Association of adverse effects with high serum posaconazole concentrations.

Posaconazole therapeutic drug monitoring (TDM) is widely utilized to assess therapeutic efficacy and safety; however, clinical effects of very high serum concentrations are unknown. A retrospective review of 90 patients receiving posaconazole for treatment or prophylaxis of invasive fungal infections with serum concentrations ≥3000 ng/mL from 1/1/2019 to 4/30/2021 evaluated the incidence and type of adverse drug reactions (ADRs). Symptomatic ADRs were very common in patients with posaconazole concentrations of ≥5000 ng/mL and 3000-4999 ng/mL (80% vs. 58.8%; P = 0.31). Posaconazole TDM should be performed for both treatment and prophylaxis indications and dose decrease for serum concentrations >3000 ng/mL should be considered.

Drug level monitoring is commonly used to evaluate appropriate dosing and effectiveness of posaconazole, a medication used to treat fungal infections. Patients with high levels commonly had side effects. Posaconazole monitoring should be completed, and doses reduced when levels are high.

Breed, smaller weight, and multiple injections are associated with increased adverse event reports within three days following canine vaccine administration.

OBJECTIVE: To evaluate patient and vaccine factors associated with adverse events (AEs) recorded within 3 days of vaccine administration in a large cohort of dogs. ANIMALS: 4,654,187 dogs vaccinated in 16,087,455 office visits in a 5-year period at 1,119 hospitals of a corporate practice. METHODS: Electronic medical records of dogs vaccinated between January 1, 2016, and December 31, 2020, were searched for diagnoses of possible AEs recorded within 3 days of administration of vaccines without concurrent injectable heartworm preventative. Patient risk factors (age, sex, breed, and weight) and number and type of vaccine were extracted from records. ORs (and 95% CIs) for risk factors were estimated via multivariable logistic regression mixed models with patient as a random effect. RESULTS: AEs were recorded following 31,197 vaccination visits (0.19%, or 19.4/10,000 visits). Reported AE rates increased from 1 to 4 vaccines administered and among individual vaccines were greatest for rabies vaccine. AE rate was generally inversely related to body weight, with largest rates in dogs ≤ 5 kg. The largest AE rates were noted in French Bulldogs and Dachshunds (ORs > 4 compared to mixed-breed dogs). CLINICAL RELEVANCE: Risk factor information can be used to update vaccination protocols and client communication. Breed differences may indicate genetics as the primary risk factor for adverse vaccine reactions following vaccinations.

Perception and usage of short-term prednisone and prednisolone in dogs.

BACKGROUND: Corticosteroids are widely used with low rates of reported side effects and a broad level of comfort in the hands of most veterinarians. With a low side effect reporting level of < 5% and high level of comfort there may be complacency and underestimation of the impact side effects of corticosteroids may have on a pet and pet owner. OBJECTIVE: The objective of this clinical study was to describe the experience and perception of an owner who administered anti-inflammatory doses of oral prednisolone and prednisone to their dog for up to 14 days. We hypothesized dogs receiving anti-inflammatory doses of prednisone and prednisolone would experience much greater rates of side effects by day 14 then reported in current literature. ANIMALS: There were 45 dogs initially enrolled in the study. RESULTS: At each study point, 31 owners provided results. On day 5, 74% (23/31) reported at least 1 change in their dog's behavior including polyuria, polydipsia, polyphagia, polypnea and/or increased vocalization, with 11 individuals (35%) reporting these changes greatly increased. On day 14, 90% of owners (28/31) reported at least 1 change in their dog's behavior including polyuria, polydipsia, polyphagia, and/or polypnea as the most common changes noted. Overall, 61% (19/31) of owners reported an increase in filling of the water bowl over baseline and one-third (11/31) of pet owners reported cleaning up urinary accidents for pets who had been continent prior to the start of the study. Pet owner steroid satisfaction remained high through day 14 at 4.5/5 (1 = very unsatisfied, 5 = very satisfied). CONCLUSION: This study highlights the impact short term anti-inflammatory doses of prednisone or prednisolone have on dog behaviour and confirms our hypothesis that by day 14, 90% of dogs experienced one or more behaviour changes, with polyuria and polydipsia most commonly reported. Adverse events were noted regardless of starting dosage or regimen. Although most pet owners expressed satisfaction with steroid treatment due to its high efficacy, 70% would select a more costly treatment if that treatment had fewer side effects.

The safety of rush immunotherapy in the management of canine atopic dermatitis-230 cases.

