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Category Muscle relaxant.

      Tolperisone Hydrochloride contains not less than 98.5 per cent of C₁₆H₂₃NO.HCl, calculated on the dried basis.

Description White, crystalline powder; odour, slight, characteristic; hygroscopic.

Solubility Freely soluble in water and in ethanol; very soluble in acetic acid; soluble in acetic anhydride; slightly soluble in acetone; practically insoluble in ether.

Stability It is hygroscopic.

Contra-indication It is contra-indicated in myasthenia gravis.

Warning

      1. It may cause muscular weakness, headache, hypotension, nausea, vomiting, abdominal discomfort and anaphylactic reactions.

      2. Risk-benefit should be considered if it is to be used in pregnant women.

Packaging and storage Tolperisone Hydrochloride shall be kept in well-closed containers.

Identification

      A. Dissolve 200 mg in 2 ml of ethanol, add 2 ml of 1,3-dinitrobenzene TS and 2 ml of sodium hydroxide TS, and heat: a red colour develops.

      B. To 5 ml of a 5 per cent w/v solution of the test substance add 2 to 3 drops of iodine TS: a red-brown precipitate is produced.

      C. It yields the reactions characteristic of chlorides (Appendix 5.1).

Melting range 167º to 174º (Appendix 4.3).

Clarity and colour of solution A 10.0 per cent w/v solution is clear (Appendix 4.11) and colourless.

pH 4.5 to 5.5, in a 5.0 per cent w/v solution (Appendix 4.11).

Absorbance Dissolve 5.0 mg (after drying) in ethanol and dilute to 500.0 ml with the same solvent. The light absorption spectrum of the diluted solution, when observed between 220 nm and 350 nm, exhibits a maximum at about 257 nm; the specific absorbance at the maximum is 555 to 585 (Appendix 2.2).

Loss on drying Not more than 0.5 per cent w/w after drying over self-indicating silica gel in vacuum for 3 hours (Appendix 4.15).

Sulfated ash Not more than 0.1 per cent w/w (Appendix 5.3).

Sulfate Not more than 0.005 per cent w/w (Appendix 5.2). A 4.0-g sample shows no more sulfate than that corresponds to 0.20 ml of 0.010 M sulfuric acid.

Heavy metals Not more than 20 ppm (Method II, Appendix 5.2). Use 1.0 g; for the Standard Preparation, use 2 ml of lead standard solution (10 ppm Pb).

Piperidine hydrochloride Not more than 0.1 per cent w/w. Carry out the test as described in the “Ultraviolet and Visible Spectrophotometry” (Appendix 2.2). Transfer 200.0 mg of the test substance in a 10-ml volumetric flask. Add water to dissolve and dilute to volume. Use this solution as the test solution. Separately, dissolve 20.0 mg of piperidine hydrochloride in water to make 1000.0 ml and use this solution as the standard solution. Transfer 5.0 ml each of the test solution and the standard solution to different separators. Add 0.1 ml each of a 5 per cent w/v solution of copper(Il) sulfate, then add 0.1 ml each of strong ammonia solution and 10.0 ml each of a mixture of 3 volumes of 2,2,4-trimethylpentane and 1 volume of carbon disulfide, and shake vigorously for 30 minutes. Immediately after allowing to stand, separate the pentane-carbon disulfide mixture layer, and dehydrate with anhydrous sodium sulfate: the absorbance of the test solution at 438 nm is not more than that of the standard solution.

Assay Dissolve about 500 mg of Tolperisone Hydrochloride, accurately weighed, in 100 ml of anhydrous glacial acetic acid. Titrate with 0.1 M perchloric acid VS, determining the end-point potentiometrically (Appendix 6.1). Perform a blank determination, and make any necessary correction. Each ml of 0.1 M perchloric acid is equivalent to 28.18 mg of C₁₆H₂₃NO.HCl.