On Doctoring MEDLINE searches, with reference librarian comments

The question was

"What over-the-counter herbal remedies may have an
adverse reaction with patients currently on prescription medications
and what problems may unexpectedly arise?"

Strategy:

1 :  exp Medicine, herbal/         {549}
2 :  exp Pharmaceutical preparations/ad,ae,me,ct,st,to         {14722}
[Administration & Dosage, Adverse Effects, Metabolism,
Contraindications, Standards, Toxicity]
3 :  1 and 2         {59}
4 :  exp Drug interactions/         {26867}
5 :  3 and 4         {3}
6 :  from 5 keep 1-3          {3}

Reference Librarian comments

Right off the bat I know this is a tricky question. It's easy to
fathom the question, but it will be a difficult search. First of
all, though we don't have much else better to rely on, MEDLINE is
going to disappoint us in "alternative medicine" areas. MEDLINE
indexes 4000 journals and not many of them are publishing articles on
the topic. Also, you couldn't really be expected to know this, but
MEDLINE would prefer that you use SPECIFIC herb-names (e.g., Aloe,
Ginseng, Valerian).

So, I think I might try something like this:

aloe or cayenne or chamomile or chasteberry or echinacea or ephedra
or feverfew or garlic or giner or ginkgo or ginseng or goldenseal or
hawthorn or licorice or thistle or nettle or "passion flower" or
peppermint or "St. John's Wort" or "saw palmetto" or senna or
eleuthero or valerian or "witch hazel"

... and then I'd "AND" that to drug interactions like you did.
Actually, I did this search and I'll copy the strategy I used down
below, at the bottom of this message. (In the middle of doing the
search I learned that I could use the subject-heading "Plant
Extracts" and so I included that also...