Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
AZATHIOPRINE SODIUM vs GENGRAF
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Azathioprine is a prodrug of 6-mercaptopurine. It inhibits purine synthesis by interfering with the synthesis of DNA, RNA, and cellular proteins, thereby suppressing immune responses.
Calcineurin inhibitor; binds to cyclophilin, inhibits calcineurin-dependent T-cell activation, preventing nuclear factor of activated T-cells (NF-AT) dephosphorylation and translocation, thereby reducing IL-2 and other cytokine gene transcription.
Renal transplantation (adjunctive immunosuppression),Rheumatoid arthritis (active, severe, not responsive to conventional therapy),Off-label: Inflammatory bowel disease (Crohn's disease, ulcerative colitis), autoimmune hepatitis, systemic lupus erythematosus, vasculitis, myasthenia gravis, pemphigus vulgaris
Prophylaxis of organ rejection in kidney, liver, and heart allogeneic transplants,Treatment of active rheumatoid arthritis (FDA-approved for moderate to severe),Treatment of psoriasis (FDA-approved for severe, recalcitrant cases),Off-label: nephrotic syndrome, aplastic anemia, ulcerative colitis, atopic dermatitis
1-2 mg/kg/day IV or oral, initially; maintenance 0.5-1 mg/kg/day IV or oral. For severe organ rejection: 3-5 mg/kg/day IV.
5-15 mg/kg/day orally in divided doses every 12 hours.
Terminal elimination half-life of azathioprine is approximately 3-5 hours; its active metabolite 6-mercaptopurine has a half-life of 0.5-1.5 hours. However, the pharmacodynamic effect (immunosuppression) persists longer due to intracellular accumulation of thioguanine nucleotides.
Terminal half-life is approximately 8.4 hours (range 5-18 hours) in adult volunteers; prolonged in hepatic impairment.
Primarily metabolized by xanthine oxidase (XO) and thiopurine methyltransferase (TPMT) to active and inactive metabolites. Also metabolized by aldehyde oxidase and glutathione S-transferase. Concomitant use with allopurinol (XO inhibitor) requires dose reduction.
Hepatic metabolism primarily via CYP3A4 enzyme; also substrate for CYP3A5. Metabolized to multiple metabolites with variable activity, including AM1 (hydroxylated), AM9 (N-demethylated), and AM4N (cyclized). Undergoes extensive first-pass metabolism.
Primarily renal: approximately 50% as unchanged drug and metabolites (6-mercaptopurine, thiouric acid) within 24 hours. Biliary/fecal excretion accounts for minor fraction (<5%).
Primarily biliary/fecal (94%); renal excretion accounts for 6% (0.1% unchanged).
Approximately 30% bound to serum proteins, primarily albumin.
90-98% bound to plasma proteins, primarily lipoproteins, albumin, and alpha-1-acid glycoprotein.
Apparent volume of distribution is 0.6-1.0 L/kg, indicating distribution into total body water and tissues.
3.5 L/kg (range 1.2-4.8 L/kg) in renal transplant recipients; distribution is extensive and variable.
Oral bioavailability of azathioprine is approximately 60-70% (range 27-82%) due to first-pass metabolism. Intravenous administration yields 100% bioavailability.
Oral bioavailability is 30% (range 10-60%), variable due to first-pass metabolism and food effects.
GFR 50-80 m L/min: no adjustment. GFR 30-50 m L/min: reduce dose by 25% to 50%. GFR 10-30 m L/min: reduce dose by 50% to 75%. GFR <10 m L/min: avoid or use with extreme caution.
GFR <30 m L/min: reduce dose by 50%.
Child-Pugh class A: no adjustment. Child-Pugh class B: reduce dose by 50%. Child-Pugh class C: avoid use.
Child-Pugh Class A: no adjustment; Class B: reduce dose by 50%; Class C: avoid use.
2-5 mg/kg/day IV or oral, divided every 12-24 hours; dose based on body weight (mg/kg).
4-10 mg/kg/day orally in divided doses every 12 hours; adjusted to target trough levels.
Start at lower end of dosing range; monitor renal function and adjust accordingly. Consider reduced initial dose (e.g., 1 mg/kg/day) due to age-related decreased renal function.
