Sulfadimidine or sulfamethazine, is a sulfonamide

Sulfonamide (medicine)

Sulfonamide or sulphonamide is the basis of several groups of drugs. The original antibacterial sulfonamides are synthetic antimicrobial agents that contain the sulfonamide group. Some sulfonamides are also devoid of antibacterial activity, e.g., the anticonvulsant sultiame...

 antibacterial.

There are non-standardized abbreviations for it as "sulfadimidine" (abbreviated SDI and more commonly but less reliably SDD) and as "sulfamethazine" (abbreviated SMT and more commonly but less reliably SMZ). Other names include sulfadimerazine, sulfadimezine, and sulphadimethylpyrimidine.

Further reading

• ChemDB. "Sulfamethazine", ChemDB, National Institute of Allergy and Infectious Diseases
  National Institute of Allergy and Infectious Diseases
  The National Institute of Allergy and Infectious Diseases is one of the 27 institutes and centers that make up the National Institutes of Health , an agency of the United States Department of Health and Human Services...
  
   (NIAID), National Institutes of Health
  National Institutes of Health
  The National Institutes of Health are an agency of the United States Department of Health and Human Services and are the primary agency of the United States government responsible for biomedical and health-related research. Its science and engineering counterpart is the National Science Foundation...
  
   (NIH)
• U.S. National Library of Medicine: ChemIDplus - Sulfamethazine
• PubChem. "Sulfamethazine - Substance Summary", PubChem
  PubChem
  PubChem is a database of chemical molecules and their activities against biological assays. The system is maintained by the National Center for Biotechnology Information , a component of the National Library of Medicine, which is part of the United States National Institutes of Health . PubChem can...
  
  , National Center for Biotechnology Information
  National Center for Biotechnology Information
  The National Center for Biotechnology Information is part of the United States National Library of Medicine , a branch of the National Institutes of Health. The NCBI is located in Bethesda, Maryland and was founded in 1988 through legislation sponsored by Senator Claude Pepper...
  
   (NCBI), National Library of Medicine (NLM), National Institutes of Health
  National Institutes of Health
  The National Institutes of Health are an agency of the United States Department of Health and Human Services and are the primary agency of the United States government responsible for biomedical and health-related research. Its science and engineering counterpart is the National Science Foundation...
  
  (NIH)