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AG 194, Spring, 2007
Veterinary Pharmacology
First Question
A 1,000 pound quarter horse needs to be treated with Bute for a minor lameness after stepping on a stone while trail riding. The Bute dose is 1 gram per 1000# of horse orally every 12 hours for 3 days.
1. What is the generic name (drug name)
for Bute?
Phenylbutazone
2. What category of drug is Bute classified
in?
Nonsteroidal anti-inflammatory drug (NSAID)
3. Is it a controlled substance?
No.
4. What forms(s) does this come in for administration?
Tablets, paste, syringe, injectable, oral powder.
5, What are the possible side effects of
Bute administration in the horse?
(From the Ontario Ministry of Agriculture, Food and Rural Affairs website)
As with many of the NSAIDS, phenylbutazone should not be used in horses
with a history of, or pre-existing hematologic or bone marrow abnormalities
(bleeding disorders) or in animals with pre-existing gastrointestinal
ulcers. Both phenybutazone and its active ingredient, oxyphenbutazone,
are highly bound to plasma proteins and therefore, caution is advised
when using this medication in hors with hypoprteinemia (low blood pressure)
or are undernourished. Phenylbutazone may cause decreased blood flow to
the kidneys and result in sodium and water retention. Therefore, be cautious
with its use in animals with pre-existing renal disease associated with
congestive heart failure. Phenylbutazone and its metabolite, oxyphenbutazone,
cross the placental barrier and are excreted into the milk. Toxic effects
that have been reported in horses include oral and gastrointestinal erosions
and ulcers, hypoalbuminemia, (low blood albumen) diarrhea, anorexia, and
renal effects (azotemia, renal papillary necrosis.)
6. Is Bute used in other veterinary species?
Bute is not frequently used in small animals, although there is a label
claim for use in dogs.
7. How many grams total are necessary for
this horse during treatment time?
Six grams total.
8. What is a major complication if this
drug is injected into a muscle or SQ tissue?
Phenybutazone toxicosis in horses can produce renal insufficiency and
oral, gastric, and colonic ulceration in horses. The colonic ulcers occur
in the right dorsal colon and are the most difficult aspect of phenybutazone
to treat. Colonic ulcers secondary to phenylbutazone toxicity can produce
abdominal pain, marked protein loss, melena (blood in maure) peritonitis,
colonic stricture, or colonic rupture. Dehydration and excessive dosages
are the most important predisposing factors for development of phenyutazone
toxicosis. (An aside -- accidental injection into the artery (e.g. carotid
artery) rather than the vein (e.g. jugular vein) may cause seizures. Of
course, this is an intravenous-related complication.)
9. How would that complication be treated?
Phenybutazone toxicosis would be treated with intravenous fluid therapy.
10. Is Bute a prescription drug?
Yes.
Second Question
A 75 kg 3 year old alpaca male has a swollen prepuce from trauma while fighting another male over the fence. He needs to be treated with an anti-inflammatory, analgesic compound for 3 days. Flunxin meglumine will fit the bill. The dose is 2.5 mg/kg IM every day for 12 hours for 3 days. The injectible drug comes in 10 mg/ml and 20 mg/ml concentrations. The drug costs $50.00 per 100 ml vial.
1. How many ml’s (volume of drug)
is this male going to require at each dose?
75 kg x 2.5 mg/kg = 187.5 mg.
2. Which drug concentration makes the most
sense to use in this alpaca?
20 mg/ml.
3. Why?
According to the above the flunixin will be given intramuscularly. Generally,
larger volumes are given intramuscularly and smaller volumes are given
subcutaneously.
4. What are some complications of an IM
injection on a ruminant?
(Large Animal Clinic Procedures text) IM injections usually cause scar
tissue formation at the injection site. The scar tissue is visible and
causes toughness in the meat, which may extend as much as three inches
from the injection site. There is also the risk of absession. These injection
blemishes must be trimmed out of the meat when it is processed, thus decreasing
the value of the carcass. This has resulted in a tend of avoiding IM injections
into the muscles of that yield valuable cuts of of meat (hindlegs) and
the development of subcutaneously injectable drugs (when possible) to
repleace intramuscular medications.
5. What are other forms of this drug for
administration?
Ibuprofen and Naproxen. Ketoprofen and Carprofen are propionic acid derivatives
structurally related to ibuprofen and naproxen.
6. Would they work as well in this animal?
No
7. Why or why not?
Flunixin has gained popularity not only for its anti-inflammatory effects,
but also for its ability to reduce gastrointestinal pain in horses and
ruminants. Although not approved for food-producing animals (and an alpaca
is not a food producing animal) flunixin appears to be the best analgesic
available for ruminants, providing long, effective relief.
8. What is a common name for flunixin meglumine?
Banamine.
9. What side-effects can be expected from
this class of drug?
It can produce gastrointestinal side effects if given in high doses over
a period of
days.
10. How much does this does cost per day
to the alpaca farmer?
$187.50. (This is if the charge is for a portion of the final vial.)
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