Can different medications effect the pacemaker?

My grandfather is on quite a few different medications, Coumadine, Cozaar, and Bumex (for short) to name a few.  He recently had a pacemaker implanted in him.  Some of the medications are to speed up the heart and some are too slow it down.  He has an irregular heartbeat.  I am wondering why he is on these medications that effect the heart rate even though he has a pacemaker. Isn't that what the pacemaker is for. I would appreciate any advice and answers.  Thank You.

[CCF CARDIO MD JMF]

Dear Tanya,

As is the case with your grandfather, many elderly people have what is called sick sinus syndrome.  Thisis a case where the heart may go excessively fast, but may also go very slow.  the pacemaker is there as a backup if the heart should go slow.  The medications are to keep the heart from going Fast.