Azathioprine Initiation Protocol for Behçet's Disease

Dosing Protocol

The European League Against Rheumatism recommends starting azathioprine at 2.5 mg/kg/day, which is the evidence-based dose shown to decrease hypopyon uveitis attacks and stabilize visual acuity in Behçet's disease 1
Consider a gradual dose escalation approach to minimize gastrointestinal side effects, beginning with 50-100 mg daily and increasing to target dose over 2-4 weeks, and administer with food to reduce nausea 3
Combine azathioprine with systemic corticosteroids, especially during acute inflammatory attacks, as corticosteroids rapidly suppress inflammation while waiting for azathioprine's therapeutic effect 2, 4

Check thiopurine methyltransferase (TPMT) activity prior to initiating therapy, and proceed with standard dosing (2.5 mg/kg/day) for normal TPMT activity, reduce dose (1-1.5 mg/kg/day) for intermediate (heterozygous) TPMT activity, and avoid azathioprine for absent TPMT activity due to high risk of severe myelosuppression 5
Obtain baseline laboratory tests, including liver function tests and renal function tests, before initiating azathioprine therapy 3, 4, 5

Monitor liver function tests monthly for the first 3 months, then every 3 months 6
Monitor for clinical efficacy, including improvement in ocular inflammation (decreased hypopyon uveitis attacks) and stabilization of visual acuity 1, 2

For mild cytopenia, reduce azathioprine dose, and for severe cytopenia, discontinue medication and consult hematology 3, 7
If cytopenia doesn't recover within 1-2 weeks after discontinuation, seek hematology consultation 7

Hematologic toxicity, including leukopenia and thrombocytopenia, can occur with azathioprine therapy, and regular monitoring of complete blood counts is necessary 3, 7
Gastrointestinal symptoms, such as nausea and vomiting, can be managed by taking medication with food, splitting the daily dose, or temporarily reducing the dose 3, 7

Continue azathioprine treatment for at least 2 years for ocular Behçet's disease, and consider indefinite maintenance therapy for severe disease, particularly with ocular involvement 1, 2, 4

Azathioprine is a relative contraindication in pregnancy, and its use should be carefully considered, weighing the benefits and risks 5
Avoid live vaccines during azathioprine treatment, and consider adding cyclosporine A or infliximab to the azathioprine and corticosteroid regimen for refractory eye disease 2, 3, 4, 5