Phenobarbital Sodium
C12H11N2NaO3 254.22

2,4,6(1H,3H,5H)-Pyrimidinetrione,5-ethyl-5-phenyl-,monosodium salt.
Sodium 5-ethyl-5-phenylbarbiturate [57-30-7].
»Phenobarbital Sodium contains not less than 98.5percent and not more than 101.0percent of C12H11N2NaO3,calculated on the dried basis.
Packaging and storage— Preserve in tight containers.
Labeling— Where it is intended for use in preparing injectable dosage forms,the label states that it is sterile or must be subjected to further processing during the preparation of injectable dosage forms.
Completeness of solution— Mix 1.0g with 10mLof carbon dioxide-free water:after 1minute,the solution is clear and free from undissolved solid.
Identification—
A: Dissolve about 50mg of Phenobarbital Sodium in 15mLof water in a separator,add 2mLof hydrochloric acid,shake,and extract the liberated phenobarbital with four 25-mLportions of chloroform.Filter the combined extracts through a pledget of cotton or other suitable filter into a beaker,and wash the separator and the filter with several small portions of chloroform.Evaporate a 50-mLportion of the chloroform solution of phenobarbital on a steam bath with the aid of a current of air.Add 10mLof ether,again evaporate,and dry the residue at 105for 2hours:the IRabsorption spectrum of a potassium bromide dispersion of the residue so obtained exhibits maxima only at the same wavelengths as that of a similar preparation of USP Phenobarbital RS.
B: Ignite about 200mg:the residue effervesces with acids,and responds to the tests for Sodium á191ñ.
C: The relative retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.
pHá791ñ: between 9.2and 10.2,in the solution prepared in the test for Completeness of solution.
Loss on drying á731ñ— Dry it at 150for 4hours:it loses not more than 7.0%of its weight.
Heavy metals á231ñ— Dissolve 2.0g in 52mLof water.Add slowly,with vigorous stirring,8mLof 1Nhydrochloric acid,and filter,discarding the first 5mLof the filtrate.Dilute 20mLof the subsequent filtrate with water to 25mL:the limit is 0.003%.
Organic volatile impurities,Method Iá467ñ: meets the requirements.
Other requirements— Where the label states that Phenobarbital Sodium is sterile,it meets the requirements for Sterility Tests á71ñand for Bacterial endotoxinsunder Phenobarbital Sodium for Injection.Where the label states that Phenobarbital Sodium must be subjected to further processing during the preparation of injectable dosage forms,it meets the requirements for Bacterial endotoxinsunder Phenobarbital Sodium for Injection.
Assay—
pH4.5Buffer solution,Mobile phase,Internal standard solution,Standard preparation,and Chromatographic system— Prepare as directed in the Assayunder Phenobarbital.
Assay preparation— Transfer about 22mg of Phenobarbital Sodium,accurately weighed,to a conical flask,add 15.0mLof Internal standard solution,mix,and sonicate for 15minutes.Pass through a membrane filter having a 0.5-µm or finer porosity before use.
Procedure— Proceed as directed for Procedurein the Assayunder Phenobarbital.Calculate the quantity,in mg,of C12H11N2NaO3in the portion of Phenobarbital Sodium taken by the formula:
(254.22/232.24)(W)(RU/RS),
in which 254.22and 232.24are the molecular weights of phenobarbital sodium and phenobarbital,respectively;and the other terms are as defined therein.
Auxiliary Information— Staff Liaison:Ravi Ravichandran,Ph.D.,Senior Scientist
Expert Committee:(PA3)Pharmaceutical Analysis 3
USP28–NF23Page 1531
Phone Number:1-301-816-8330