BACKGROUND: The duration of the induction phase of allergen-specific immunotherapy conventionally is a period of several weeks, during which the volume of an allergen solution, administered by injection, is gradually increased until the maintenance dose is reached. In rush immunotherapy (RIT), the induction period is abbreviated to achieve a faster improvement in clinical signs of atopic dermatitis (AD) compared to conventional immunotherapy. OBJECTIVE: The aim of this retrospective study was to evaluate the safety of RIT in 230 dogs with AD and report any adverse effects (AE). ANIMALS: Two hundred thirty client-owned dogs. MATERIALS AND METHODS: Medical records of dogs receiving RIT between 2012 and 2021 were analysed and observed AE were investigated. All dogs underwent RIT following a protocol of subcutaneous allergen extract injections, given hourly with an incrementally increasing volume from 0.1 to 1.0 mL. RESULTS: Adverse effects were documented in 6 of 230 (2.6%) dogs. Five of these dogs (2.2%) showed mild gastrointestinal signs (1 of 5 vomiting, 4 of 5 diarrhoea) and one patient an increase in body temperature by 1.5°C. These occurred at different stages of the RIT protocol. All AE were graded as mild and self-limiting. CONCLUSIONS AND CLINICAL RELEVANCE: Based on these data, supervised RIT in dogs appears to be a safe procedure to achieve the maintenance dose of allergen immunotherapy earlier with infrequent and mild AE.

Application of machine learning models to animal health pharmacovigilance: A proof-of-concept study.

Machine learning (ML) models were applied to pharmacovigilance (PV) data in a two-component proof-of-concept study. PV data were partitioned into Training, Validation, and Holdout datasets for model training and selection. During the first component ML models were challenged to identify factors in individual case safety reports (ICSRs) involving spinosad and neurological and ocular clinical signs. The target feature for the models were these clinical signs that were disproportionately reported for spinosad. The endpoints were normalized coefficient values representing the relationship between the target feature and ICSR free text fields. The deployed model accurately identified the risk factors "demodectic," "demodicosis," and "ivomec." In the second component, the ML models were trained to identify high quality and complete ICSRs free of confounders. The deployed model was presented with an external Test dataset of six ICSRs, one that was complete, of high quality, and devoid of confounders, and five that were not. The endpoints were model-generated probabilities for the ICSRs. The deployed ML model accurately identified the ICSR of interest with a greater than 10-fold higher probability score. Although narrow in scope, the study supports further investigation and potential application of ML models to animal health PV data.

Current per- and polyfluoroalkyl substance (PFAS) research points to a growing threat in animals.

Per- and polyfluoroalkyl substances (PFAS) are man-made chemicals that are colorless, odorless, and oil and water repellent. Their widespread use in manufacturing and industrial processes has resulted in environmental contamination found across the world. Exposure to PFAS can lead to a variety of adverse human health outcomes such as increased cholesterol, liver damage, immune suppression, and disruption of endocrine and reproductive systems. Exposure to this family of chemicals is considered a significant public health threat. Though nearly every human and animal around the world has been exposed, most of what is known regarding health effects and toxicological processes of PFAS in animals stems from human epidemiological and laboratory animal studies. Discoveries of PFAS contamination on dairy farms and concerns for companion animals have increased interest in PFAS research related to our veterinary patients. In the limited studies published to date, PFAS has been demonstrated in serum, liver, kidneys, and milk of production animals and has been linked to changes in liver enzymes, cholesterol levels, and thyroid hormones in dogs and cats. This is further addressed in the companion Currents in One Health by Brake et al, AJVR, April 2023. There is a gap in understanding the routes of exposure, absorption of PFAS, and adverse health effects among our veterinary patients. The purpose of this review is to summarize the current literature on PFAS in animals and discuss the implications for our veterinary patients.

Veterinarian COVID-19 vaccine uptake was widespread, but safety and efficacy concerns held some back: descriptive results from a survey of AVMA members' perceptions of COVID-19.

