© 2017 International Medical Press. An HIV-infected patient treated with tenofovir disoproxil fumarate/emtricitabine/elvitegravir/cobicistat developed severe acute ischaemia of both legs during a migraine episode. After being interrogated he admitted taking an ergotamine-containing preparation. Ergotism due to interaction between ergotics and cobicistat was diagnosed. We describe the first reported case of this interaction.