Base-Salt-Ester Weight Conversion Database

There are several factors related to the active pharmaceutical ingredient (API, drug or chemical) to be considered when performing pharmaceutical calculations prior to compounding in the pharmacy. Some factors need to be accounted for and corrected in calculations and some of them do not. If some of these variables are not considered, the final drug concentration in the preparation may be out of the allowable range.

The following discussion presents some summaries on Assay Value and Loss on Drying. Even though these specific topics are not converted in values before compounding, it is important to explain and compare them to the variables that should be converted.

The Assay Values that must be converted are only those that a specific value is provided by the manufacturer of the chemical, such as gentamicin sulfate, etc. where a "potency equivalent" is provided on the label of the manufacturers chemical. Gentamicin has a potency equivalent of not less than 590 µg of gentamicin per mg, calculated on the dried basis. The actual value will be on the label and is to be used in the calculations of the quantity to be used in the prescription.

Following this, there are summaries on Water of Hydration and Base and Salt or Ester conversions.