6-mercaptopurine (Purinethol, 6-MP, Mecaleukin, Leukerin, Leupurin)
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Introduction
Tradename: Purinethol.
Indications
Dosage
- 70-100 mg/m2/day
- reduce by 75% (20-25 mg/m2/day) if used in combination with allopurinol
- dosage adjustment for renal insufficiency
Tabs: 50 mg.
Pharmacokinetics
- well absorbed orally
- poor systemic circulation availability
- systemic availability increased with allopurinol
- well distributed to tissues
- metabolized by xanthine oxidase to thioinosinic acid
- 50% eliminated in the urine
- 1/2life is 1 hour
elimination via kidney
Adverse effects
- common (> 10%)
- intrahepatic cholestasis & centrolobular necrosis
- increased AST, alkaline phosphatase, bilirubin
- jaundice
- less common (1-10%)
- hyperpigmentation, rash, hyperuricemia, nausea/vomiting, diarrhea, stomatitis, anorexia, stomach pain, mucositis
- renal toxicity, leukopenia, thrombocytopenia, anemia may occur at higher doses
- more GI toxic than 6-thioguanine
- myelosuppression
- moderate (platelets & leukocytes)
- onset: 7-10 days
- nadir: 14 days
- recovery: 21 days
- uncommon (< 1%)
- drug fever, scaling rash, glossitis, tarry stools, eosinophilia
- other[2] headache
Drug interactions
- coadministration of allopurinol
- may potentiate myelosuppression
- increases serum concentrations by 60%
- warfarin
- Bactrim
Test interactions
increases serum K+
Laboratory
- consider baseline thiopurine methyltransferase in erythrocytes to assess likelihood of myelosuppression[5]
Mechanism of action
- purine antagonist, S-phase specific
- inhibits DNA & RNA synthesis
Mechanism of drug resistance:
- diminished activity of hypoxanthine-guanine phosphoribosyl transferase (HGPRT)
More general terms
Additional terms
References
- ↑ Kaiser Permanente Northern California Regional Drug Formulary, 1998
- ↑ 2.0 2.1 Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
- ↑ Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 533
- ↑ Wikipedia: Mercaptopurine http://en.wikipedia.org/wiki/Mercaptopurine
- ↑ 5.0 5.1 Medical Knowledge Self Assessment Program (MKSAP) 17, American College of Physicians, Philadelphia 2015