Duplicate Content Issue

Hey
I know this question has been asked many times, but I can’t really find a clear answer.
I have a doctors directory website in which some of them happen to work in 2 or even 3 different locations, so they would be listed 2 or 3 times in the same category but with different address.
Examples:

http://yourmedic.co.uk/listings/stefan-borowy/
http://yourmedic.co.uk/listings/msc-stefan-borowy-2/
http://yourmedic.co.uk/listings/msc-stefan-borowy-3/

They also happen to have more than one specialities so they are listed in 2 or 3 different categories. However if you click the listing, url is the same for both categories.

First 2 example from the top of each category
http://yourmedic.co.uk/listings/category/gynecologist/
http://yourmedic.co.uk/listings/category/obstetrician/

Can anyone tell me if this is considered as duplicate content? and what should i do? Should i set urls as canonical or maybe redirect 301 ?
Thx a lot