MSD Manual

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Dosages of Antiviral Drugs

Dosages of Antiviral Drugs

Drug

Preparation

Species, Dose, Route, and Frequency

Indication

Notes

Idoxuridine

0.1% ophthalmic solution or 0.5% ophthalmic ointment

Cats, dogs, horses: 1 drop or ¼-inch strip in affected eye, every 2–3 h for 48 h, followed by every 4–6 h until one week beyond resolution of clinical signs

Ocular herpesvirus (FHV-1, CHV-1, EHV-2) infection

No longer commercially available in the US but may be prepared by compounding pharmacies

Not approved for use in food animals

Potential teratogen: caution for use in pregnant animals; women who are pregnant should avoid handling

Trifluridine

1% ophthalmic solution

Cats, dogs: 1 drop, OU, every 2 h for 2 days, then 3–8 times daily until 1 week beyond resolution of clinical signs; do not use more than 3 weeks to avoid corneal toxicity

Ocular herpesvirus (FHV-1, CHV-1)

Not approved for use in food animals

Caution in patients with glaucoma; may increase intraocular pressure

Women who are pregnant should be cautious when handling

Less well tolerated in cats due to ocular discomfort (stinging) on administration

Vidarabine

3% ophthalmic ointment

0.4- to 1-cm strip, OU, every 5–6 h until one week beyond resolution of clinical signs

Ocular herpesvirus (FHV-1)

No longer commercially available in the US but may be prepared by compounding pharmacies

Not approved for use in food animals

Cidofovir

0.5% ophthalmic solution (compounded from 75 mg/mL injection)

Cats: 1 drop, OU, every 12 h for 5 days

Ocular herpesvirus (FHV-1)

Not approved for use in food animals

Potential teratogen: caution for use in pregnant animals; women who are pregnant should avoid handling or wear protective apparel when handling

Acyclovir

200-mg capsules, 400- or 800-mg tablets, 200 mg/5 mL oral suspension; 50 mg/mL injectable solution or powder for reconstitution; 5% topical ointment

Dogs: 10 mg/kg, PO, every 6 h for 5 days (neonatal CHV-1); 20 mg/kg, IV, every 8 h for 5 days (prophylaxis of canine parvovirus infection)

Horses: 10 mg/kg, IV slowly over 1 h, every 12 h (EHV)

Birds: 80 mg/kg, PO, every 8 h for 7–14 days (Pacheco's disease)

Cats: Contraindicated due to risk of myelosuppression and nephrotoxicity

CHV-1, prophylaxis of canine parvovirus, EHV, Pacheco's disease

Not approved for use in food animals

Poor oral bioavailability in horses; oral administration not recommended

Caution in patients with renal disease and with coadministration potentially nephrotoxic drugs

Valacyclovir

1-g and 500-mg tablets

Horses: 27–40 mg/kg, PO, every 8 h for 2 days, then 18–20 mg/kg, PO, every 12 h for 1–2 weeks

Cats: Contraindicated due to hepatic, renal, and bone marrow toxicity

EHM, EHV-1, EHV-3

Not approved for use in food animals

Contraindicated in cats

Caution in patients with renal disease and with coadministration of nephrotoxic drugs

Ganciclovir

500 mg/vial powder,

0.15% ophthalmic solution

Horses: 2.5 mg/kg, as slow IV bolus, every 8 h for 1 day, then 2.5 mg/kg, as slow IV bolus, every 12 h for maintenancea,b

Dogs: 1 drop, in affected eye, 5 times daily until ulcer resolution; then 1 drop, in affected eye, 3 times daily for 7 days

Cats: 1 drop, in affected eye, every 6 h

Feline herpes keratitis, EHM, ocular CHV-1

Not approved for use in food animals

Potential teratogen: caution for use in pregnant animals; women who are pregnant should avoid handling

Famciclovir

125-, 250- and 500- mg tablets

90 mg/kg, PO, every 8–12 h until 1 week beyond resolution of clinical signsc

FHV-1

Not approved for use in food animals

Zidovudine

10 mg/mL syrup; 10 mg/mL injection; 300-mg tablets; 100-mg capsules

Cats: 5–10 mg/kg, PO or SC, every 12 h

FIV, FeLV

Not approved for use in food animals

Caution in animals with bone marrow suppression; monitor for development of anemia in treated animals, and discontinue use if hematocrit is <20%

Rimantadine

100-mg tablets

Horses: 30 mg/kg, PO, every 12 h

Equine influenza

Prohibited for use in poultry in the US

Not approved for use in food animals

Interferon alfa-2

3 × 106 IU/vial; 30-60 IU/mL oral solution (compounded from commercially available injectable solution)

Cats: 60 IU/cat, PO or buccally once daily, treated 7 days on, 7 days off

FeLV

No oral formulation commercially available in the US, but may be prepared by compounding pharmacies

Not approved for use in food animals

Do not vaccinate animals receiving interferon-alfa

Oseltamivir

30-, 45-, and 75-mg capsules; 30 mg/5 mL oral suspension reconstituted from powder

Horses: 2 mg/kg, PO, every 12 h for 5 days

Dogs: 2 mg/kg, PO, every 12 h for 5 days

Equine influenza, canine parvovirus

Prohibited for use in poultry in the US

Not approved for use in food animals

CRI = constant-rate infusion; EHM = equine herpesvirus myeloencephalopathy; FeLV = feline leukemia virus; FHV-1= feline herpesvirus 1; FIP = feline infectious peritonitis; FIV = feline immunodeficiency virus

aMaxwell LK. Antiherpetic drugs in equine medicine. Vet Clin North Am: Equine practice. 2017;33(1):99–125. doi:10.1016/j.cveq.2016.12.002

bCarmichael RJ, Whitfield C, Maxwell LK. Pharmacokinetics of ganciclovir and valganciclovir in the adult horse. J Vet Pharm Ther 36: 441–9.

cSebbag L, Thomasy SM, Woodward AP, Knych HK, Maggs DJ. Pharmacokinetic modeling of penciclovir and brl42359 in the plasma and tears of healthy cats to optimize dosage recommendations for oral administration of famciclovir. Am J Vet Res. 2016 Aug 1;77(8):833–45. https://doi.org/10.2460/ajvr.77.8.833