Why does using MAOI inhibitors react badly with most medications that come out?

MAO-I can be taken safely with most medications. It is only certain classes of medication. Combined use of non-selective MAO inhibitors or MAO-A inhibitors and serotonergic drugs, such as SSRIs or MDMA and other phenylethylamines, is likely to lead to serotonin syndrome. Serotonin syndrome can also occur, when combining MAOIs with certain opioids such as meperidine. However, other analgesics as morphine and codeine have been used safely with MAOIs.

see http://en.wikipedia.org/wiki/Serotonin_syndrome for more information.

MAO's break down into a chemical called tyramine. Tyramine is a byproduct of many kinds of foods and other medication. If taken with these other foods or meds, you could have a stroke, heart attack, and dangerously high blood pressure.MAO's work well for some people, and they have been taking them for a long time. Many doctor's are uncomfortable when it comes to switching from something that is working for the patient.