Carbimazole Tablets

General Notices

Action and use

Thionamide antithyroid drug.

Definition

Carbimazole Tablets contain Carbimazole.

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

Content of carbimazole, C7H10N2O2S

90.0 to 110.0% of the stated amount.

Identification

Extract a quantity of the powdered tablets containing 50 mg of Carbimazole with two 5-mL quantities of dichloromethane. Combine the dichloromethane extracts, filter and evaporate the filtrate to dryness. The infrared absorption spectrum, Appendix II A, of the residue after drying at 60° at a pressure not exceeding 0.7 kPa for 30 minutes is concordant with the reference spectrum of carbimazole (RS 042).

Thiamazole and other related substances

Carry out the test protected from light and prepare the solutions immediately before use.

Carry out the method for liquid chromatography, Appendix III D, using the following solutions.

(1) Disperse a quantity of the powdered tablets containing 20 mg of Carbimazole in 10 mL of acetonitrile with the aid of ultrasound for 5 minutes, filter through a nylon syringe, filter and dilute 1 volume of the filtrate to 20 volumes with water.
(2) Dilute 1 volume of solution (1) to 200 volumes with mobile phase A.
(3) 0.0001% w/v of thiamazole in mobile phase A.
(4) 0.002% w/v of carbimazole BPCRS and 0.0001% w/v of thiamazole in mobile phase A.
chromatographic conditions
(a) Use a stainless steel column (15 cm × 3.9 mm) packed with base-deactivated octadecylsilyl silica gel for chromatography (5 µm) (Waters Symmetry C18 is suitable).
(b) Use gradient elution and the mobile phase described below.
(c) Use a flow rate of 1 mL per minute.
(d) Use an ambient column temperature.
(e) Use a detection wavelength of 254 nm.
(f) Inject 100 µL of each solution.
mobile phase

Mobile phase A5 volumes of acetonitrile and 95 volumes of water.

Mobile phase B20 volumes of acetonitrile and 80 volumes of water.

system suitability

The test is not valid unless, in the chromatogram obtained with solution (4), the resolution between the peaks due to carbimazole and thiamazole is at least 5.0.

limits

In the chromatogram obtained with solution (1):

the area of any peak corresponding to thiamazole is not greater than the area of the principal peak in the chromatogram obtained with solution (3) (1%);

the area of any other secondary peak is not greater than the area of the principal peak in the chromatogram obtained with solution (2) (0.5%).

Assay

Carry out the test protected from light and prepare the solutions immediately before use.

Weigh and powder 20 tablets. Carry out the method for liquid chromatography, Appendix III D, using the following solutions.

(1) Disperse a quantity of the powdered tablets containing 20 mg of Carbimazole in 10 mL of acetonitrile with the aid of ultrasound for 5 minutes, filter through a nylon syringe filter and dilute 1 volume of this solution to 40 volumes with a 5% v/v solution of acetonitrile.
(2) 0.005% w/v of carbimazole BPCRS in mobile phase A.
(3) 0.01% w/v of carbimazole BPCRS and 0.0005% w/v of thiamazole in mobile phase A.
chromatographic conditions

The chromatographic procedure described under Related substances may be used.

system suitability

The test is not valid unless, in the chromatogram obtained with solution (3), the resolution between the peaks due to carbimazole and thiamazole is at least 5.0.

determination of content

Calculate the content of C7H10N2O2S in the tablets using the declared content of C7H10N2O2S in carbimazole BPCRS.

IMPURITIES

The impurities limited by the requirements of this monograph include those listed under Carbimazole.