Pharmacokinetics of famciclovir and penciclovir in tears following oral administration of famciclovir to cats: a pilot study

Surveillance for feline herpesvirus type 1 mutation and development of resistance in cats treated with antiviral medications

Feline herpesvirus type 1 (FHV-1) commonly causes ocular surface disease in cats and is treated with antiviral medications targeting viral DNA polymerase (UL30/42). Herein, we describe a method to assess the FHV-1 genome for mutation development and to assess the functional impact of mutations, if present. Fourteen shelter-housed domestic cats with FHV-1 ocular surface disease were assigned to one of four treatment groups: placebo (n = 3), cidofovir 0.5% ophthalmic solution (n = 3), famciclovir oral solution (n = 5), or ganciclovir 0.15% ophthalmic solution (n = 3). Swabs were collected before (day 1) and after (day 8) 1 week of twice-daily treatments to isolate viable FHV-1. Viral DNA was extracted for sequencing using Illumina MiSeq with subsequent genomic variant detection between paired day 1 and day 8 isolates. Plaque reduction assay was performed on paired isolates demonstrating non-synonymous variants. A total of 171 synonymous and 3 non-synonymous variants were identified in day 8 isolates. No variants were detected in viral UL23, UL30, or UL42 genes. Variant totals were not statistically different in animals receiving antiviral or placebo (p = 0.4997). A day 8 isolate from each antiviral treatment group contained a single non-synonymous variant in ICP4 (transcriptional regulator). These 3 isolates demonstrated no evidence of functional antiviral resistance when IC₅₀ was assessed. Most (10/14 pairs) day 1 and 8 viral isolate pairs from the same host animal were near-identical. While functional variants were not detected in this small sample, these techniques can be replicated to assess FHV-1 isolates suspected of having developed resistance to antiviral medications.

A review of evidence-based management of infectious ocular surface disease in shelter-housed domestic cats

Infectious ocular surface disease (IOSD) is a common problem in shelter-housed domestic cats and has a widespread negative impact on animal welfare. While the common etiological agents are well-described, addressing IOSD in large groups of animals presents a management challenge to the clinician and logistical challenges to shelter employees. Treatments, diagnostics, and prevention strategies that are effective in privately owned or experimental animals may be impractical or ineffective in the shelter environment. This review article focuses on the relative prevalence of etiological agents in feline IOSD, practical diagnostic testing protocols, prevention strategies, and treatment of IOSD in shelter-housed cats. Discrepancies between experimental laboratory-based studies and clinical trials assessing therapeutics for treatment of feline herpes virus are highlighted. Further high-quality clinical trials are necessary to determine optimal preventative and therapeutic protocols for IOSD in shelter-housed cats.

Evaluation of compounded cidofovir, famciclovir, and ganciclovir for the treatment of feline herpesvirus ocular surface disease in shelter-housed cats

OBJECTIVE

To assess the efficacy of compounded cidofovir, famciclovir, and ganciclovir for the treatment of feline herpesvirus type 1 (FHV-1) ocular surface disease.

ANIMALS STUDIED

132 shelter-housed cats qPCR positive for FHV-1.

PROCEDURES

A masked placebo-controlled study design was utilized. Animals were enrolled in one of four treatment groups: topical ocular placebo + oral placebo (n = 32), compounded cidofovir 0.5% ophthalmic solution + oral placebo (n = 32), compounded famciclovir oral solution (90 mg/kg) + topical ocular placebo (n = 32), and compounded ganciclovir 0.15% ophthalmic solution + oral placebo (n = 36). Cats were treated with each medication twice daily for 7 days and were evaluated on Day 1 and Day 8 using an ocular scoring system, body weight, and qPCR for FHV-1 viral load.

RESULTS

Cidofovir significantly decreased viral load from Day 1 to Day 8 compared with placebo (p = .024). Neither famciclovir nor ganciclovir decreased viral load compared with placebo (p = .14, p = .41). There was no significant improvement of ocular scores for any drug group compared with placebo (p = .62). In all groups, 65%-75% of cats improved from Day 1 to Day 8. Juvenile cats had a significant increase in weight gain compared with placebo for cidofovir (p = .025) and ganciclovir (p = .023). All corneal ulcers in placebo animals failed to heal whereas 77% of ulcers in antiviral group animals healed.

CONCLUSIONS

Topical ophthalmic cidofovir significantly decreased ocular FHV-1 viral shedding and increased weight gain in juvenile cats. Ganciclovir increased weight gain in juvenile cats. Compounded famciclovir demonstrated limited efficacy for the treatment of FHV-1 ocular surface disease in shelter-housed cats.

Drug content on receipt and over time for compounded formulations of famciclovir

OBJECTIVES

The aim of this study was to determine famciclovir content (strength) in compounded formulations and to determine if potency changed over time.

METHODS

Four concentrations of oral oil suspension in three distinct flavors, three concentrations of oral paste, three chew treats and 62.5 mg tablets from one compounding pharmacy were evaluated for famciclovir content. Specific sample preparation procedures were used for each drug formulation prior to determination of famciclovir content through mass spectrometry tandem liquid chromatography. Analysis was performed on arrival from the compounder and on days 7, 14, 28, 56 and 120. Samples were run in triplicate and concentration determined by comparison with a standard curve. Content was considered appropriate if within 90-110% of the labeled concentration.

