Para mientras o Por mientras

From the Spanish Travelogue lesson 10.5 At the Doctors
- Necesito algo para el dolor para mientras. I need something for the pain in the meantime.
- ¿Puede darle algo para el dolor por mientras? Can you give him something for the pain in the meantime?

I was curious to see these phrases one after the other and so I did a quick internet search to see if they were interchangeable or if one was preferred over the other. What came back was neither are correct! Really?!
https://es.answers.yahoo.com/question/index?qid=20110629151430AAEnT4r
 

I would not have thought either, but would have fallen into the trap of trying to translate this literally, saying "Necesito algo para el dolor en el (la) mientras.""

Although, after looking the word up at SpanishDict.com, I suggest:

"Mientras, necesito algo para el dolor." 

My reflex was to say "Mientras tanto". "Mientras" alone would work but you would need to add a dependent phrase: "I need something for the pain while you..."