Try to always remember that the -59 modifier is the "unbundling" modifier, which means that procedures that are normally included in one another are being broken down into two separate, identifiable procedures. It is safe to say that a foreign body removal and an injection of zofran aren't normally coded together, so they wouldn't need a -59 modifier. Does that make sense? Injections & infusions are always tricky when done along with another procedure and each situation is different.
Also, always check your CCI edits. I keep a link to them right on my desktop so whenever there is any doubt, I can check there first. But, remember...they are also a quarter behind so any new developments/rules/changes happening in the last quarter will not show in the edits yet. I hope that I have not succeeded in confusing you more. You can always google the use of the -59 modifier and I'm sure you'll get plenty of information that will be helpful. And, if you do a search within all of the posts on this website, they will lead you to a number of posts regarding this modifier. I hope I helped a little!!