Impact of concerning excipients on animal safety: insights for veterinary pharmacotherapy and regulatory considerations

OBJECTIVES

Veterinarians and pharmacists are familiar with the efficacy and safety aspects attributed to active pharmaceutical ingredients included in medicines, but they are rarely concerned with the safety of excipients present in medicines. Although generally recognized as safe, excipients are not chemically inert and may produce adverse events in certain animal populations. This review aims to present excipients of concern to these populations and highlight their relevance for rational veterinary pharmacotherapy.

EVIDENCE ACQUISITION

A comprehensive review of the literature about the existence of adverse reactions in animals caused by pharmaceutical excipients was carried out based on an exploratory study. An overview of the correct conditions of use and safety of these excipients has also been provided, with information about their function, the proportion in which they are included in the different pharmaceutical dosage forms and the usual routes of administration.

RESULTS

We identified 18 excipients considered of concern due to their potential to cause harm to the health of specific animal populations: bentonite, benzalkonium chloride, benzoic acid, benzyl alcohol, ethanol, lactose, mannitol, mineral oil, monosodium glutamate, polyethylene glycol, polysorbate, propylene glycol, sodium benzoate, sodium carboxymethylcellulose, sodium lauryl sulfate, sulfites, polyoxyethylene castor oil derivatives, and xylitol. Among the 135 manuscripts listed, only 24 referred to studies in which the substances were correctly evaluated as excipients.

CONCLUSIONS

Based on the information presented in this review, the authors hope to draw the attention of professionals involved in veterinary pharmacotherapy to the existence of excipients of concern in medicines. This information contributes to rational veterinary pharmacotherapy and supports veterinary pharmacovigilance actions. We hope to shed light on the subject and encourage studies and new manuscripts that address the safety of pharmaceutical excipients to the animal population.

Assessing an Exposure Keratopathy Prevention Strategy in Mechanically Ventilated Patients: A Retrospective Study

OBJECTIVE

Patients who are intubated and sedated are at risk for developing exposure keratopathy, which can lead to permanent vision loss. This retrospective study assesses the incidence of exposure keratopathy (EK) in intensive care unit (ICU) patients before and after implementation of an EK Prevention Order Set.

METHODS

At one tertiary care hospital (Bronx, NY), an "Exposure Keratopathy Prevention Order Set" was implemented to ameliorate this risk which included the application of white petrolatum-mineral oil lubricating ointment every 6 hours in both eyes. This retrospective chart review study analyzed the incidence of EK diagnosis before and after implementation of this EK Prevention Order Set. Patients who were on mechanical ventilation at the time of ophthalmology consult request between January 1, 2021, and December 31, 2021, were included. Ophthalmology consult notes of patients with EK diagnosis were reviewed for details regarding the consult request, examination findings, diagnosis, and treatment plan.

RESULTS

There were 247 and 361 ventilated ICU patients before and after the order set, respectively. The number of ophthalmology consults decreased slightly after the order set from 15 of 247 to 20 of 361 ventilated patients. In addition, the rate of EK among ventilated patients decreased from 4.5% (11 of 247 patients over 151 days) to 2.2% (8 of 361 patients over 212 days; P =0.154) with a risk ratio of 0.50 (95% CI 0.20-1.22).

CONCLUSION

The number of patients diagnosed with EK trended down after implementation of the EK Prevention Order Set.

Precorneal retention time of ocular lubricants measured with fluorophotometry in healthy dogs

OBJECTIVE

Determine the precorneal retention time of five different ocular lubricants commonly used in dogs.

ANIMALS STUDIED

Six healthy Beagle dogs (n = 12 eyes).

PROCEDURES

Five ocular lubricants were studied: Artificial Tears Solution® (1.4% polyvinyl alcohol), I-Drop® Vet Plus (0.25% hyaluronate), Optixcare® Eye Lube Plus (0.25% hyaluronate), Systane® Ultra (0.4% polyethylene glycol 400 and 0.3% propylene glycol), and Artificial Tears Ointment® (mineral oil/white petrolatum). Each lubricant was mixed with 10% sodium fluorescein to achieve 1% fluorescein formulations. Following topical administration of 35 mg in each eye, tear fluid was collected with capillary tubes at selected times (0, 1, 5, 10, 20, 30, 40, 50, 60, 90, 120, 180 min) and fluorescein concentrations were measured with a computerized scanning ocular fluorophotometer.

RESULTS

Tear fluorescence was significantly greater with Artificial Tears Ointment® compared with other lubricant formulations from 1 to 20 min post-administration. Median (range) precorneal retention times were significantly different among the 5 lubricants, ranging from 40 minutes (20-90 min) for Artificial Tears Ointment®, 35 min (20-90 min) for Systane® Ultra, 30 min (10-60 min) for I-Drop® Vet Plus, 25 min (10-60 min) for Optixcare® Eye Lube Plus, and 10 min (10-20 min) for Artificial Tears Solution®. Precorneal retention time was significantly lower for Artificial Tears Solution® compared with the other 4 formulations.

