Reversible arrhythmias observed in patients treated with recombinant alpha 2 interferon

We have treated 25 patients, 7 with breast cancer and 18 with non-Hodgkin's lymphoma, with recombinant alpha 2 interferon. In 5 patients we observed cardiac arrhythmias that were unexpected and required treatment. No deaths have occurred that we can attribute to interferon, though 1 patient had to be resuscitated. Age, prior cardiac disease, prior treatment with doxorubicin, and interferon dose appear to be predisposing factors for this toxicity.