Brief Answer:
As detailed, also explained in detail about the questions you asked for.

Detailed Answer:
Hi.
Thanks for your query.
Read and understood the history about your Mother, Surgeries, medications and the present problems.

My thoughts:
The problem of the diarrhea has to be well investigated as Immodium although has the property to stop diarrhea it changes the bowel habits, the bacterial flora and such things related to the intestines.
In addition the Nexium and Pepcid have also the effects of either causing diarrhea or constipation.

Nexium and/or Pepcid are known to have drug interactions with many and many medicines including the blood pressure medicines. Hence they are taken differently and only if necessary.

Out of all the medicines she is taking for hypertension, metoprolol and nifedipine in particular do cause effects like loose motions.

All these effects, side effects and untoward effects of medicines on the body can be studied only by stopping one medicine by another, see the improvements if any or changes.
Most of the medicines, particularly the antihypertensive ones can not be altered unless under direct observation of the Physician as they are very important medicines. You will need a Doctor to monitor the blood pressure, the cardiac stability and then alone can have a chance to alter and see the effectiveness.

Nexium and Pepcid can be stopped and see the effects on the body, intestines and blood pressure. These are the ones to control the acid production in the stomach. And in fact should be given only if there is acidity or evidence of inflammation, ulceration of the stomach and duodenum and esophagus.
You may stop these under the guidance of a treating Doctor and have the keen observation as to the changes on the intestinal habits and have regular Blood pressure charting at home by a calibrated blood pressure apparatus. Show it to the Doctor and see the outcome.

Considering the age of your Mother of 91, she should be kept on most minimum possible medicines.

I would advise the following in such a case:
Get the investigations:
- Of Blood - routine, sugar, functions of kidney, liver, thyroid
- Of stool on three different days: this is very important to get a proper diagnosis and possibility of infection can be found out.
- Ultrasonography of the abdomen.
- Considering the age of the patients CT scan be done if urea and creatinine are normal to get better idea about the intestinal problems.
Colonoscopy can rule out any large bowel problems and be done if your Gastroenterologist is ready (considering the age of the patient) and Upper GI is best avoided unless a must.

A proper 5 day trial of an antibiotic, metronidazole may help. (if there is evidence of infection on clinical grounds or if found on investigations.
To give a pre and probiotic and multivitamins for a long time say one to three months. This may help to restore the intestinal bacterial flora and correct the many deficiencies which may not be possible to detect by many tests but are very important for maintaining the normalcy of the body and intestines in particular.
I have a feeling that Immodium has caused most of the problems as the patient enters into the vicious cycle of lose motions alternating with normal/hard stools.

I hope this answer helps you to get a proper diagnosis, and get a proper further treatment. Please feel free to ask for more or if you need further clarifications or if you feel there is a gap of communication.

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