-aminophenol containing 5 µg per mL and 18 mL of water in place of the filtrate (20 ppm).

Salicylic acid

Shake a quantity of the powdered tablets containing 0.50 g of Benorilate with 100 mL of water for 15 minutes and filter. If the filtrate is opalescent, warm on a water bath until it becomes clear and allow to cool. Transfer 10 mL of the filtrate to a Nessler cylinder, dilute to 50 mL with water, add 0.2 mL of a 0.5% w/v solution of iron(iii) chloride and allow to stand for 1 minute. The colour obtained is not more intense than that of a solution prepared at the same time by adding 0.2 mL of a 0.5% w/v solution of iron(iii) chloride to a mixture of 1 mL of a 0.025% w/v solution of salicylic acid in ethanol (96%) and sufficient water to produce 50 mL (0.5%).

Related substances

Carry out the method for thin-layer chromatography, Appendix III A, using a silica gel HF254 precoated plate (Analtech plates are suitable) and a mixture of 5 volumes of glacial acetic acid, 15 volumes of ether and 80 volumes of dichloromethane as the mobile phase. Apply separately to the plate 10 µL of each of the following solutions. Solution (1) contains 4.0% w/v of the residue obtained in the tests for Identification in a mixture of 9 volumes of chloroform and 1 volume of methanol. For solution (2) dilute 1 volume of solution (1) to 100 volumes with a mixture of 9 volumes of chloroform and 1 volume of methanol. For solution (3) dilute 1 volume of solution (1) to 500 volumes with a mixture of 9 volumes of chloroform and 1 volume of methanol. Solution (4) contains 0.0080% w/v of paracetamol in a mixture of 9 volumes of chloroform and 1 volume of methanol. After removal of the plate, allow it to dry in air and develop in a second mobile phase consisting of a mixture of 10 volumes of formic acid, 45 volumes of ether and 45 volumes of 2,2,4-trimethylpentane. After removal of the plate, allow it to dry in air and examine under ultraviolet light (254 nm).

Any spot corresponding to paracetamol in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (4) (0.2%). Any secondary spot in the chromatogram obtained with solution (1) with an Rf value slightly higher than that of the principal spot is not more intense than the principal spot in the chromatogram obtained with solution (2) (1%). Any other secondary spot in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (3) (0.2%).

Assay

Weigh and powder 20 tablets. Shake a quantity of the powder containing 0.1 g of Benorilate with 100 mL of absolute ethanol for 30 minutes and filter. Dilute 5 mL of the filtrate to 250 mL with absolute ethanol and measure the absorbance of the resulting solution at the maximum at 240 nm, Appendix II B. Calculate the content of C17H15NO5 taking 740 as the value of A(1%, 1 cm) at the maximum at 240 nm.