Rare side effect of proton pump inhibitors?

I am a 35 year old female in good health.  Almost a year ago, I was diagnosed with GERD, probably related to stress.  I started taking Aciphex but within 2-3 months, I became constipated.  I reported this to my doctor, who told me that diarrhea, not constipation was a side effect of proton pump inhibitors.  As I always have problems with constipation and have to watch  my diet/fiber intake, etc, I insisted on switching my medication.  He allowed me to try pantoprazole.  The constipation resolved, but after 2-3 months on pantoprazole, has returned.  Again, he tells me that it is not a side effect of the proton pump inhibitors.  I do not know what to do.  Is this a rare side effect of these medications?  I am miserable with the GERD but almost more miserable with the constipation that seems to accompany these medications for me.  

I also take topirimate 50 mg for migraine but have been taking this for years with no problems.  I did recently switch to the generic from Topamax but my neurologist assures me that this should not affect bowel movements since I tolerated the brand for so long.  Please help.

[Ratnakar Kini, MD]

Hi,
Though diarrhea is more common a side effect of PPI, there are reports that it can cause constipation too. But it is less common.