Interactions may occur when erythromycin or clarithromycin is taken with the following: Warfarin: Further elevation of the prothrombin time / international normalized ratio (PT / INR) Lovastatin and simvastatin: Rhabdomyolysis Midazolam and triazolam: Somnolence Theophylline: Nausea, vomiting, and seizures Tacrolimus, cyclosporine, and ergot alkaloids: Elevated serum levels of these drugs