Initiate at lower end of dosing range and titrate based on renal function and drug levels.
MALIGNANCY: Immunosuppression increases risk of lymphoma and other malignancies, particularly skin cancers. Monitor for neoplasia, especially in renal transplant patients.
Increased susceptibility to infection and development of lymphoma and other malignancies, particularly of the skin. Only physicians experienced in immunosuppressive therapy and management of transplant patients should prescribe cyclosporine.
Hematotoxicity (leukopenia, thrombocytopenia, anemia) - monitor CBC. Hepatotoxicity - monitor liver function tests. Increased infection risk. Pancreatitis. Hypersensitivity reactions. Increased risk of malignancy (skin cancer, lymphoma). Use with caution in renal/hepatic impairment. Test for TPMT deficiency before use.
Nephrotoxicity: Monitor renal function regularly; risk increased with high doses, other nephrotoxic drugs, or prolonged use.,Hepatotoxicity: Monitor liver function.,Hypertension: Common; require blood pressure control.,Neurotoxicity: Including tremor, convulsions, headache, and paresthesias.,Hyperkalemia: Monitor serum potassium, especially with potassium-sparing diuretics or ACE inhibitors.,Hypomagnesemia: Supplementation may be required.,Increased risk of infections and lymphoproliferative disorders.,Potential for anaphylactic reactions with IV formulation (due to Cremophor EL).,Carcinogenesis: Especially skin malignancies; minimize UV exposure.
Hypersensitivity to azathioprine or 6-mercaptopurine. Severe active infection. Pregnancy (FDA Category D), especially first trimester. Lactation. Concomitant use with allopurinol (unless dose adjusted). TPMT deficiency (increased risk of severe myelotoxicity).
Hypersensitivity to cyclosporine or any component of the formulation (including Cremophor EL for IV),Uncontrolled hypertension,Malignancy (except non-melanoma skin cancer) in patients with rheumatoid arthritis or psoriasis,Concomitant use with PUVA or UVB therapy, methotrexate, other immunosuppressive agents, or coal tar (for psoriasis patients),Abnormal renal function with uncontrolled hypertension (for psoriasis patients),Pregnancy (category C; additional risk of premature birth and low birth weight)
Avoid raw or undercooked meats and fish to reduce infection risk; no specific dietary restrictions; grapefruit juice has no known interaction.
Grapefruit and grapefruit juice increase cyclosporine levels and must be avoided. High-potassium foods (e.g., bananas, oranges, potatoes) may increase hyperkalemia risk; monitor intake. Avoid St. John's wort as it reduces drug levels.
FDA Category D. Hematologic toxicity and immunosuppression in the neonate. Increased risk of congenital malformations (cleft palate, skeletal anomalies) and fetal growth restriction. First trimester exposure associated with highest risk; second and third trimester risks include intrauterine growth restriction and preterm birth.
First trimester: Cyclosporine crosses the placenta. Limited human data, but no major malformations attributed. Second and third trimesters: Risk of intrauterine growth restriction, prematurity, and low birth weight. Consider risk-benefit; avoid if possible, but may be used if essential.
Contraindicated during breastfeeding due to potential immunosuppression and hematologic toxicity in the nursing infant. M/P ratio: Not established.
Cyclosporine is excreted into breast milk. Milk-to-plasma ratio approximately 0.3-0.6. Potential for infant immunosuppression and growth inhibition. Weigh benefits against risks; monitor infant for adverse effects.
Azathioprine dose may need to be reduced due to increased clearance in pregnancy; monitor 6-thioguanine nucleotide levels. Empiric dose adjustments not standardized; titrate to maintain therapeutic effect while minimizing myelotoxicity.
Pregnancy reduces cyclosporine oral bioavailability and increases clearance; dose may need to be increased by 20-50% to maintain therapeutic trough levels. Frequent level monitoring recommended, especially in third trimester. Postpartum dose reduction likely needed.
