Usage period pharmacy preparations

For pharmacy preparations, usage periods per dosage form are given in Table 22.7. These general suggestions are mostly based on microbiological factors, and sometimes on physical properties. Often they may also be used for licensed medicines. See Sect. 22.7. for details. 

When performing stability studies on medicines to determine shelf-life and usage periods, it is shown that chemical degradation may be fairly predictable but shelf life and usage periods may be influenced by less predictable causes. Changes that can be observed by the patient offer another perspective. The last section of the chapter provides advice on storage conditions, shelf life and usage periods of pharmacy preparations. 

Extemporaneous preparations, with unknown or uncertain chemical or physical stability, carmot be kept on stock in the pharmacy. They have a maximum usage period according to Table 22.15, but this period is not more than 1 month for liquid and semisolid preparations, and not more than 6 months for dry forms. If the formula is similar to a standardised one, the maximum shelf life of that standardised formula can be used. 

Storage instructions that are important for the usage period should be on the label (e.g. Keep refrigerated, or Store at room temperature). Sometimes only the pharmacy stock needs to be kept in the refrigerator, while this is not necessary for the short period the patient uses the medicine. Examples are Acetic acid Ear drops and Atimos or Foradil aerosol. Both ear drops and preparations for inhalation should be at least at room temperature when used, because low temperatures can be unpleasant for the patient. 

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