Most vets know diddly squat about rats.

They drink the antibiotic yes. It is called Tetracycline or Ornacycline, and it available as tabs for birds. You may need to buy about three packages to complete the round of antibiotics, as you are treating two rats, maybe four now.

You add two tabs to the water every day intheir water bottle, making sure you completely cover the bottle with foil so you do not ruin the medication. They should be treated for a full seven days. Even if the symptoms dissapear, they need to have seven days.

You can call your vet and see if he can prescribe some amoxi-drops or clavamox though, it's sweet and your rats will most likely like it.