RESULTS

On arrival from the compounding pharmacy, 5/12 oral oil suspensions of varying concentrations were <90% of the labeled concentration and 3/3 oral pastes were >110%. Famciclovir content in oil suspensions ranged from 72% to 118% of the label value while oral pastes ranged from 95% to 202% of the label concentration over the 120 study days, and all concentrations varied in an unpredictable fashion. Tablets contained 90-110% of the labeled value throughout the study period. Chew treats could not be successfully analyzed.

CONCLUSIONS AND RELEVANCE

This study found substantial variation in famciclovir content in the compounded products evaluated, which, in turn, raises concerns that substandard dosing could result in lack of efficacy or a failed treatment trial. Drug toxicity might also be encountered. Veterinarians must be aware that while compounded medications can improve compliance, they might not deliver the drug dose expected.

In vitro efficacy of ganciclovir against feline herpesvirus type 1 and assessment of ocular tolerability in healthy cats

OBJECTIVES

Feline herpesvirus-1 (FHV-1) is a prevalent cause of ocular disease in cats and limited topical options for treatment currently exist. The first objective of this study was to confirm the efficacy of ganciclovir against FHV-1 in vitro. The second objective was to assess the safety and ocular tolerability of topically applied ganciclovir eye gel (GEG) in healthy cats.

METHODS

FHV-1 was used to infect tissue culture wells covered in maximally confluent Crandall-Rees feline kidney cells prior to the addition of three molarities of ganciclovir (8.9 µM, 17.8 µM and 89 µM) before being incubated for 48 h. Ganciclovir efficacy in vitro was then assessed using standard plaque reduction assay. Commercially available GEG (0.15%) was applied q8h to one randomly chosen eye of four healthy cats for 7 days. Commercially available lubricating eye gel (LEG) was applied to the opposite eye q8h. Complete blood counts (CBCs), blood chemistry panels (CHEM) and urinalysis (UA) were performed on all cats before and after the study period. Ocular lesions were assessed daily using a standardized scheme.

RESULTS

Ganciclovir led to a significant reduction in FHV-1 plaque number, area and diameter at all tested molarities in vitro. The highest molarity assessed (89 µM) caused a 100% reduction in viral plaque number. There was no significant difference in ocular lesion scores between eyes receiving GEG and LEG. Animals remained healthy throughout the study period with CBC, CHEM and UA showing no clinically significant alterations.

CONCLUSIONS AND RELEVANCE

Based on the in vitro results, ganciclovir appears to be effective against FHV-1 in vitro. When applied q8h as a commercial 0.15% gel to a small group of cats with normal eyes, this medication was well tolerated. Taken together, these data suggest this medication warrants further investigation in cats with ocular disease caused by FHV-1.

A Randomized, Placebo-Controlled Clinical Trial of Famciclovir in Shelter Cats with Naturally Occurring Upper Respiratory Tract Disease

Simple Summary

Upper respiratory tract disease (URTD) impacts the health and welfare of shelter cats. Mitigation strategies include stress reduction and population-level approaches; effective treatment plans focus on reducing the clinical signs in cats affected by URTD. This study evaluated the use of famciclovir, an antiviral therapy, in reducing clinical signs in shelter cats with URTD when administered at a target dose range of 40–90 mg/kg twice daily for up to 21 days. Cats were randomized into either a famciclovir treatment group (n = 11) or placebo group (n = 11). Testing for viral pathogen identification was performed at enrollment in the study, and clinical scoring was completed daily to evaluate the severity of signs. With each day of treatment, cats in both groups were less likely to experience worsening clinical scores; however, cats in the famciclovir treatment group had a significantly lower risk of worsening clinical signs with each day compared to the placebo group. Feline herpesvirus, a common pathogen causing URTD, was identified in 11/21 cats. The results of this small study justify the need for further research to determine the utility of famciclovir as part of treatment protocols for improving clinical signs and overall impacts of URTD in shelter cats.

Abstract

Upper respiratory tract disease (URTD) is a clinically relevant infectious disease in shelter cats, with individual and population-level welfare implications. The purpose of this study was to evaluate the effectiveness of famciclovir in reducing clinical signs of URTD in shelter cats during a therapeutic period of up to 21 days. Cats at two Northeastern United States animal shelters with URTD clinical signs were enrolled in a pragmatic, prospective, randomized, placebo-controlled clinical trial. Cats received either famciclovir (n = 11, target dose range 40–90 mg/kg) or placebo (n = 11), administered orally twice daily for up to 21 days with once-daily clinical scoring. At enrollment, conjunctival and oropharyngeal samples were collected for respiratory pathogen identification by RT-PCR. Zero-inflated Poisson regression was used to evaluate the treatment group effects and changes in clinical scoring over time. With each day of treatment, cats in both groups were less likely to experience worsening clinical scores; however, the risk of worsening scores with each day of treatment was significantly less in the famciclovir group compared to placebo (p = 0.006). Feline herpesvirus (FHV-1) DNA was detected in 11/21 cats. The findings justify further pragmatic studies to determine whether famciclovir treatment can contribute to a clinically relevant reduction in URTD morbidity in shelter cats.

