Clonazepam

(Ph. Eur. monograph 0890)

C₁₅H₁₀ClN₃O₃    315.7    1622-61-3

Benzodiazepine.

Clonazepam Injection

Clonazepam Oral Suspension

Clonazepam Tablets

Ph Eur

5-(2-Chlorophenyl)-7-nitro-1,3-dihydro-2H-1,4-benzodiazepin-2-one.

99.0 per cent to 101.0 per cent (dried substance).

Slightly yellowish, crystalline powder.

Practically insoluble in water, slightly soluble in alcohol and in methanol.

About 239 °C.

Infrared absorption spectrophotometry (2.2.24).

Comparison   Ph. Eur. reference spectrum of clonazepam.

Liquid chromatography (2.2.29). Carry out the test protected from light and prepare the solutions immediately before use.

Solvent mixture  tetrahydrofuran R, methanol R, water R (10:42:48 V/V/V).

Test solution  Dissolve 0.100 g of the substance to be examined in methanol R and dilute to 20.0 mL with the same solvent. Dilute 1.0 mL to 10.0 mL with the solvent mixture.

Reference solution (a)  Dilute 1.0 mL of the test solution to 100.0 mL with the solvent mixture. Dilute 1.0 mL of the solution to 10.0 mL with the solvent mixture.

Reference solution (b)  Dissolve 5 mg of the substance to be examined and 5 mg of flunitrazepam R in the solvent mixture and dilute to 100.0 mL with the solvent mixture.

Reference solution (c)  Dissolve 1.0 mg of clonazepam impurity B CRS in the solvent mixture and dilute to 20.0 mL with the solvent mixture. Dilute 1.0 mL of the solution to 100.0 mL with the solvent mixture.

• — size: l = 0.15 m, Ø = 4.6 mm,

• — stationary phase: end-capped octylsilyl silica gel for chromatography R (5 µm).

Mobile phase  Mix 10 volumes of tetrahydrofuran R, 42 volumes of methanol R and 48 volumes of a 6.6 g/L solution of ammonium phosphate R previously adjusted to pH 8.0 with a 40 g/L solution of sodium hydroxide R or dilute phosphoric acid R.

Flow rate  1.0 mL/min.

Detection  Spectrophotometer at 254 nm.

Injection  10 µL.

Run time  3 times the retention time of clonazepam.

Relative retention  With reference to clonazepam (retention time = about 7 min): impurity B = about 2.1; impurity A = about 2.4.

System suitability  Reference solution (b):

• — resolution: minimum 1.8 between the peaks due to flunitrazepam and to clonazepam.

• — impurity A: not more than the area of the principal peak in the chromatogram obtained with reference solution (a) (0.1 per cent),

• — impurity B: not more than the area of the principal peak in the chromatogram obtained with reference solution (c) (0.1 per cent)

• — any other impurity: for each impurity, not more than the area of the principal peak in the chromatogram obtained with reference solution (a) (0.1 per cent),

• — total: not more than twice the area of the principal peak in the chromatogram obtained with reference solution (a) (0.2 per cent),

• — disregard limit: 0.5 times the area of the principal peak in the chromatogram obtained with reference solution (a) (0.05 per cent).

Maximum 0.5 per cent, determined on 1.000 g by drying in an oven at 105 °C for 4 h.

Maximum 0.1 per cent, determined on 1.0 g.

Dissolve 0.275 g in 50 mL of acetic anhydride R. Titrate with 0.1 M perchloric acid, determining the end-point potentiometrically (2.2.20).

1 mL of 0.1 M perchloric acid is equivalent to 31.57 mg of C₁₅H₁₀ClN₃O₃.

Protected from light.

Specified impurities  A, B.

A. (2-amino-5-nitrophenyl)(2-chlorophenyl)methanone,

B. 3-amino-4-(2-chlorophenyl)-6-nitroquinolin-2(1H)-one.

Ph Eur