It must not be used in patients who have severe problems with their liver or who are taking any of the following medicines: • terfenadine, astemizole (commonly used to treat allergy symptoms - these medicines may be available without prescription); • pimozide (used to treat mental illness); • cisapride (used to relieve certain stomach problems); • amiodarone, propafenone, flecainide (used to correct irregular heartbeat); • triazolam, oral (taken by mouth) midazolam (used to relieve anxiety or difficulty sleeping); • simvastatin, lovastatin (used to lower cholesterol); • ergot alkaloids, such as ergotamine, dihydroergotamine, ergonovine and methylergonovine (used to treat migraine headache); • rifampicin (used to treat tuberculosis); • medicines that may interact with Invirase and cause harmful side effects.