Propoxyphene and acetaminophen mixture (Darvocet)--related radiation-induced pneumonitis

In a patient undergoing radiation therapy for recurrent, metastatic breast cancer, a mixture of propoxyphene and acetaminophen (Darvocet) was given for intercurrent viral infection. Discontinuation of therapy with this medication coincided with appearance of pneumonitis, reminiscent of the steroid withdrawal--related radiation pneumonitis.