Drug interactions

My wife, who is 48 years old, has been diagnosed with breast cancer, had a lumpectomy & is now starting chemo.  Before the breast cancer she unfortunately was on several other medicines.

Which included: 1) Levethroid 200mg (thyroid); 2)Advair (1 puff) (2x/day - asthma); 3) Ranitidine 300 mg (asthma); 4) Singular 10mg (asthma); 5) Allegra 180mg (1or 2/day - asthma); 6) Actos 30mg (diabetes); 7) Glucovance 5/500mg (2x/day - diabetes); 8) Atacand 32 mg (high blood pressure); 9) Effexor XR 150mg (depression); 10) Omerprazok 20mg (hietal herna); 11) Pravocchol 40mg(cholesterol); 12) Flonase (2 squirts ea. Side); 13) Tricor 54mg(triglicorydes)

With chemo she is on the following drugs:
14) 5-Fluorouracil; 15) Cytoxan; 16) Adriamycin

And for anti-nausea she is taking:
17) Zofran; 18) Tigan

We have two questions:
1) Zofran says it suppress seratonin levels, Effexor XR says it increases seratonin relative to depression.  Obviously these two drugs work on different "parts or areas" of the body.but are these drugs interacting negatively on each other?  Is this a concern?

2) All total she is on 18 medications.  I have heard references that once a person is on more then 5 medications, interactions between drugs becomes a concern.  I have ask her family physician if there was a concern regarding the 13 medications my wife was on before cancer was found and he was not concerned. In addition, we ask In addition, we ask the Oncologist if there was a concern with all these medications,he also said no.  Frankly, I concerned can you give us your opionion?

[CCF-RN,MSN-JS]

Dear hopeloghome, I did not find any documented interactions between the chemotherapy drugs that have been prescribed and the other medications that you have listed.  It is always wise to keep your physicians informed of any changes in your medications.