CONCLUSIONS

This study established normative data for the retention time of common lubricants on the ocular surface of dogs, which may be used to guide clinicians with their choice of lubricant and frequency of administration.

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.

Topical chemotherapy with mitomycin C in a feline corneal squamous cell carcinoma

Case summary

A 9-year-old cat was presented with a right globe lesion of 6 months’ duration. A large pink elevated mass covering two-thirds of the right cornea was detected. The corneal mass was surgically removed by superficial keratectomy and diagnosed by histopathology as a squamous cell carcinoma (SCC). The surgical procedure led to a relatively transparent cornea, but recurrence was likely. To avoid relapse, 1 month after surgery three cycles of mitomycin C 0.04% eye drops were applied q8h for 15 days on/15 days off. No local or systemic side effects were seen, and no recurrence was detected after 1 year of follow-up. Topical mitomycin C was successfully used as adjuvant local chemotherapy agent and prevented relapses owing to its cytostatic effect.

Relevance and novel information

SCCs are relatively common in feline patients, especially in the non-pigmented extremities of the nose, ears and eyelids, but with the cornea being a rare location. They rarely metastasise and they seldom relapse locally after surgical excision. Surgical-free margins of 2 cm are advisable to prevent relapses. Corneal tumours are rare, as the cornea is avascular; corneal transparency is essential to assure clear vision. In corneal SCC this margin is impossible to achieve without enucleation. In the present report, surgical removal of the neoplasm was combined with topical administration of the anticancer drug mitomycin C and a good prognosis was obtained. This combined treatment may be an appropriate therapeutic option for feline corneal SCC.

Consider the eye in preventive healthcare - ocular findings, intraocular pressure and Schirmer tear test in ageing cats

OBJECTIVES

Geriatric health screening in cats is highly recommended. However, information about normal and abnormal findings is scarce, especially regarding the eyes of ageing cats. This prospective study examined the influence of the ageing process on vision and ocular structures in older cats.

METHODS

A total of 209 cats (aged 9-24 years) underwent physical examination, vision assessment, slit lamp biomicroscopy and ophthalmoscopy. Systolic blood pressure (SBP) measurement, Schirmer tear test (STT) reading and rebound tonometry were performed. Systemic disease was not a criterion for exclusion.

RESULTS

Vision was good in 157/209 cats (75.1%) and impaired in 52/209 cats (24.9%). Increasing age and the occurrence of vision impairment were not statistically associated ( P = 0.053). Retinal oedema, retinal haemorrhage and/or retinal detachment (19 cats) and glaucoma (12 cats) were the most common findings in vision impaired cats. Increasing age was significantly associated with the occurrence of lenticular sclerosis ( P = 0.01) and attenuated retinal vessels ( P = 0.02). Increasing age and SBP were significantly associated with the occurrence of retinal detachment, haemorrhage and oedema ( P <0.001 each). In cats without evidence of hypertensive ocular damage, younger cats had a tendency for higher SBP values than older cats, although this difference was not significant. Mean intraocular pressure (IOP) was 16.5 ± 5.0 mmHg. Age did not significantly affect the IOP values ( P = 0.54). Mean STT was 15.8 ± 4.8 mm/min. The STT was found to increase with age ( P = 0.025).

CONCLUSIONS AND RELEVANCE

Although vision impairment is not a clinical sign of old age in cats, age-related changes may contribute to vision-threatening diseases. This study contributes to preventive healthcare by examining the influence of the ageing process on vision and ocular structures in older cats.

Density and distribution of feline conjunctival goblet cells

Objectives The objective of this study was to examine the density and distribution of goblet cells (GCs) in the feline conjunctiva and to investigate a potential effect of age and sex on GC density (GCD). Methods Thirty-nine eyes of 21 cats euthanased for reasons unrelated to this study were used. Fixed upper and lower eyelid and bulbar conjunctiva were divided into nasal and temporal regions. The third eyelid was excised and investigated separately. Samples were embedded in paraffin wax; sections were stained with periodic acid-Schiff reaction and analysed with light microscopy. To determine the topographic distribution of GCs, each region was subdivided into the marginal, palpebral and bulbar zone. In each zone 200 epithelial cells, including GCs, were counted. Goblet cell index was defined as a percentage of the epithelial cells. Results The palpebral zone of both eyelids contained significantly ( P <0.001) more GCs (27.5-32.0%) than the marginal or bulbar areas. The highest GCD was found in the nasal palpebral zone of the upper eyelid (32.0%). Marginal and bulbar sites contained fewer numbers of GCs (2.6-10.0%). The lowest GCD was detected in the nasal bulbar zone of the lower eyelid (2.6%). Overall the nasal region contained significantly ( P = 0.036) more GCs than the temporal region, but there was no significant difference in GCD between the upper and lower eyelids. Correlation analysis did not show any effect of age or sex on GC counts. Conclusions and relevance GCD in the palpebral zones and on the anterior surface of the third eyelid was highest; the lowest density was found in the bulbar zones of the lower eyelid and in the marginal zones of both eyelids. Overall, higher GCD was found in the cat than in other species. Age and sex have no effect on GCD.