Oral administration of famciclovir for treatment of spontaneous ocular, respiratory, or dermatologic disease attributed to feline herpesvirus type 1: 59 cases (2006–2013)

Abstract

OBJECTIVE To evaluate outcomes for cats treated with orally administered famciclovir 3 times/d for clinical signs attributed to naturally occurring feline herpesvirus type 1 (FHV-1) infection and to assess variables related to owner satisfaction with the treatment. DESIGN Retrospective case series. ANIMALS 59 client-owned cats. PROCEDURES Medical records were reviewed to identify cats treated for presumed FHV-1 infection from 2006 through 2013 with ≥ 1 follow-up visit. Signalment, duration of clinical signs, prior treatment, examination findings, diagnostic test results, concurrent treatments, and outcome data were recorded. Owners were asked to complete a survey regarding patient- and treatment-related variables. Data were compared between cats that received low (approx 40 mg/kg [18 mg/lb]) and high (approx 90 mg/kg [41 mg/lb]) doses of famciclovir, PO, 3 times/d. RESULTS Patient age ranged from 0.03 to 16 years. Conjunctivitis (51/59 [86%]), keratitis (51 [86%]), blepharitis (19 [32%]), nasal discharge or sneezing (10 [17%]), and dermatitis (4 [7%]) were common findings. Clinical improvement was subjectively graded as marked in 30 (51%) cats, mild in 20 (34%), and nonapparent in 9 (15%). Median time to improvement was significantly shorter, and degree of improvement was significantly greater in the highdose group than in the low-dose group. Adverse effects potentially attributable to famciclovir administration were reported for 10 cats. On the basis of survey responses, most (29/32 [91%]) owners were satisfied with their cat's treatment. CONCLUSIONS AND CLINICAL RELEVANCE Famciclovir at the prescribed dosages was associated with improved clinical signs in cats with presumed FHV-1 infection, and few adverse effects were attributed to the treatment. Further studies are needed to assess whether a famciclovir dosage of 90 versus 40 mg/kg, PO, 3 times/d would result in increased efficacy and shorter treatment time.

Pharmacokinetic modeling of penciclovir and BRL42359 in the plasma and tears of healthy cats to optimize dosage recommendations for oral administration of famciclovir

“…Adverse effects were not associated with the dosage of famciclovir (40 or 90 mg/kg, PO, q 8 h) administered in that study. 9 Therefore, we believe that the urethral obstruction developed by the cat in the present study was a random occurrence rather than an adverse effect associated with famciclovir administration. However, we advise prudence when famciclovir is administered to cats, especially those with impaired kidney function, and further studies are necessary to elucidate the safety of famciclovir in cats.…”

“…This was consistent with results of another study 6 in which administration of famciclovir (90 mg/kg, PO, q 8 h) was an effective treatment for FHV-1 in experimentally infected cats. Likewise, in another study 9 that involved client-owned cats with suspected spontaneous herpetic disease, oral administration of famciclovir at a dosage of 90 mg/kg every 8 hours was more effective than administration of a dosage of 40 mg/kg every 8 hours. Administration of famciclovir at a dose of 90 mg/kg is especially important when the treatment target is an avascular tissue such as the superficial cornea where the drug reaches the tissue via the tear compartment but is also valid when the treatment target is vascularized tissues such as those affected by herpetic blepharitis, conjunctivitis, and vascularized stromal keratitis.…”

“…For example, famciclovir is used as a rescue antiviral drug for human patients with renal toxicosis induced by administration of acyclovir. 32 Furthermore, in a study 9 in which 59 client-owned cats with suspected herpetic disease were treated with famciclovir, only 10 (17%) developed adverse effects potentially attributable to famciclovir; only 1 of those 10 cats had adverse effects referable to the urinary tract (polydipsia without a concurrent decrease in urine specific gravity). Adverse effects were not associated with the dosage of famciclovir (40 or 90 mg/kg, PO, q 8 h) administered in that study.…”

“…[2][3][4][5] In addition, there is mounting evidence that famciclovir is well tolerated and highly effective when administered to cats with experimentally induced herpetic disease 6 or spontaneous disease suspected to be caused by FHV-1. [7][8][9] Like acyclovir and ganciclovir, penciclovir is an acyclic guanosine analog that inhibits herpesviral DNA polymerases. 10 However, penciclovir is poorly absorbed following oral administration in humans, and as a result, famciclovir was formulated as an oral prodrug of penciclovir to enhance bioavailability.…”

In Cats Infected With Feline Herpesvirus Type-1 (FHV-1) Does Treatment With Famciclovir Result in a Reduction of Respiratory and Ocular Clinical Signs?

“…One was that many of the cats had been treated with or were on other medications before and during some of the studies such as in Thomasy et al (2016) and Malik et al (2009). Another was that in some of the studies, the full history of the previous treatments given were unknown or incomplete as some were case reports from multiple sources as in Malik et al (2009).…”