Also in a Medscape article (free subscription):
Incretin Mimetics: Clinical Use in Combination Therapy -
http://www.medscape.com/viewarticle/519727_print

Excerpt:
"Although exenatide is only approved for use with metformin and/or a
sulfonylurea agent, there is no pharmacologic reason to believe that it
can't be used as monotherapy or in combination with all agents for
treating diabetes, including thiazolidinediones and insulin. Studies
have been completed assessing the combination of exenatide and a
glitazone, and the data have been submitted to the US Food and Drug
Administration. Anecdotally, I have used (off-label) glitazones in
combination with exenatide essentially since the drug was released, and
my patients have done well. The same is true for the combination with
insulin, although there are yet no formal data on this approach to
treatment. The rule of thumb for reducing the dose of any drug that can
cause hypoglycemia when exenatide is added holds true when it is added
to insulin. I generally keep the basal insulin dose the same, but reduce
or eliminate the premeal insulin doses, using the exenatide to enhance
endogenous premeal insulin secretion. Remember, however, that exenatide
does not substitute for insulin in patients with type 1 diabetes;
patients need to have functional beta cells to respond to exenatide.
Patients with type 1 diabetes may benefit from the administration of
pramlintide with their premeal insulin; pramlintide is neuroendocrine
hormone secretion from pancreatic beta cells.[8]"

Note: This exerpt agrees with some of the things Jenny has said about
doctors and prescriptions going beyond FDA approved use.

Frank