Packaging and storage— Preserve in well-closed containers.

Identification— Transfer the contents of 1Capsule to a beaker,add 10mLof 3Nhydrochloric acid and 5drops of methyl red TS,heat to boiling,add 6Nammonium hydroxide until the color of the solution changes to deep yellow,then continue boiling for 2minutes,and filter:the filtrate so obtained responds to the tests for Magnesium á191ñ.

Dissolution á711ñ—

Uniformity of dosage units á905ñ: meet the requirements.

Acid-neutralizing capacity á301ñ: not less than 5mEq of acid is consumed by the minimum single dose recommended in the labeling,and not less than 85.0%of the expected mEq value calculated from the results of the Assayis obtained.Each mg of MgOhas an expected acid-neutralizing capacity value of 0.0492mEq.

Assay— Weigh accurately the contents of not fewer than 20Capsules,and mix.Transfer an accurately weighed portion of the powder,equivalent to about 500mg of magnesium oxide,to a beaker,add 20mLof water,and slowly add 40mLof 3Nhydrochloric acid,with mixing.Heat the mixture to boiling,cool,and filter into a 200-mLvolumetric flask.Wash the beaker with water,adding the washings to the filter.Add water to volume,and mix.Transfer 20.0mLof this solution to a 400-mLbeaker,add 180mLof water and 20mLof triethanolamine,and stir.Add 10mLof ammonia–ammonium chloride buffer TSand 3drops of an eriochrome black indicator solution prepared by dissolving 200mg of eriochrome black Tin a mixture of 15mLof triethanolamine and 5mLof dehydrated alcohol,and mix.Cool the solution to between 3and 4by immersion of the beaker in an ice bath,then remove,and titrate with 0.05Medetate disodium VSto a blue endpoint.Perform a blank determination,substituting 20mLof water for the assay solution,and make any necessary correction.Each mLof 0.05Medetate disodium consumed is equivalent to 2.015mg of magnesium oxide (MgO).

Expert Committee:(PA4)Pharmaceutical Analysis 4

USP28–NF23Page 1172

Phone Number:1-301-816-8251