Will quinupristin-dalfopristin interact with other medicines?

Yes, it is possible. Taking quinupristin-dalfopristin (brand name Synercid) with a group of medicines called calcium channel blockers could cause the amount of calcium channel blocker in your body to go up because Synercid slows the breakdown, or metabolism, of many calcium channel blockers, including amlodipine, nifedipine, diltiazem, verapamil, felodipine, isradipine, nicardipine, nilvadipine, nimodipine, nisoldipine and nitrendipine. The only calcium channel blocker that is not affected by Synercid is clevidipine. Another drug whose breakdown is slowed by Synercid is cyclosporine, a drug used to suppress the immune system in people with transplantated organs. The increased amounts of cyclosporine in your blood may result in dangerous side effects, so your doctor may decide to use a different antibiotic.