mercaptopurine monohydrate: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
mercaptopurine monohydrate: clinical details
Prescribing considerations
- Treatment should be supervised by professionals experienced in managing ALL.
- Assess TPMT status and consider NUDT15 testing; genetic or enzyme testing does not replace blood-count monitoring.
- Review liver and kidney function, infection history, vaccination status, and concomitant myelosuppressive or hepatotoxic treatments.
- Counsel on infection, bleeding, jaundice, sun protection and safe handling of this cytotoxic suspension.
Contraindications and cautions
- Hypersensitivity to mercaptopurine or a formulation excipient.
- Concurrent yellow-fever vaccination.
- The suspension is unsuitable for certain hereditary disorders of sugar metabolism and requires consideration in phenylketonuria because it contains sucrose and aspartame.
Monitoring
- Full blood count, with close attention to falling leucocytes and platelets.
- Liver function, with increased vigilance in pre-existing liver disease or with other hepatotoxic treatment.
- Uric acid during rapid tumour-cell breakdown and renal function where clinically indicated.
- Clinical evidence of infection, pancreatitis, mucosal or skin reactions and secondary malignancy.
Clinical pharmacology
An inactive prodrug converted intracellularly into thioguanine nucleotides. Active metabolites inhibit de novo purine synthesis and nucleotide interconversion and are incorporated into nucleic acids. Metabolism varies with TPMT and NUDT15 activity and includes inactivation through xanthine oxidase.
Formulation and product differences
- The oral suspension must be vigorously redispersed and measured with the supplied oral syringe.
- The oral suspension and tablets are not bioequivalent for peak concentration; intensified haematological monitoring is advised when switching.
- The suspension contains aspartame, parabens and trace sucrose.
- After opening, unused suspension should be discarded after 56 days; store below 25°C with the bottle tightly closed.
mercaptopurine monohydrate preparations and strengths
Oral suspension
Route: Oral
Strengths: 20 mg/mL
mercaptopurine monohydrate interactions
Check all prescribed, non-prescribed and complementary products with the specialist team. Important interactions include:
Allopurinol and other xanthine oxidase inhibitors
They reduce mercaptopurine breakdown and can markedly increase toxicity; specialist adjustment or avoidance is required.
Mesalazine, olsalazine and sulfasalazine
These may inhibit TPMT and increase the risk of bone-marrow toxicity.
Ribavirin
Concurrent use is not advised because severe bone-marrow suppression has been reported.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.