Mercaptopurine (Purethinol)

Risk
Moderate
Classification Antimetabolite
Cytotoxic, carcinogenic, mutagenic, teratogenic, embryo-lethal
Oncology uses
(*approved by Health Canada)
*ALL
*AML
*CML (palliative)
Contraindications Hypersensitivity
Disease which is resistant to mercaptopurine or thioguanine
Hepatotoxicity (discontinue immediately)
Precautions
(special populations)
Pediatrics: has pediatric indications
Elderly: Use with caution.  Dose reduce in renal or hepatic dysfunction
Pregnancy Category: D
Breastfeeding
Contraindicated (excreted in human breast milk)
Fertility Not known
Side Effects
(clinically significant & frequent > 10%)
Myelosuppression, stomatitis
Hepatotoxicity, LFTs
Hyperuricemia
Drug Interactions Metabolism: hepatic  Avoid: febuxostat, live vaccines, natalizumab, pimecrolimus,  tacrolimus (top)
effect of mercaptopurine: Echinacea
effect of mercaptopurine: 5-ASA, allopurinol, azathioprine, denosumab
effect of: leflunomide
effect of: warfarin (monitor INR)
Caution with other anti-neoplastic agents (unless per protocol)
Usual Oral Dose(s) Protocol & phase dependent
Adult: induction: 2.5 – 5 mg/kg once daily
Maintenance: 1.5 – 2.5 mg/kg once daily
Round to nearest 25mg
Pediatrics: 75 – 100mg/m2 daily at bedtime
Infants < 3 months: dose decrease 50%
Dose Adjustments Excretion: renal Renal: Clcr 50-80 mL/h: q 24-36h dosing interval
10-50 mL/h: q48h
Dialysis: Not dialyzable.
HD, CAPD, CRRT: Administer q48h
Hepatic: Dose adjustment required (no specific guidelines available)
Myelosuppression: modify per protocol or consider dose adjustment in myelosuppression
Available Tablets:  50 mg (scored) – Store at room temp.
Suspension: compounded by pharmacy (refrigerate)
Administration Oral: on an empty stomach
Monitoring Disease progression & toxicities (NCI Common Toxicity Criteria)
Baseline & regular LFTs, CBC
Baseline renal function
Further Information Click here
Last Revision May 2012
Avoid: febuxostat, live vaccines, natalizumab, pimecrolimus,  tacrolimus (top)
 effect of mercaptopurine: Echinacea
 effect of mercaptopurine: 5-ASA, allopurinol, azathioprine, denosumab,
 effect of: leflunomide
 effect of: warfarin (monitor INR)
Caution with other anti-neoplastic agents (unless per protocol)

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