Carbamazepine Tablets

General Notices

Carbamazepine Tablets from different manufacturers, whilst complying with the requirements of the monograph, are not interchangeable.

Action and use

Antiepileptic.

Definition

Carbamazepine Tablets contain Carbamazepine.

Production

A suitable dissolution test is carried out to demonstrate the appropriate release of Carbamazepine. The dissolution profile reflects the in vivo performance which in turn is compatible with the dosage schedule recommended by the manufacturer.

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

Content of carbamazepine, C₁₅H₁₂N₂O

95.0 to 105.0% of the stated amount.

Identification

Boil a quantity of the powdered tablets containing 0.2 g of Carbamazepine with 15 mL of acetone, filter the hot solution, wash the filtrate with two 5-mL quantities of hot acetone, cool in ice and evaporate the combined filtrates to dryness. The infrared absorption spectrum of the crystals, Appendix II A, is concordant with the reference spectrum of carbamazepine (RS 406).

TESTS

Related substances

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

(1) Shake a quantity of the powdered tablets containing 0.3 g of Carbamazepine with 100 mL of methanol for 15 minutes. Dilute to 200 mL with water, mix and filter.

(2) Dilute 1 volume of solution (1) to 500 volumes with methanol (50%).

(3) Dissolve 7.5 mg each of carbamazepine BPCRS and carbamazepine impurity A EPCRS in methanol and dilute to 100 mL with the same solvent. Dilute 1.0 mL of the resulting solution to 50 mL with methanol (50%).

chromatographic conditions

(a) Use a stainless steel column (25 cm × 4.6 mm) packed with nitrile silica gel for chromatography (10 µm) (Nucleosil 10 CN is suitable).

(b) Use isocratic elution and the mobile phase described below.

(d) Use an ambient column temperature.

(e) Use a detection wavelength of 230 nm.

(f) Inject 20 µL of each solution.

mobile phase

30 volumes of tetrahydrofuran, 120 volumes of methanol and 850 volumes of water, adding 0.2 volume of anhydrous formic acid and 0.5 volume of triethylamine to 1000 volumes of the solution.

system suitability

The test is not valid unless, in the chromatogram obtained with solution (3), the resolution factor between the peaks due to carbamazepine and carbamazepine impurity A is at least 1.7.

limits

Inject solution (1) and continue the chromatography for 10 times the retention time of carbamazepine, which is about 10 minutes.

In the chromatogram obtained with solution (1):

the area of any secondary peak is not greater than the area of the peak due to carbamazepine in the chromatogram obtained with solution (2) (0.2%);

the sum of the areas of any secondary peaks is not greater than 2.5 times the area of the peak due to carbamazepine in the chromatogram obtained with solution (2) (0.5%).

Disregard any peak with an area less than 0.25 times the area of the peak due to carbamazepine in the chromatogram obtained with solution (2) (0.05%).

Assay

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

(1) Shake a quantity of the powdered tablets containing 0.3 g of Carbamazepine with 100 mL of methanol for 15 minutes. Dilute to 200 mL with water, mix, filter and further dilute 1 volume of the filtrate to 5 volumes with methanol (50%).

(2) 0.03% w/v of carbamazepine BPCRS in methanol (50%).

chromatographic conditions

The chromatographic conditions described under Related substances may be used, with the exception of the run time.