Ethambutol Tablets

General Notices

Action and use

Antituberculosis drug.

Definition

Ethambutol Tablets contain Ethambutol Hydrochloride.

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

Content of ethambutol hydrochloride, C10H24N2O2,2HCl

95.0 to 105.0% of the stated amount.

Identification

A. Extract a quantity of the powdered tablets containing 50 mg of ethambutol hydrochloride with 5 mL of methanol, filter and evaporate the filtrate to dryness. The infrared absorption spectrum of the residue, Appendix II A, is concordant with the reference spectrum of ethambutol hydrochloride (RS 134).
B. Shake a quantity of the powdered tablets containing 0.1 g of ethambutol hydrochloride with 10 mL of water, filter and add to the filtrate 2 mL of a 1% w/v solution of copper(ii) sulfate followed by 1 mL of 1m sodium hydroxide. A blue colour is produced.

2-Aminobutanol

Carry out the method for thin-layer chromatography, Appendix III A, using silica gel G as the coating substance and a mixture of 10 volumes of 13.5m ammonia, 15 volumes of water and 75 volumes of methanol as the mobile phase. Apply separately to the plate 2 µL of each of the following solutions. For solution (1) shake a quantity of the powdered tablets containing 0.50 g of ethambutol hydrochloride for 5 minutes with sufficient methanol to produce 10 mL. Solution (2) contains 0.050% w/v of 2-aminobutan-1-ol in methanol. After removal of the plate, allow it to dry in air, heat at 110° for 10 minutes, cool, spray with ninhydrin solution R1 and heat at 110° for 5 minutes. Any spot corresponding to 2-aminobutanol in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (2) (1%).

Assay

Weigh and powder 20 tablets. Add 20 mL of 2m sodium hydroxide to a quantity of the powdered tablets containing 0.2 g of ethambutol hydrochloride, mix with the aid of ultrasound for 5 minutes and extract with three successive 25 mL quantities of a mixture of 3 volumes of chloroform and 1 volume of propan-2-ol. Filter each extract successively through the same filter consisting of anhydrous sodium sulfate on an absorbent cotton plug moistened with a mixture of 3 volumes of chloroform and 1 volume of propan-2-ol and wash the plug with 10 mL of the same solvent mixture. Add 100 mL of anhydrous acetic acid to the combined extracts and washings and carry out Method I for non-aqueous titration, Appendix VIII A, using 1-naphtholbenzein solution as indicator. Each mL of 0.1m perchloric acid VS is equivalent to 13.86 mg of C10H24N2O2,2HCl.