Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ELIDEL vs AZATHIOPRINE SODIUM
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Inhibits T-cell activation by binding to macrophilin-12 (FKBP-12) and inhibiting calcineurin, thereby blocking cytokine transcription.
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.
Atopic dermatitis unresponsive to or intolerant of other topical treatments,Off-label: psoriasis, vitiligo, rosacea, contact dermatitis, lichen sclerosus, cutaneous lupus erythematosus
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
Apply a thin layer of 1% cream to affected areas twice daily.
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.
Terminal elimination half-life: 30–45 hours (mean 35 hours) following topical application; clinically, twice-daily dosing ensures therapeutic concentrations.
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.
Metabolized primarily by CYP3A4; major metabolite O-demethylated pimecrolimus.
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.
Renal (negligible, <1% unchanged) and biliary/fecal (approximately 97% as metabolites); less than 1% of the dose is excreted renally as unchanged drug.
Primarily renal: approximately 50% as unchanged drug and metabolites (6-mercaptopurine, thiouric acid) within 24 hours. Biliary/fecal excretion accounts for minor fraction (<5%).
99% bound to plasma proteins (primarily albumin and alpha-1-acid glycoprotein).
Approximately 30% bound to serum proteins, primarily albumin.
Vd ~ 10 L/kg (extensive tissue distribution); suggests significant extravascular binding and penetration into tissues.
Apparent volume of distribution is 0.6-1.0 L/kg, indicating distribution into total body water and tissues.
Topical: Systemic bioavailability is approximately 4% (range 1–7%) of applied dose; absorption increases with extent of skin lesion and thickness of application.
Oral bioavailability of azathioprine is approximately 60-70% (range 27-82%) due to first-pass metabolism. Intravenous administration yields 100% bioavailability.
No dose adjustment required for any degree of renal impairment.
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.
No formal studies in hepatic impairment; use caution in severe impairment.
Child-Pugh class A: no adjustment. Child-Pugh class B: reduce dose by 50%. Child-Pugh class C: avoid use.
Apply a thin layer of 1% cream twice daily for children aged 2 years and older; not indicated for children under 2 years.
2-5 mg/kg/day IV or oral, divided every 12-24 hours; dose based on body weight (mg/kg).
No specific dose adjustment recommended; apply a thin layer of 1% cream twice daily as for adults.
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.
Long-term safety of topical calcineurin inhibitors has not been established; rare cases of malignancy (e.g., lymphoma, skin cancer) have been reported; use should be limited to short-term and intermittent treatment.
MALIGNANCY: Immunosuppression increases risk of lymphoma and other malignancies, particularly skin cancers. Monitor for neoplasia, especially in renal transplant patients.
Increased risk of infections (e.g., eczema herpeticum, varicella zoster); avoid use on malignant or premalignant skin conditions; lymphadenopathy; photosensitivity; not recommended in patients with Netherton syndrome; potential for systemic immunosuppression; monitor for local irritation.
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.
Hypersensitivity to pimecrolimus or any component of the formulation; history of malignancy; application to areas of active infection; Netherton syndrome; immunocompromised patients.
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).
No known food interactions. Avoid grapefruit juice as it may increase drug levels (CYP3A4 inhibition).
Avoid raw or undercooked meats and fish to reduce infection risk; no specific dietary restrictions; grapefruit juice has no known interaction.
FDA Pregnancy Category C. Systemic exposure is minimal after topical application, but animal studies have shown developmental toxicity. No adequate human studies; risk cannot be excluded. Avoid in pregnancy unless clearly needed.
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.
Not recommended. Pimecrolimus is excreted in milk in animal studies; unknown in humans. M/P ratio not available. Potential for serious adverse reactions in nursing infants.
Contraindicated during breastfeeding due to potential immunosuppression and hematologic toxicity in the nursing infant. M/P ratio: Not established.
No dose adjustment necessary; use minimal amount to control symptoms. Systemic absorption is negligible, so pharmacokinetic changes in pregnancy do not alter dosing.
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.
Topical calcineurin inhibitor for atopic dermatitis, reserved as second-line therapy for mild-to-moderate eczema due to boxed warning for rare malignancy risk. Apply thin layer only; avoid occlusive dressings. Do not use in immunocompromised patients. Intermittent use is recommended; continuous long-term use safety not established.
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.
Apply only to affected skin areas; avoid eyes, mouth, and open wounds.,Use for short durations; do not use continuously for extended periods.,Avoid sun exposure and tanning beds; use sunscreen on treated areas.,Do not cover treated skin with bandages or wraps unless instructed.,Report any signs of infection, skin burning, or new skin growths to your doctor.,This drug is for external use only; wash hands after application unless treating hands.,Do not use if you have a weakened immune system or active skin infection.
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.
No interactions on record
"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."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ELIDEL vs AZATHIOPRINE SODIUM, answered by our medical review team.
ELIDEL is a Topical Calcineurin Inhibitor that works by Inhibits T-cell activation by binding to macrophilin-12 (FKBP-12) and inhibiting calcineurin, thereby blocking cytokine transcription.. 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.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ELIDEL and AZATHIOPRINE SODIUM 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 ELIDEL is: Apply a thin layer of 1% cream to affected areas twice daily.. 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.. 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 ELIDEL and AZATHIOPRINE SODIUM 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. ELIDEL is classified as Category C. FDA Pregnancy Category C. Systemic exposure is minimal after topical application, but animal studies have shown developmental toxicity. No adequate human studies; risk cannot be ex. 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. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.