Monitor CBC and LFTs weekly for first month, then biweekly for next 2 months, then monthly; dose reduction required with allopurinol coadministration (reduce to 25% of usual dose); screen for TPMT and NUDT15 deficiency before initiating therapy; avoid live vaccines; increased risk of lymphoproliferative disorders; use sun protection due to photosensitivity; pregnancy category D.
Monitor trough levels (target 100-400 ng/m L) and renal function closely. Calcineurin inhibitors cause nephrotoxicity; dose reduction may be necessary. Avoid use with potassium-sparing diuretics or ACE inhibitors due to hyperkalemia risk. Grapefruit increases levels; avoid coadministration. Remember to adjust dose for hepatic impairment.
Take exactly as prescribed, do not stop without consulting your doctor.,Report any signs of infection (fever, sore throat, easy bruising or bleeding) immediately.,Use effective contraception during treatment and for at least 3 months after stopping.,Avoid live vaccines (e.g., MMR, varicella, nasal flu) while on this medication.,Limit sun exposure and use broad-spectrum sunscreen and protective clothing.,Do not take allopurinol without your doctor's knowledge.,Attend all scheduled blood tests to monitor for side effects.,May cause nausea; take with food if upset stomach occurs.
Take with or without food consistently at the same times each day.,Do not consume grapefruit or grapefruit juice while on this medication.,Report signs of infection, tremors, or changes in urine output immediately.,Avoid live vaccinations and limit sun exposure due to increased skin cancer risk.,Do not stop or change dose without consulting your doctor.
"Azathioprine may reduce the therapeutic efficacy and cardiotoxic effects of digitoxin by accelerating its metabolism through induction of cytochrome P450 enzymes, particularly CYP3A4. This interaction can lead to decreased digitoxin serum concentrations, potentially resulting in loss of heart rate control in patients with atrial fibrillation or heart failure. Conversely, the cardiotoxic risk of digitoxin is diminished, but the therapeutic goal may be compromised."
"Azathioprine and fingolimod both suppress lymphocyte function, leading to additive or synergistic immunosuppression. This combination increases the risk of severe infections, including opportunistic infections, due to profound immune system suppression. Clinically, patients may present with prolonged lymphopenia, increased susceptibility to infections, and potential reactivation of latent viruses such as JC virus (causing progressive multifocal leukoencephalopathy) or cytomegalovirus."
"Azathioprine, an immunosuppressant that acts as a prodrug for 6-mercaptopurine, can increase the myelosuppressive effects of benazepril, an ACE inhibitor. This interaction is likely due to additive bone marrow suppression, leading to an elevated risk of leukopenia, anemia, and thrombocytopenia, especially in patients with renal impairment or concomitant use of other myelosuppressive agents."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about AZATHIOPRINE SODIUM vs GENGRAF, answered by our medical review team.
AZATHIOPRINE SODIUM is a Immunosuppressant that works by Azathioprine is a prodrug of 6-mercaptopurine. It inhibits purine synthesis by interfering with the synthesis of DNA, RNA, and cellular proteins, thereby suppressing immune responses.. GENGRAF is a Calcineurin Inhibitor Immunosuppressant that works by Calcineurin inhibitor; binds to cyclophilin, inhibits calcineurin-dependent T-cell activation, preventing nuclear factor of activated T-cells (NF-AT) dephosphorylation and translocation, thereby reducing IL-2 and other cytokine gene transcription.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between AZATHIOPRINE SODIUM and GENGRAF depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of AZATHIOPRINE SODIUM is: 1-2 mg/kg/day IV or oral, initially; maintenance 0.5-1 mg/kg/day IV or oral. For severe organ rejection: 3-5 mg/kg/day IV.. The standard adult dose of GENGRAF is: 5-15 mg/kg/day orally in divided doses every 12 hours.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between AZATHIOPRINE SODIUM and GENGRAF in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. AZATHIOPRINE SODIUM is classified as Category D/X. FDA Category D. Hematologic toxicity and immunosuppression in the neonate. Increased risk of congenital malformations (cleft palate, skeletal anomalies) and fetal growth restrictio. GENGRAF is classified as Category C. First trimester: Cyclosporine crosses the placenta. Limited human data, but no major malformations attributed. Second and third trimesters: Risk of intrauterine growth restriction,. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.