-Sniffle-Doodle-
Doctors know which medications mix with others, and which don't. So they would never give you two medications that clash. They'd work with you at low doses until they find a combination that works for you, then will slowly increase the dosage until it works completely for you and makes you feel better.
Now that's just not true. There's a little something called malpractice. If it never happened, there wouldn't be a name for it.
Any psychiatrist worth his or her salt will keep a handbook of drug interactions around. A truly good doctor will go through said book with you by request, though I can't guarantee your shrink will comply enthusiastically. Keep in mind that the Internet is no substitute for the drug interaction handbook or the D.S.M., otherwise we'd all be psychiatrists, now wouldn't we~?