Bute is incredibly toxic to minis, and for some reason a lot of vets out there don't realize this. Not only is there a very narrow safety margin, i.e. you have to be very accurate at dosing them, but there are minis who will have problems even at the correct dose. It should be given at 1mg per pound body weight, which means most minis will get 150 mg to 250 mg--1/4 tablet or less. A lot of vets seem to think the average mini weighs 500 pounds and have owners give 1/2 tablet twice daily. ARGGGG!!! Bute toxicity can cause severe gastric and intestinal ulceration, to the point of perforation and death (in as little as 5-7 days), kidney and liver damage, bone marrow suppression, and lowered blood protein levels. That said, I have used bute on selected minis for laminities, but at a low dose and for short periods of time. For almost everything else I use Banamine (which can also cause problems if dosed too high or too long, but has a wider safety margin) From Plumb's Veterinary Drug Handbook: QUOTE Adverse effects: Horses: oral and GI erosions and ulcers, hypoalbuminemia, diarrhea, anorexia, and renal (KIDNEY) effects. QUOTE Cautious use in both foals and ponies is recommended because of increased incidences of hypoproteinemia (LOW BLOOD PROTEIN LEVELS)and GI ulceration. Foals with a heavy parasite burden or that are undernourished may be more susceptible to development of adverse effects. Phenylbutazone may cause decreased renal blood flow and sodium and water retention, and should be used cautiously in animals with preexisting renal disease or CHF (CONGESTIVE HEART FAILURE). QUOTE The primary concerns with phenylbutazone therapy in humans include its bone marrow effects (agranulocytosis, aplastic anemia), renal and cardiovascular effects (fluid retention to acute renal failure), and GI effects (perforated ulcers). Other serious concerns with phenylbutazone include, hypersensitivity reactions, neurologic, dermatologic (SKIN), and hepatic toxicities. While phenylbutazone is apparently a safer drug to use in horses and dogs than in people, serious adverse reactions can still occur. Toxic effects that have been reported in horses include oral and GI erosions and ulcers, hypoalbuminemia (LOW BLOOD PROTEIN LEVELS), diarrhea, anorexia (LOSS OF APPETITE), and renal effects (azotemia (HIGH LEVELS OF UREA/AMMONIA IN THE BLOOD)). Unlike humans, it does not appear that phenylbutazone causes much sodium and water retention in horses at usual doses, but edema has been reported. In dogs however, phenylbutazone may cause sodium and water retention, and diminished renal blood flow. QUOTE ...acute overdosage with phenylbutazone include, a prompt respiratory or metabolic acidosis with compensatory hyperventilation, seizures, coma, and acute hypotensive crisis. In an acute overdose, symptoms of renal failure (oliguric, with proteinuria and hematuria), liver injury (hepatomegaly and jaundice), bone marrow depression, and ulceration (and perforation) of the GI tract may develop.
