Mercaptopurine (Purinethol)

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General information

Class/mechanism: Purine analog of adenine and hypoxanthine, antimetabolite that interferes with DNA synthesis. Mercaptopurine competes with hypoxanthine and guanine for the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) and is converted to thioinosinic acid (TIMP). TIMP inhibits reactions that typically involve inosinic acid (IMP), such as its conversion to xanthylic acid (XMP) and adenylic acid (AMP) via adenylosuccinate (SAMP). TIMP is also converted to 6-methylthioinosinate (MTIMP); TIMP and MTIMP have been observed to inhibit glutamine-5-phosphoribosylpyrophosphate amidotransferase, which is an early enzyme in the de novo pathway of purine ribonucleotide synthesis. Mercaptopurine is structurally and functionally similar to Thioguanine (Tabloid).[1][2][3][4]
Route: PO
Extravasation: n/a

For conciseness and simplicity, currently will focus on treatment regimens and not list information such as: renal/hepatic dose adjustments, metabolism (including CYP450), excretion, monitoring parameters (although this will be considered for checklists), or manufacturer. Instead, for the most current information, please refer to your preferred pharmacopeias such as Micromedex, Lexicomp, UpToDate (courtesy of Lexicomp), or the prescribing information.[1]

Diseases for which it is used

Patient drug information

History of changes in FDA indication

Also known as

  • Generic names: 6-MP, 6-Mercaptopurine
  • Brand names: Purinethol, Purixan (oral suspension formulation)


  1. 1.0 1.1 Mercaptopurine (Purinethol) package insert
  2. Mercaptopurine (Purinethol) package insert (locally hosted backup)
  3. Mercaptopurine (Purixan) package insert
  4. Mercaptopurine (Purixan) package insert (locally hosted backup)
  5. Mercaptopurine (Purinethol) patient drug information (Chemocare)
  6. Mercaptopurine (Purinethol) patient drug information (UpToDate)