azathioprine (Rx)

Brand and Other Names:Azasan, Imuran
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Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

tablet

  • 50mg
  • 75mg
  • 100mg

powder for injection

  • 100mg/vial
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Kidney Transplantation

Prevention of transplant rejection

3-5 mg/kg/day IV/PO initially on day of transplant or 3 days before transplant (rare) 

Maintenance: 1-3 mg/kg/day IV/PO 

Rheumatoid Arthritis

1 mg/kg/day IV/PO initially in single daily dose or divided q12hr; may be increased by 0.5 mg/kg/day after 6-8 weeks, then by 0.5 mg/kg/day every 4 weeks; not to exceed 2.5 mg/kg/day  

Maintenance: Reduce daily dose by 0.5 mg/kg every 4 weeks until lowest effective dosage is reached

Lupus Nephritis (Off-label)

Induction and maintenance therapy for lupus nephritis (2012 American College of Rheumatology guidelines)

2 mg/kg/day PO with or without low-dose corticosteroids  

Crohn Disease (Off-label)

Maintenance, remission, or reduction of steroid

2-3 mg/kg PO once daily  

Ulcerative Colitis (Off-label)

Maintenance, remission, or reduction of steroid

1.5-2.5 mg/kg PO once daily  

Chronic Refractory Thrombocytopenic Purpura (Off-label)

1-2 mg/kg PO once daily to maximum daily dose of 150 mg for at least 3-6 months before typical response is observed

Dosing considerations

  • Lower dosage (100 mg/day) is reported effective in some patients
  • Longer treatment duration (up to 84 months) is reported in some patients

Dosage Forms & Strengths

tablet

  • 50mg
  • 75mg
  • 100mg

powder for injection

  • 100mg/vial
more...

Juvenile Idiopathic Arthritis

1 mg/kg/day IV/PO initially in single daily dose or divided q12hr; may be increased by 0.5 mg/kg/day after 6-8 weeks, then by 0.5 mg/kg/day every 4 weeks; not to exceed 2.5 mg/kg/day  

Maintenance: Reduce daily dose by 0.5 mg/kg every 4 weeks until lowest effective dosage is reached

Transplantation (Off-label)

Prevention of transplant rejection

3-5 mg/kg/day IV/PO initially on day of transplant or 3 days before transplant (rare)  

Maintenance: 1-3 mg/kg/day IV/PO

Lupus Nephritis (Off-label)

Induction and maintenance therapy for lupus nephritis (2012 American College of Rheumatology guidelines)

<12 years: Safety and efficacy not established

>12 years: 2 mg/kg/day PO with or without low-dose corticosteroids

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Interactions

Interaction Checker

and azathioprine

No Results

     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

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            Adverse Effects

            >10%

            Leukopenia (28-50%)

            Infection (20%)

            <1%

            Lymphoma

            Frequency Not Defined

            Abdominal pain

            Alopecia

            Arthralgia

            Bacterial, fungal, protozoal, viral infections

            Bone marrow suppression

            Diarrhea

            Fever

            Hepatotoxicity

            Macrocytic anemia

            Myalgia

            Nausea or vomiting

            Rash

            Skin cancer

            Steatorrhea

            Sweet syndrome (acute febrile neutrophilic dermatosis)

            Thrombocytopenia

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            Warnings

            Black Box Warnings

            Chronic immunosuppression with this purine antimetabolite increases neoplasia risk, mutagenic risk, and hematologic toxicities

            Reported malignancies include posttransplant lymphoma and hepatosplenic T-cell lymphoma (HSTCL) in patients with inflammatory bowel disease

            Prescribing physicians should be familiar with mutagenic potential and with possible hematologic toxicities

            Contraindications

            Documented hypersensitivity

            Pregnancy, lactation

            Rheumatoid arthritis: Patients previously treated with alkylating agents

            Cautions

            Long-term use increases risk of neoplasia

            Increased risk of infection and hepatotoxicity

            Cases of JC virus-associated infection resulting in progressive multifocal leukoencephalopathy (PML), sometimes fatal, reported in patients treated with immunosuppressants, including azathioprine

            Hepatosplenic T-cell lymphoma

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

            Pregnancy category: D

            Lactation: Drug excreted at low levels in breast milk; use not recommended

            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.

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            Pharmacology

            Mechanism of Action

            Purine antimetabolite, converted to 6-MP; may inhibit synthesis of DNA, RNA, and proteins; interferes with cellular metabolism; may inhibit mitosis

            Absorption

            Well absorbed orally

            Duration: Variable (crosses placenta)

            Peak plasma time: PO, 1-2 hr

            Peak plasma concentration: <1 mcg/mL

            Distribution

            Protein bound: 30%

            Metabolism

            Metabolized in liver

            Metabolites: 6-MP, 6-thiouric acid

            Elimination

            Half-life: Parent drug, 12 min; 6-MP, 0.7-3 hr; slightly prolonged in end-stage renal disease

            Dialyzable: Partially

            Excretion: Urine (primarily as metabolites)

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            Administration

            Oral suspension of 50 mg/mL requires extemporaneous compounding by pharmacist

            IV Incompatibilities

            Stable in neutral or acid solutions; in alkaline solutions, hydrolyzed to 6-MP

            IV Administration

            Can be administered by IV push over 5 minutes at concentration not exceeding 10 mg/mL

            Can be further diluted with NS or D5W and administered by intermittent infusion over 30-60 minutes (usual approach); however, infusions over periods ranging from 5 minutes to 8 hours have been done

            Storage

            Store powder at room temperature (25°C); reconstituted solution is stable for 2 weeks at room temperature but may be less stable under refrigeration

            Protect from light

            Because there are no preservatives, drug must be used within 24 hours

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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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