 [ Symptoms ] i have osteopenia i take prevacid and my doctor recommended 1500 mg of calcium daily should i take them together [ Disease ] hi so do we take it she was on top if so then i do not think you have a problem but some high strength antibiotics do reduce the effectiveness of bc pills but please to stop your worries do use plan b if this was within the last 72 hours its called piece of mind do hope this helps you good luck