In BioShock all versions of this tonic can be equipped together for an increased effect.
In Worlds of Hurt, Medical Expert 2 can be bought at the Gatherer's Garden in the central hub for 50 ADAM.
Medical Expert is also a Tonic available to the player in BioShock 2, but it has a very different effect. Instead of making First Aid Kits more effective, it increases the carry capacity by one. When carrying 6 First Aid kits, the player can choose to swap this tonic for another without dumping the extra First Aid kit. The same goes for EVE Expert.