Phenytoin Capsules
Phenytoin Capsules from different manufacturers, whilst complying with the requirements of the monograph, are not interchangeable.
Action and use
Antiepileptic.
Definition
Phenytoin Capsules contain Phenytoin Sodium.
Content of phenytoin sodium, C15H11N2NaO2
92.5 to 107.5% of the stated amount.
Identification
Related substances
Carry out the method for thin-layer chromatography, Appendix III A, using the following solutions.
10 volumes of 13.5m ammonia, 45 volumes of chloroform and 45 volumes of propan-2-ol.
In the chromatogram obtained with solution (1):
any spot corresponding to benzophenone is not more intense than the spot in the chromatogram obtained with solution (3) (0.5%);
any other secondary spot is not more intense than the spot in the chromatogram obtained with solution (2) (0.5%).
Assay
Shake a quantity of the mixed contents of 20 capsules containing 0.25 g of Phenytoin Sodium with 40 mL of 0.01m sodium hydroxide for 5 minutes and dilute to 50 mL with 0.01m sodium hydroxide. Centrifuge, acidify 25 mL of the clear liquid with 10 mL of 0.1m hydrochloric acid and extract with successive quantities of 50, 40 and 25 mL of ether. Wash the combined extracts with 10 mL of water, evaporate to dryness and dry the residue at 105°. Dissolve in 50 mL of anhydrous pyridine and carry out Method II for non-aqueous titration, Appendix VIII A, using 0.1m tetrabutylammonium hydroxide VS as titrant and a 0.3% w/v solution of thymol blue in anhydrous pyridine as indicator. Each mL of 0.1m tetrabutylammonium hydroxide VS is equivalent to 27.43 mg of C15H11N2NaO2.