thanks for writing at healthcaremagic firstly i am really glad that you are concerned about this if i was treating your mom i would have prescribed exactly same medications. lisinoprol is a ACE-inhibitor which is first line drug for high blood pressure whereas metoprolol is b-blocker ,both these medicines are very effective and act by completely different mechanism in controlling blood pressure and usually combination is given for better control of blood pressure in cases where single medicine fails to do so. your mother is having blood pressure in the range which is difficult to control by single medicine that s why a combination is necessary. also regarding side effects ,every drug has its own side effects,however if your mom is having any side effect let doctor know he will replace and will provide an alternate medicine please let me know if this was helpful and feel free to ask for any further quaries