In a debilitated animal, I would not give an injectable enrofloxacin orally as the preservatives that you mentioned could be potentially irritating.
But, I have given injectable enro. orally before (under direction of my vet) when we did not have a suitable dilution available. This patient was not very sick, though.
There is a fantastic product that can be used to dilute drugs like enro., it's the same that's used for human medicine (the chalky, white stuff that children's antibiotics often come in fruity flavours). I really cannot remember the name of the product at the moment, but I believe plenty of exotics clinics use this to dilute their drugs so that their patients with tiny body weights (like small birds, mammals and herps) can actually be given measurable doses.
By the way, "2.27" is not a dosage, but nothing more than a number. You need to include a unit, like g/mL or ug/mL for the value to be a dosage 
If you don't mind me asking, what is the issue with the patient?
Christina
www.herptiles.net