Concomitant use of Hofergot with cytochrome P450 inhibitors such as macrolide antibiotics (e.g. erythromycin, clarithromycin, troleandomycin, spiramycin, josamycin), azole antimycotics (e.g. ketoconazole, itraconazole), protease inhibitors (e.g. ritonavir, indinavir) or cimetidine must be avoided, as these increase plasma ergotamine levels, possible resulting in peripheral vasoconstriction. Concomitant use of vasoconstrictor agents such as ergotamine, selective vascular 5HT1 receptor agonists or nicotine (e.g. smoking) may increase the risk of vasoconstriction. Although the combination of beta blockers and Hofergot is generally well tolerated, caution is required in susceptible patients.