No serious adverse effects were observed with the moderate doses and short durations typical of urticaria applications. Leg swelling was observed in 2 patients and of sufficient severity that one chose to avoid future use despite excellent clinical results. Major adverse effects include headache, alimentary complaints, extremity edema, rash, tremor, arthralgias, fatigue, weight gain, dyslipoproteinaemia (probably to a lesser degree than would be expected with a regimen of cyclosporine), cytopenias, and immune suppression-related neoplasia or infections. Sirolimus is a substrate of cytochrome P450 3A4, which may give rise to important drug interactions. As with other alternative agents,11- 13 urticaria, angioedema, and drug rash have been reported as adverse effects, mainly in renal transplant recipients.14 Laboratory monitoring included baseline blood counts, renal function, and hepatic enzymes and interval blood counts. Weight, fluid status, and evidence of infectious complications were also assessed.