I am not a vet...yet...but I jost wrote a paper on ferret insulinomas
regarding treatment.  Side effects of Diazoxide include anorexia, vomitting,
diarrhea, tachycardia, hematologic abnormalities.... I did not read anywhere
that it causes weakness.  Perhaps the immediate weakness that you are
talking about is due to a persistent hypoglycemia and perhaps the dose of
diazoxide should be increased.  Weakness, ataxia, and lethargy are some of
the clinical signs of hypoglycemia.
 
Diazoxide does directly inhibit insulin secretion but it also stimulates the
beta-adrenergic system, stimulating epinephrine which increases hepatic
glycogenolysis and glucogenesis, and decrease the uptake of glucose by
peripheral cells.
 
If the dose of diazoxide can't be increased, a combination therapy of
prednisone and diazoxide could be tried....then of course there is always
surgery...
[Posted in FML issue 1551]