mercaptopurine (Rx)

Brand and Other Names:Purinethol, Purixan, more...6Mercaptopurine, 6MP
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Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

tablet

  • 50mg

oral suspension

  • 20mg/mL
more...

Acute Lymphatic Leukemia

Induction: 2.5 mg/kg PO qDay; usually 100-200 mg PO qDay in average adult (other agents preferred) 

May increase by 5 mg/kg/day after 4 weeks

Maintenance: 1.5-2.5 mg/kg PO qDay

Reduce dose by 75% if concomitant allopurinol administration

Reduce dose in renal impairment

Crohn Disease (Off-label)

1-1.5 mg/kg PO qHS

Administration

Take on empty stomach to reduce risk of N/V

Other Information

Monitor: CBC, LFTs

Other Indications & Uses

AML

(Off-label): CML, Crohn's disease, ulcerative colitis, histiocytosis X

Dosage Forms & Strengths

tablet

  • 50mg

oral suspension (Purixan)

  • 20mg/mL
more...

Acute Lymphatic Leukemia

Starting dose: 1.25-2.5 mg/kg (50-75 mg/m²) PO qDay 

Maintenance: 1.5-2.5 mg/kg PO qDay in combination with methotrexate

Reduce dose by 75% if concomitant allopurinol administration

Reduce dose in renal impairment

Administration

Take on empty stomach to reduce risk of N/V

Other Information

Monitor: CBC, LFTs

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Interactions

Interaction Checker

and mercaptopurine

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    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

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            Adverse Effects

            >10%

            Elevated LFT's (15%)

            1-10%

            Nausea (10%)

            Vomiting (10%)

            Stomatitis (3-10%)

            Thrombocytopenia (3-10%)

            Rash (1-3%)

            Diarrhea (1-3%)

            Dizziness (1-3%)

            Alopecia (1-3%)

            Leukopenia (1-3%)

            Frequency Not Defined

            Fatigue

            Anorexia

            Headache

            Chills and fever

            Chest pain

            Mucositis

            Upper respiratory infection

            Cough

            Ulceration of intestine

            Ulcerative stomatitis

            Myelosuppression

            Decreased hematocrit

            Hepatotoxicity

            Decreased resistance to infections

            Hyperuricemia

            Nephrotoxicity

            Increased risk of pancreatitis in pts with IBD

            Hyperpigmentation of skin

            Arthralgias

            Eye discomfort

            Tinnitus

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            Warnings

            Black Box Warnings

            The drug should not be used unless a diagnosis of acute lymphatic leukemia has been adequately established, and the patient’s physician is knowledgeable in assessing response to chemotherapy

            Contraindications

            Hypersensitivity; prior resistance to 6-MP or thioguanine

            Not effective for CLL, lymphomas, CNS leukemia

            Cautions

            Renal impairment

            Reduce dose by 75% (ie, give quarter dose) when used concurrently with allopurinol

            Increased risk of bone marrow toxicity

            Avoid pregnancy

            Hepatosplenic T-cell lymphomas

            • Rare postmarketing cases reported primarily in adolescent and young adult patients with Crohn disease and ulcerative colitis treated with TNF blockers
            • Reports have also included a patient being treated for psoriasis and 2 patients being treated for rheumatoid arthritis
            • HSTCL is an aggressive, rare type of T-cell lymphoma (usually fatal)
            • Most reported cases with TNF blockers have occurred with concomitant treatment with azathioprine or 6-mercaptopurine, although there have been cases reported receiving azathioprine or mercaptopurine alone
            • The following HSTCL cases have been identified in the FDA Adverse Event Reporting System (AERS) database, the literature, and the HSTCL Cancer Survivors' Network: infliximab (20), etanercept (1), adalimumab (2), infliximab/adalimumab (5), certolizumab (0), golimumab (0), azathioprine (12), and mercaptopurine (3)
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            Pregnancy & Lactation

            Pregnancy Category: D

            Lactation: not known if excreted in breast milk, do not nurse

            Pregnancy Categories

            A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA:Information not available.

            more...
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            Pharmacology

            Mechanism of Action

            Analog of naturally occurring purines hypoxanthine and guanine

            Purine antagonist, antineoplastic

            Absorption

            Bioavailability: 5-37%

            Peak Plasma Time: 2 hr

            Onset: 2 hr

            Duration: variable

            Distribution

            Protein Bound: 19%

            Vd: 0.56-0.9 L/kg

            Metabolism

            GI mucosa, liver

            Metabolites: 6-thiouric acid

            Elimination

            Half-Life: 21 minutes (children), 47 min (adult)

            Clearance: 11 mL/min/kg

            Excretion: urine

            Dialyzable: no

            Pharmacogenomics

            6-mercaptopurine is activated by guanine phosphoribosyltransferase (HGPRT) to form thioinosine monophosphate (TIMP) and by kinase enzymatic pathways to form active 6-thioguanine nucleotides

            Thiopurine S-methyltransferase (TPMT) inactivates 6-mercaptopurine

            Although complete TPMT deficiency is rare in the general population (0.3%), TPMT screening should be performed prior to administration in all patients prescribed azathioprine or 6-mercaptopurine

            With TPMT deficiency, a larger proportion of 6-mercaptopurine is converted to the cytotoxic 6-thioguanine nucleotide analogues, which can lead to bone marrow toxicity and myelosuppression

            Alleles associated with decreased TPMT enzymatic activity are TPMT*2, TPMT*3A, and TPMT*3C

            Genetic testing laboratories

            • The following companies currently offer testing for TPMT variants
            • Prometheus Labs (http://www.prometheuslabs.com/)
            • Arup Laboratories (http://www.aruplab.com/)
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            Images

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            Formulary

            FormularyPatient Discounts

            Adding plans allows you to compare formulary status to other drugs in the same class.

            To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

            Adding plans allows you to:

            • View the formulary and any restrictions for each plan.
            • Manage and view all your plans together – even plans in different states.
            • Compare formulary status to other drugs in the same class.
            • Access your plan list on any device – mobile or desktop.

            The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
            PA Prior Authorization
            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
            QL Quantity Limits
            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
            ST Step Therapy
            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
            OR Other Restrictions
            Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
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