Modern ergotism.

A patient taking excessive amounts of an ergot alkaloid for the treatment of migraine headaches developed cool, painful, swollen lower extremities with intermittent claudication and sensory changes. Symptoms subsided and pulses returned within a day of cessation of therapy. "St. Anthony's fire" may be due to stimulation of alpha-adrenergic receptors in the peripheral vasculature. Rebound headache after withdrawal of ergot alkaloids may lead to self-medication and overdosage, with subsequent risk of ergotism.