When scientists develop a new drug, they give it a generic name reflecting its chemical makeup. Once the Food and Drug Administration (FDA) approves the drug, the manufacturer markets it with a brand or trade name, which is usually shorter and easier to remember. A drug company can hold exclusive patent rights to make a drug for 20 years after its discovery. After that, other companies can start making generic versions of the drug.

      Sources:

• Law Notes. FDA Position on Product Selection for "Narrow Therapeutic Index" Drugs, American Journal of Health-System Pharmacy 54 (1997).
  
• Levy G. "What are Narrow Therapeutic Index Drugs?" Clinical Pharmacology & Therapeutics May (1998).
  
• Mayo Clinic Family Health Book. William Morrow & Co., 1996.
  
• Merck Manual of Medical Information: Home Edition. Merck & Co., 1997.
  
• Yorke, J. "FDA Ensures Equivalence of Generic Drugs," FDA Consumer Special Report on New Drug Development in the United States Special Ed. January (1995).