Assay of unit-dose medicines

Unit-dose medicines are preparations that contain doses designed to be taken separately. Examples of this type of preparation include tablets, capsules, suppositories or pessaries. To determine the purity of unit-dose medicines, the calculations outlined above need to be modified, in order to determine how much drug is present in each individual dosage form. The 

An example of this type of calculation is the assay of Lithium Carbonate Tablets BP. Lithium carbonate is used as an antidepressant in 250 mg and 400 mg strengths. The BP assay is to weigh and powder 20 tablets. Add a quantity of the powder containing 1 g of lithium carbonate to 100 mL of water add 50 mL of 1 M hydrochloric acid and boil for 1 minute to remove carbon dioxide. Cool and titrate the excess acid with 1 m sodium hydroxide solution using methyl orange as indicator. The assay is then repeated omitting the sample. 

Therefore, since the relative molecular mass of Li2C03 is 73.9, 

The assay was carried out and the following results were obtained. 

The number of tablets assayed is given by Sample weight 

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