Page 23 specifically states "starts each game carrying a healing potion"
It's the only piece of soldier's gear mentioned as being carried, instead of just listed.
I would put forth that this wording was intentional, as it could have just as easily been listed as "starts each game with a healing potion"
To me at least, this sounds like an intentional decision in language use to prevent the Apothacary from carrying anything else, at least until the potion is used.
If this is the case, it would prevent the Apothacary from carrying a second potion.
EDIT: I just asked Joe for clarification of this in the FAQ thread.