A survey of top 200 drugs--inconsistent practice of drug strength expression for drugs containing salt forms.

Many ionizable drugs are developed and marketed as salt forms. However, there are no clear US regulatory guidelines on drug strength labeling for salts. The strengths of some drugs are expressed as salts and some as free acids/bases. This study surveyed the top 200 US drugs to assess the common practice in industry. The top 200 drugs prescribed in the United States were included in this survey. The drugs containing active pharmaceutical ingredient (API) salts were selected for analysis. Generic or combination products with redundant API salts were excluded. The package insert of each selected drug was reviewed, and the information on drug strength expression was extracted and categorized. Out of the top 200 drugs, 59 unique API salts were identified. The drug strengths were expressed as salts for 32 drugs (54%) and as free acids/bases for 27 drugs (46%). The survey results revealed the inconsistent practice among the industries regarding the drug strength expression for salts. Non-harmonized labeling practice can lead to confusions, potential calculation/dosing errors, and complications in labeling new products. The authors recommend the US Food and Drug Administration to standardize the labeling format for salts and preferably express the drug strengths based on the free acid/base forms.