The painkiller

Doctor:How can I help you today?

Joe:I am in a lot of pain from my knee surgery last week and I need some stronger medicine .

Doctor:The painkillers I prescribed for you are not working ?

Joe:They only take the edge for an hour or two .After that ,the pain returns .

Doctor:Well,right now you are taking a very mild pain killer .If it's not helping, I can give you something else .

Joe:How about morphine?

Doctor:We only prescribe morphine in extreme cases.There is another good medicine I will prescribe for you .

Joe:Oh, I didn't know that .I'll try whatever you recommend.

34'