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Choose the species
One selection filters the source overview, clinical facts, reports and dose calculator. Literature references are not species-filtered.
Choose one species for its overview and dose calculator, or all species to browse the full evidence.
Source overview
Recorded excerpts for one species. Each dose remains a separate source entry; no regimen is selected.
Choose one species to view its source overview. All-species evidence remains available below.
View full clinical evidence and sources ↓Clinical evidence
Pending clinical review (PROPOSED)Rule-based (RULE_BASED)— applies to the facts and dose entries in this species selection; individual source records retain their own status.
Indications1
Feline herpesvirus-1 (FHV-1) — conjunctivitis, rhinosinusitis, keratitis, dermatitis, ulcerative stomatitis (adjunct)
CatExtra-label (EXTRA_LABEL)1 source record · View provenance
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Indications table · Not applicable · Extra-label (EXTRA_LABEL) · Pending clinical review (PROPOSED) · Rule-based
Original excerpt: Feline herpesvirus-1 (FHV-1) — conjunctivitis, rhinosinusitis, keratitis, dermatitis, ulcerative stomatitis (adjunct) — Extra-label
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Indications table · Not applicable · Extra-label (EXTRA_LABEL) · Pending clinical review (PROPOSED) · Rule-based
Dose regimens2
This calculator performs arithmetic only on the sourced dosing field shown for each result — it does not verify the field's accuracy, does not select which field to use for a patient, and does not replace a veterinarian's order. Not for clinical use. Confirm every result against the primary source before dispensing.
Choose one species above to view its dose calculator.
Adverse effects103
Mild anemia — Reported
CatNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Mild ↑ WBC — Reported
CatNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Well tolerated overall — Limited data but favorable so far
CatNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
These are counts of spontaneously reported events, not proven adverse effects, causal relationships, or incidence rates.
Bars compare report counts within each species; they do not show incidence.
More reportsFewer reportsCat
- Lack of efficacy (bacteria) - NOS7 reports
- Lack of efficacy - NOS7 reports
- Lethargy (see also Central nervous system depression in 'Neurological')6 reports
- Not eating6 reports
- Anaemia NOS5 reports
- Death by euthanasia4 reports
- Dehydration4 reports
- Lethargy (see also Central nervous system depression in Neurological)4 reports
- Neutrophilia4 reports
- Vomiting4 reports
- Wobbliness4 reports
- Abnormal cytology3 reports
Monitoring1
Clinical efficacy; occasional CBC/creatinine with chronic use (neutropenia/renal function)
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Monitoring Parameters · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Contraindications1
Hypersensitivity to famciclovir/penciclovir
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Contraindications & Warnings table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Precautions4
Reduce dose with renal impairment; safety in pregnant cats not studied
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Contraindications & Warnings table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
FHV-1 is resistant to acyclovir and valacyclovir — famciclovir/penciclovir is the preferred oral antiviral option for cats specifically because of this resistance pattern.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Dosing recommendations have evolved significantly (early low-dose studies were ineffective) — use current higher-dose protocols (125 mg/cat q8–12h range), not older low-dose regimens.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
FHV-1 infection is controlled, not cured — recurrence is expected even with lifelong management; set owner expectations accordingly.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Interactions1
Probenecid — ↓ renal excretion of penciclovir → ↑ levels
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Pharmacokinetics5
Bioavailability — Low/variable — ~10% conversion to active penciclovir in cats (Papich)
CatNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Protein binding — Minimal (penciclovir)
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Half-life — Penciclovir ~2–3h (human data); longer intracellularly in infected cells
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Metabolism — Hepatic (aldehyde oxidase) → penciclovir (active)
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Elimination — Renal
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Pregnancy / lactation considerations1
No adverse embryo/fetal effects at very high doses (1000 mg/kg/day) in lab animals. Human FDA category B. Excreted in rat milk — clinical significance in cats unclear.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 499–501; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 309–310 — Pregnancy & Lactation · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Literature references19
References are linked to this drug. Species applicability is not recorded here, so the species filter does not narrow this list. Imported dates do not retain their original precision; confirm dates in the original citation.
- Non-linear pharmacokinetics of penciclovir in healthy cats after single and multiple oral administration of famciclovir.
Study summary not available in the imported record. Open the original citation to review the study.
- Ocular tolerance and tear film pharmacokinetics of 1 % penciclovir cream in cats.
Study summary not available in the imported record. Open the original citation to review the study.
- Penciclovir pharmacokinetics after oral and rectal administration of famciclovir in African elephants (Loxodonta africana) shows that effective concentrations can be achieved from rectal administration, despite lower absorption.
Study summary not available in the imported record. Open the original citation to review the study.
- Antiviral Chemotherapy in Avian Medicine-A Review.
Study summary not available in the imported record. Open the original citation to review the study.
- Evaluation of compounded cidofovir, famciclovir, and ganciclovir for the treatment of feline herpesvirus ocular surface disease in shelter-housed cats.
Study summary not available in the imported record. Open the original citation to review the study.
Sources: PubMed, National Library of Medicine; openFDA, U.S. Food and Drug Administration; Plumb DC. Plumb's Veterinary Drug Handbook. 7th ed. PharmaVet Inc; 2011.
Owner information handout
Plain-language medication information to review with the owner. Open the handout to print it or download a PDF.