KEGG DRUG is a comprehensive drug information resource for approved drugs in Japan, USA and Europe, unified based on the chemical structure and/or the chemical component of active ingredients. Each KEGG DRUG entry is identified by the D number and associated with KEGG original annotations including therapeutic targets, drug metabolism, and other molecular interaction network information.

KEGG DGROUP contains structurally and functionally related groups of D number entries in KEGG DRUG. There are five types of drug groups, each identified by the DG number.

• Chemical - grouped as identical chemical structures with minor variations of salts, hydration states, etc.
• Structure - grouped as similar chemical structures having the same skeleton, etc.
• Target - grouped by drug targets
• Class - drug classes often representing similar mechanisms of action
• Metabolism - grouped by substrates, inhibitors and inducers of drug metabolizing enzymes and transporters

Chemical groups are often used for identifying essentially the same active ingredients of drugs in different countries.

KEGG DRUG entries are systematically organized in various ways, utilizing both established and KEGG-original classification systems and focusing on specific features such as drug targets and gene variants.

The generic names of drugs can be different in different countries or organizations. The same structure may be called differently and the same name may mean different structures. To accommodate such differences the generic names are associated with the following codes in parentheses.

• JAN - Japanese Approved Name
• USAN - United States Adopted Name
• NF - National Formulary drug name
• INN - International Nonproprietary Name
• BAN - British Approved Name
• DCF - Dénomination commune française

Specifically, for the drugs in Japan and USA whether they are listed in the pharmacopoeia is denoted by:

• JP18 - Japanese Pharmacopoeia, 18th edition
• USP - United States Pharmacopeia

which also imply the JAN and USAN names, respectively. Furthermore, the drugs in Japan include:

• Non-JPS - Japanese standards for non-Pharmacopoeial crude drugs

for additional crude drugs.

When drug products are available in Japan and/or USA, the following notations are often utilized:

Drug products in Japan and the USA are given D number links for integration in the KEGG MEDICUS resource.

The YJ code is the most widely used drug product code in Japan. It is an extension of the 12-character code used in the drug pricing system of the Japanese Ministry of Health, Labour and Welfare (Korosho). The Korosho code consists of: Drug price standards are determined either by brand name pricing or generic name pricing, and for the latter 01 is given to the brand name digits in the Korosho code. In contrast, YJ codes are assigned with different digits for different products under the same generic name pricing. In KEGG the first nine characters of Korosho codes are named YK codes, which are used to assign D numbers to Japanese drug products.

FDA's National Drug Code (NDC) is used to identify drug products in the USA. Currently, the NDC is a 10-digit code consisting of three segments representing: The first two segments are used to link to/from KEGG D numbers.

There are two additional databases associated with KEGG DRUG/DGROUP.

Drug Interaction Database contains known adverse drug-drug interactions associated with contraindications (CI) and precautions (P) extracted from all the drug labels of Japanese prescription drugs.

• KEGG MEDICUS Drug Interaction Checker

KEGG Drug Structure Maps are part of the KEGG PATHWAY database, graphically illustrating our knowledge of drug development, as many marketed drugs have been developed from lead compounds or existing drugs by introducing chemical structure transformations retaining the core chemical structures.

• KEGG Pathway Maps: Drug Development