Friday, 31 July 2009

Monographs: Pharmaceutical substances: Diazepamum - Diazepam


Molecular formula. C16H13ClN2O

Relative molecular mass. 284.7

Graphic formula.

Chemical name. 7-Chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one; CAS Reg. No. 439-14-5.

Description. A white or almost white, crystalline powder; odourless or almost odourless.

Solubility. Very slightly soluble in water; soluble in ethanol (~750 g/l) TS.

Category. Tranquillizer.

Storage. Diazepam should be kept in a well-closed container, protected from light.

Requirements

Definition. Diazepam contains not less than 99.0% and not more than 101.0% of C16H13ClN2O, calculated with reference to the dried substance.

Identity tests

• Either tests A and D or tests B, C and D may be applied.

• For tests B and C use low-actinic glassware and measure within 30 minutes.

A. Carry out the examination as described under 1.7 Spectrophotometry in the infrared region. The infrared absorption spectrum is concordant with the reference spectrum of diazepam.

B. The absorption spectrum of an 8.0 μg/ml solution in hydrochloric acid (0.1 mol/l) VS, when observed between 230 nm and 350 nm, exhibits maxima at about 241 nm and 286 nm; the absorbances of a 1-cm layer at the maximum wavelengths of 241 nm and 286 nm are about 0.80 and 0.38, respectively (preferably use 2-cm cells for the measurements and calculate the absorbances for 1-cm layers).

C. The absorption spectrum of a 0.030 mg/ml solution in hydrochloric acid (0.1 mol/l) VS, when observed between 325 nm and 400 nm, exhibits a maximum at about 362 nm; the absorbance of a 1-cm layer at this wavelength is about 0.44 (preferably use 2-cm cells for the measurement and calculate the absorbance of a 1-cm layer).

D. Carry out the combustion as described under 2.4 Oxygen flask method, using 20 mg of the test substance and 5 ml of sodium hydroxide (~80 g/l) TS as the absorbing liquid. When the process is complete, acidify with sulfuric acid (~100 g/l) TS and boil gently for 2 minutes; the solution yields reaction A, described under 2.1 General identification tests as characteristic of chlorides.

Melting range. 131-135°C.

Heavy metals. Use 1.0 g for the preparation of the test solution as described under 2.2.3 Limit test for heavy metals, Procedure 3; determine the heavy metals content according to Method A; not more than 20 μg/g.

Sulfated ash. Not more than 1.0 mg/g.

Loss on drying. Dry to constant weight at 50°C under reduced pressure (not exceeding 0.6 kPa or about 5 mm of mercury); it loses not more than 5.0 mg/g.

Related substances. Carry out the test in subdued light as described under 1.14.1 Thin-layer chromatography, using silical gel R2 as the coating substance and a mixture of 1 volume of dehydrated ethanol R and 24 volumes of ethyl acetate R as the mobile phase. Apply separately to the plate 10 μl of each of 2 freshly prepared solutions in chloroform R containing (A) 0.20 g of the test substance per ml and (B) 0.10 mg of 5-chloro-2-methylaminobenzophenone RS per ml. After removing the plate from the chromatographic chamber, allow it to dry in air, and examine the chromatogram in ultraviolet light (254 nm). Any spot obtained with solution A, other than the principal spot, is not more intense than that obtained with solution B.

Assay. Dissolve about 0.55 g, accurately weighed, in 30 ml of glacial acetic acid R1, and titrate with perchloric acid (0.1 mol/l) VS, determining the end-point potentiometrically as described under 2.6 Non-aqueous titration, Method A. Each ml of perchloric acid (0.1 mol/l) VS is equivalent to 28.47 mg of C16H13ClN2O.

Additional requirements for Diazepam for parenteral use

Complies with the monograph for "Parenteral preparations".

Bacterial endotoxins. Carry out the test as described under 3.4 Test for bacterial endotoxins; contains not more than 11.6 IU of endotoxin RS per mg.

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