Hemorrhagic diarrhea and mucosal sloughing are commonly seen in dogs with CPV enteritis, and indicate breakdown of the GI
mucosal barrier which can lead to bacterial translocation, endotoxemia, and sepsis. Severe neutropenia often coincides with
the severe enteritis contributing to the risk of systemic sepsis. For these reasons, intravenous broad-spectrum, bacteriocidal
antibiotics are indicated in severely affected puppies. A combination of an aminoglycoside (gentamicin 2.2 mg/kg q 8 h or
amikacin 10 mg/kg q 8 h) with a beta lactam antibiotic (ampicillin 22 mg/kg q 8 h or cefazolin 22 mg/kg q 8 h) provides excellent
coverage against gram negative and anaerobic bacteria which may originate from the gut. Aminoglycosides can cause acute renal
failure and should only be administered after rehydration has been accomplished. Once daily dosing of aminoglycosides (6.6
mg/kg gentamicin or 30 mg/kg amikacin q 24) may minimize renal damage while maximizing bacterial kill because of high peak
and low trough antibiotic concentrations, but the high dose should never be given to dehydrated patients. Urine sediment
should be monitored for the appearance of proteinuria or renal tubular casts, which would warrant discontinuation of aminoglycoside
therapy. Enrofloxacin (5 mg/kg q 12 h) is an alternative choice to the aminoglycosides. It has an excellent gram negative
spectrum, but is not approved for intravenous use and may cause cartilage abnormalities in young growing animals. The author
has not encountered any problems with enrofloxacin when it is diluted 1:1 with saline and administered slowly IV for a relatively
short term (usually 3 - 5 days) in puppies with CPV enteritis. Rapid administration may cause vomiting. The drug can be
discontinued when leukopenia resolves.
Mildly affected dogs with an adequate white blood cell count generally do not require combination antibiotic therapy. Appropriate
antibiotic choices include ampicillin, cephalosporins, or trimethoprim-sulfa in these patients.
Vomiting often decreases when oral intake of food and fluid is discontinued, but in some patients the problem persists and
must be treated to reduce fluid losses and increase patient comfort.
The two antiemetics most commonly used in dogs with CPV enteritis are metoclopramide and chlorpromazine. Metoclopramide is
a gastric promotility drug which can reduce vomiting by stimulating gastric emptying and inhibiting the chemoreceptor trigger
zone. The promotility effect may prevent gastric atony and ileus from occurring in dogs with CPV. Metoclopramide can be
added to the intravenous fluids or administered in a separate drip at a dosage of 1.0 - 2.0 mg/kg/24 hours and given as a
constant rate infusion.
If metoclopramide is ineffective in controlling vomiting, a more effective antiemetic is chlorpromazine. This drug is a phenothiazine
derivative and acts on the emetic center, the chemoreceptor trigger zone, and peripheral receptors to reduce the vomiting
reflex. The recommended dosage is 0.1 mg/kg IV q 4-6 h or 0.2 - 0.5 mg/kg IM q 6 - 8 h as needed. Phenothiazine derivatives
can cause hypotension and systemic vasodilation via their alpha adrenergic blocking effect and should only be given after
the patient is well hydrated.