After 50 years, this authoritative index continues to reign as the standard international pharmaceutical reference on medications, proprietary names, synonyms, chemical structures, and therapeutic classes of substances.. This 19^th edition offers improved search functionality and includes 70,000 proprietary names (19,000 more than the previous edition) from more than 12,000 manufacturers representing 171 countries. It also contains an updated and edited collection of active substances and derivatives (4,000 total) with international non-proprietary names (INN) and 12,000 synonyms.