Primidone Tablets

General Notices

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

Action and use

Antiepileptic.

Definition

Primidone Tablets contain Primidone.

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

Content of primidone, C12H14N2O2

95.0 to 105.0% of the stated amount.

Identification

Extract a quantity of the powdered tablets containing 0.5 g of Primidone with 50 mL of hot ethanol (96%), filter and evaporate the filtrate to dryness. The residue complies with the following tests.

A. The infrared absorption spectrum, Appendix II A, is concordant with the reference spectrum of primidone (RS 286).
B. Dissolve 0.1 g in 5 mL of chromotropic acid-sulfuric acid solution and heat in a water bath for 30 minutes. A pinkish blue colour is produced.

2-Ethyl-2-phenylmalondiamide

Dissolve 25 mg of octadecan-1-ol (internal standard) in sufficient pyridine to produce 50 mL (solution A). Carry out the method for gas chromatography, Appendix III B, using the following solutions. For solution (1) add 2 mL of solution A and 1 mL of N,O-bis(trimethylsilyl)acetamide to 2 mL of a 0.050% w/v solution of 2-ethyl-2-phenylmalondiamide in pyridine. For solution (2) mix of a quantity of the powdered tablets containing 0.1 g of Primidone with 2 mL of pyridine, add 2 mL of solution A and 1 mL of N,O-bis-(trimethylsilyl)acetamide, allow to stand at 100° for 5 minutes, cool and dilute to 10 mL with pyridine. Prepare solution (3) in the same manner as solution (2) but use 4 mL of pyridine and omit the addition of solution A.

The chromatographic procedure may be carried out using a glass column (1.5 m × 4 mm) packed with acid-washed, silanised diatomaceous support (100 to 120 mesh) coated with 3% w/w of phenyl methyl silicone fluid (50% phenyl) (OV-17 is suitable) and maintained at 170°.

In the chromatogram obtained with solution (2) the ratio of the area of any peak derived from 2-ethyl-2-phenylmalondiamide to the area of the peak derived from the internal standard is not greater than the corresponding ratio in the chromatogram obtained with solution (1).

Assay

Weigh and powder 20 tablets. Dissolve 0.24 g of N-phenylcarbazole (internal standard) in sufficient methanol to produce 100 mL (solution A). Carry out the method for gas chromatography, Appendix III B, using the following solutions. For solution (1) add 25 mL of solution A to 0.15 g of primidone BPCRS and dilute to 50 mL with methanol, warming to dissolve if necessary. For solution (2) add 100 mL of methanol to a quantity of the powdered tablets containing 0.3 g of Primidone, heat on a water bath for 5 minutes, shaking occasionally, cool, allow any undissolved material to settle and use the clear supernatant liquid. Prepare solution (3) in the same manner as solution (2) but add 50 mL of solution A and 50 mL of methanol in place of 100 mL of methanol.

The chromatographic procedure may be carried out using a glass column (1.5 m × 4 mm) packed with acid-washed, silanised diatomaceous support (100 to 120 mesh) coated with 3% w/w of phenyl methyl silicone fluid (50% phenyl) (OV-17 is suitable) and maintained at 260°.

Calculate the content of C12H14N2O2 using the declared content of C12H14N2O2 in primidone BPCRS.