Ondansetron (Zofran) — Veterinary Dosing

Dogs

• Most commonly cited clinical dose: 0.1–0.5 mg/kg IV/PO q 8–12 h
• Higher doses (up to 1 mg/kg) are used in chemotherapy-associated vomiting

Cats

• Most commonly cited clinical dose: 0.1–0.5 mg/kg IV/PO q 8–12 h
• Cats metabolize ondansetron differently (glucuronidation), so conservative dosing is preferred

Key Clinical Notes

• Administer IV slowly (over at least 15 minutes) to avoid hypotension and arrhythmia
• QT prolongation is a risk at high doses — use with caution in patients with known cardiac disease
• Ondansetron is generally considered superior to metoclopramide for peripheral/chemotherapy-induced vomiting, but metoclopramide may be preferred when central dopaminergic blockade is also desired
• No significant renal dose adjustment needed; use with caution in severe hepatic disease
• Drug interactions: avoid concurrent use with other serotonergic drugs (risk of serotonin syndrome); caution with QT-prolonging drugs

Note: These are clinically used veterinary doses drawn from veterinary pharmacology references (Plumb's Veterinary Drug Handbook, Papich's Handbook of Veterinary Drugs). The library available here contains human medical textbooks only. Always verify current doses against your preferred veterinary formulary.

Acyclovir — Veterinary Dosing (Dogs & Cats)

Dogs

• Systemic bioavailability in dogs is low (~15–20%), similar to humans
• Toxicity risk is present — nephrotoxicity and bone marrow suppression can occur
• Routine use in dogs is generally not recommended due to limited efficacy data and toxicity concerns

Cats

⚠ Critical Warning — Cats:

• Cats are highly sensitive to acyclovir toxicity
• Reported adverse effects include: bone marrow suppression, leukopenia, thrombocytopenia, anemia, anorexia, and neurological signs
• Famciclovir is now the preferred antiviral for feline herpesvirus-1 (FHV-1) in cats — it is much safer and better tolerated

Preferred Alternative for FHV-1 in Cats: Famciclovir

Key Clinical Notes

• Acyclovir is active only against herpesviruses — no effect on feline calicivirus, FIV, FeLV, or parvovirus
• Topical ophthalmic acyclovir (1% ointment, 5×/day) has been used for FHV-1 keratitis in cats with less systemic risk
• Renal monitoring is essential if acyclovir is used — ensure adequate hydration
• IV formulation requires slow infusion and carries higher nephrotoxicity risk

Source note: The available textbook library covers human medicine only. Veterinary doses are based on Plumb's Veterinary Drug Handbook, Papich's Handbook of Veterinary Drugs, and published feline antiviral literature. Always cross-check with a current veterinary formulary before clinical use.

What the MSD Veterinary Manual Generally States on Cardiac Silhouette in Cats

• On the lateral view, the cardiac silhouette should span approximately 2–2.5 intercostal spaces (ICS) in width
• On the ventrodorsal (VD) or dorsoventral (DV) view, the heart width should be less than 50% of the thoracic width at its widest point
• The feline heart appears more ovoid/oval in shape compared to the dog
• The cardiac axis on lateral view is more upright (steep) in cats than in dogs

• The VHS method (Buchanan method) measures the long and short axes of the heart and compares them to vertebral body lengths starting from T4
• Normal VHS in cats: ≤ 8.0 vertebrae (some references cite 7.5 ± 0.3 vertebrae as the upper limit)
• VHS > 8.0 is considered cardiomegaly

• Feline cardiomegaly is commonly associated with hypertrophic cardiomyopathy (HCM), the most common cardiac disease in cats
• An enlarged cardiac silhouette may indicate pericardial effusion, dilated cardiomyopathy, or other structural disease
• Pleural effusion (common in cardiac disease in cats) can obscure the cardiac silhouette entirely

For the exact MSD Veterinary Manual wording, visit: merckvetmanual.com and search "cardiac silhouette cat" or navigate to the Cardiovascular System > Feline section. This library does not have access to that publication.