Utility of systemic voriconazole in equine keratomycosis based on pharmacokinetic-pharmacodynamic analysis of tear fluid following oral administration

Objective

To clarify the detailed pharmacokinetics (PK) of orally administered voriconazole in tear fluid (TF) of horses for evaluating the efficacy of voriconazole secreted into TF against equine keratomycosis.

Animals studied

Five healthy Thoroughbred horses.

Procedures

Voriconazole was administrated through a nasogastric tube to each horse at a single dose of 4.0 mg/kg. TF and blood samples were collected before and periodically throughout the 24 hours after administration. Voriconazole concentrations in plasma and TF samples were analyzed using liquid chromatography‐electrospray tandem‐mass spectrometry. The predicted voriconazole concentration in both samples following multiple dosing every 24 hours was simulated by the superposition principle.

Results

The mean maximum voriconazole concentrations in plasma and TF were 3.3 μg/mL at 1.5 h and 1.9 μg/mL at 1.6 h, respectively. Mean half‐life in both samples were 16.4 and 25.2 h, respectively. The ratio of predicted AUC_0–24 at steady state in TF (51.3 μg∙h/mL) to previously published minimum inhibitory concentration (MIC) of Aspergillus and Fusarium species was >100 and 25.7, respectively.

Conclusions

This study demonstrated the detailed single‐dose PK of voriconazole in TF after oral administration and simulated the predicted concentration curves in a multiple oral dosing. Based on the analyses of PK‐PD, the simulation results indicated that repeated oral administration of voriconazole at 4.0 mg/kg/d achieves the ratio of AUC to MIC associated with treatment efficacy against Aspergillus species. The detailed PK‐PD analyses against pathogenic fungi in TF can be used to provide evidence‐based medicine for equine keratomycosis.

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

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.

A review of antiviral drugs and other compounds with activity against feline herpesvirus type 1

Feline herpesvirus type 1 (FHV-1) is a common and important cause of ocular surface disease, dermatitis, respiratory disease, and potentially intraocular disease in cats. Many antiviral drugs developed for the treatment of humans infected with herpesviruses have been used to treat cats infected with FHV-1. Translational use of drugs in this manner ideally requires methodical investigation of their in vitro efficacy against FHV-1 followed by pharmacokinetic and safety trials in normal cats. Subsequently, placebo-controlled efficacy studies in experimentally inoculated animals should be performed followed, finally, by carefully designed and monitored clinical trials in client-owned animals. This review is intended to provide a concise overview of the available literature regarding the efficacy of antiviral drugs and other compounds with proven or putative activity against FHV-1, as well as a discussion of their safety in cats.

Controlled release delivery of penciclovir via a silicone (MED-4750) polymer: kinetics of drug delivery and efficacy in preventing primary feline herpesvirus infection in culture

Background

Herpesviruses are ubiquitous pathogens that infect and cause recurrent disease in multiple animal species. Feline herpesvirus-1 (FHV-1), a member of the alphaherpesvirus family, causes respiratory illness and conjunctivitis, and approximately 80% of domestic cats are latently infected. Oral administration of famciclovir or topical application of cidofovir has been shown in masked, placebo-controlled prospective trials to reduce clinical signs and viral shedding in experimentally inoculated cats. However, to the authors’ knowledge, other drugs have not been similarly assessed or were not safe or effective. Likewise, to our knowledge, no drugs have been assessed in a placebo-controlled manner in cats with recrudescent herpetic disease. Controlled-release devices would permit long-term administration of these drugs and enhance compliance.

Methods

We therefore engineered implantable cylindrical devices made from silicone (MED-4750) impregnated with penciclovir, for long-term, steady-state delivery of this drug.

Results

Our data show that these devices release penciclovir with a burst of drug delivery until the tenth day of release, then at an average rate of 5.063 ± 1.704 μg per day through the next 50 days with near zero-order kinetics (in comparison to MED-4750-acyclovir devices, which show the same burst kinetics and average 2.236 ± 0.625 μg/day thereafter). Furthermore, these devices suppress primary infection of FHV-1 in a cell culture system.

Conclusions

The clinical deployment of these silicone-penciclovir devices may allow long-term treatment of FHV-1 infection with a single intervention that could last the life of the host cat.

Ocular manifestations of feline viral diseases

Feline viral diseases are common and cats can be presented with a variety of clinical manifestations. Ocular disease associated with viral pathogens is not unusual, particularly with viruses causing upper respiratory tract disease in cats, such as feline herpesvirus type 1 and feline calicivirus. These agents mainly cause ocular surface disease. Other viruses, such as feline immunodeficiency virus and feline coronavirus, can cause uveitis, while feline leukemia virus can induce ocular lymphosarcoma. This review covers the most common viral pathogens of cats that cause ocular manifestations, the specific features of the ocular diseases caused by these viruses and therapeutic recommendations.