Monographs: Pharmaceutical substances: Dacarbazinum - Dacarbazine

Monographs: Pharmaceutical substances: Dacarbazinum - Dacarbazine

C₆H₁₀N₆O

Relative molecular mass. 182.2

Chemical name. 5-(3,3-Dimethyl-1-triazeno)imidazole-4-carboxamide; 5-(3,3-dimethyl-1-triazenyl)-1H-imidazole-4-carboxamide; CAS Reg. No. 4342-03-4.

Description. A colourless or pale yellow, crystalline powder.

Solubility. Slightly soluble in water and ethanol (~750 g/l) TS.

Category. Cytotoxic drug.

Storage. Dacarbazine should be kept in a tightly closed container, protected from light, and stored at a temperature not exceeding 8 °C.

Additional information. CAUTION: Dacarbazine must be handled with care, avoiding contact with the skin and inhalation of airborne particles.

Requirements

Dacarbazine contains not less than 97.0% and not more than 102.0% of C₆H₁₀N₆O, calculated with reference to the dried substance.

Identity tests

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

A. Carry out the examination as described under 1.7 Spectrophotometry in the infrared region. The infrared absorption spectrum is concordant with the spectrum obtained from dacarbazine RS or with the reference spectrum of dacarbazine.

B. The absorption spectrum of a 6μg/ml solution in hydrochloric acid (0.1mol/l) VS, when observed between 230nm and 350nm, exhibits a maximum at about 323nm and a pronounced shoulder at 275nm. The absorbance of a 1-cm layer at the maximum wavelength of 323 nm is about 0.64.

C. Dissolve 25 mg in 5 ml of water, add 1 drop of cobalt(II) chloride (30 g/l) TS and 1 drop of ammonia (~100 g/l) TS; a violet-red solution is produced.

D. Dissolve 25mg in 5ml of hydrochloric acid (~70 g/l) TS, add about 0.2 g of zinc R powder and allow to stand for 5 minutes. Filter, and to the filtrate add 3 drops of sodium nitrite (10 g/l) TS and 0.5ml of ammonium sulfamate (5 g/l) TS. After the reaction has subsided add 5 drops of N-(1-naphthyl)ethylenediamine hydrochloride/ethanol TS; a deep red solution is produced.

Clarity and colour of solution. A solution of 0.20 g in 10 ml of citric acid (20 g/l) TS is clear and not more intensely coloured than standard colour solution Yw2 when compared as described under 1.11 Colour of liquids.

Sulfated ash. Not more than 1.0 mg/g.

Loss on drying. Dry at 60 °C to constant mass under reduced pressure (not exceeding 0.6 kPa or about 5 mm of mercury); it loses not more than 5 mg/g.

Related substances. Carry out the test as described under 1.14.1 Thin-layer chromatography, using silica gel R2 as the coating substance and 5 volumes of 1-butanol R, 2 volumes of water and 1 volume of acetic acid (~300 g/l) TS as the mobile phase. Apply separately to the plate 5μl of each of the 3 following solutions in methanol R containing (A) 0.04 g of Dacarbazine per ml, (B) 0.4 mg of dacarbazine related compound A RS per ml, and (C) 0.4 mg of dacarbazine related compound B 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 or greater in size than that obtained with solution B (1%) and solution C (1%).

Assay

• The solutions must be protected from light throughout the assay.

Dissolve about 30 mg, accurately weighed, in sufficient hydrochloric acid (0.1 mol/l) VS to produce 50 ml of stock solution. For solution S₁ dilute 1.0ml of the stock solution to 100 ml with hydrochloric acid (0.1 mol/l) VS. For solution S₂ dilute a further 1.0 ml aliquot of the stock solution to 100ml with phosphate buffer, pH 7.0, TS. Measure the absorbance of a 1-cm layer of solution S₁ at the maximum at about 323nm against a solvent cell containing hydrochloric acid (0.1 mol/l) VS. Measure the absorbance of a 1-cm layer of solution S₂ at the maximum at about 329nm against a solvent cell containing phosphate buffer, pH 7.0, TS. Calculate the percentage content of C₆H₁₀N₆O.