OBJECTIVE: Assess COVID-19 vaccine uptake among veterinarians and describe unvaccinated veterinarians' perceptions of COVID-19 disease and vaccines. SAMPLE: 2,721 (14%) of 19,654 randomly sampled AVMA members. PROCEDURES: A survey of AVMA members was conducted between June 8 and June 18, 2021. Information was collected on COVID-19 experience, vaccination intention, and perceptions of COVID-19 disease and vaccines. RESULTS: A total of 2,721 AVMA members completed the survey. Most respondents reported receiving a COVID-19 vaccine (89% [2,428/2,721]). Most unvaccinated respondents disagreed with concerns about contracting (67% [196/292]) or being harmed by (65% [187/287]) COVID-19 but agreed with concerns about short- (79% [228/290]) and long-term (89% [258/289]) side effects of COVID-19 vaccines. Over 91% (268/292) did not agree that COVID-19 vaccine benefits outweigh the risk. Although 83% (244/293) of unvaccinated respondents reported being unlikely to get a COVID-19 vaccine, 47% (137/291) agreed they would be more likely if they knew people vaccinated without serious side effects. Perceptions of COVID-19 disease severity and susceptibility, beliefs about COVID-19 vaccine benefits, and barriers and facilitators to COVID-19 vaccination varied with vaccination intention. CLINICAL RELEVANCE: Results of the AVMA survey suggested that COVID-19 vaccination was widespread among veterinarians in June 2021. Understanding unvaccinated respondents' health beliefs about COVID-19 and COVID-19 vaccines may facilitate veterinarian vaccination participation. Veterinarians who abstained from COVID-19 vaccination cited concerns about the safety, efficacy, and necessity of COVID-19 vaccines. Our results suggested that demonstrating vaccine safety and a favorable risk-to-benefit ratio of vaccination may help reduce vaccine hesitancy and increase uptake of COVID-19 vaccines among veterinarians.

DrugCentral 2023 extends human clinical data and integrates veterinary drugs.

DrugCentral monitors new drug approvals and standardizes drug information. The current update contains 285 drugs (131 for human use). New additions include: (i) the integration of veterinary drugs (154 for animal use only), (ii) the addition of 66 documented off-label uses and iii) the identification of adverse drug events from pharmacovigilance data for pediatric and geriatric patients. Additional enhancements include chemical substructure searching using SMILES and 'Target Cards' based on UniProt accession codes. Statistics of interests include the following: (i) 60% of the covered drugs are on-market drugs with expired patent and exclusivity coverage, 17% are off-market, and 23% are on-market drugs with active patents and exclusivity coverage; (ii) 59% of the drugs are oral, 33% are parenteral and 18% topical, at the level of the active ingredients; (iii) only 3% of all drugs are for animal use only; however, 61% of the veterinary drugs are also approved for human use; (iv) dogs, cats and horses are by far the most represented target species for veterinary drugs; (v) the physicochemical property profile of animal drugs is very similar to that of human drugs. Use cases include azaperone, the only sedative approved for swine, and ruxolitinib, a Janus kinase inhibitor.

Adverse event classification and signal detection of data from the customer service and pharmacovigilance of a multinational veterinary pharmaceutical company.

The pharmacovigilance of a veterinary company may include the analysis of spontaneous reports of adverse events (AE) related to its products. The present study developed an AE classification flowchart to analyze AE notified to the customer service and pharmacovigilance department of a multinational veterinary pharmaceutical company in Brazil. The product-AE binomials using the flowchart were characterized in terms of their frequencies and subsequently, three signal detection models were used: Reporting Odds Ratio, Bayesian confidence propagation neural network, and Gamma Poisson Shrinker. The signals detected with the three methods were classified according to their intensity, always with the most intense signal in the first position. Among the signals detected by the three methods, the positions of each signal were summed to obtain an aggregated classification that considered the results of the three methods and allowed a serial interpretation. Among the 531 reports, 20 types of AE; 88 product-AE binomials were identified. From the total of reports, seven were signs identified by the three methods. The classification of AE following explicit criteria and the combined use of more than one signal detection method enhances spontaneous-reports-based pharmacovigilance.

UK veterinary professionals' perceptions and experiences of adverse drug reaction reporting.

BACKGROUND: Spontaneous reporting of suspected adverse drug reactions (ADRs) is the cornerstone of pharmacovigilance. Despite this, it is believed that there is significant under-reporting in the veterinary setting. Low reporting rates delay marketing authorisation holders (MAHs) and regulators taking mitigating action in the case of safety concerns. METHOD: We designed a survey to explore the perceptions, attitudes and experiences of UK veterinary professionals towards ADR reporting. The survey was advertised widely through conventional and social media and at several conferences. RESULTS: In total, 260 respondents completed the survey, including 210 veterinary surgeons, 49 veterinary nurses and one suitably qualified person. Respondents generally understood the need to report ADRs. The main barrier to reporting was the suspected ADR being well known, and the most popular potential facilitator identified was the ability to report via the practice management system. Facilitation via education in the form of a pharmacovigilance themed continuing professional development event was particularly popular among veterinary nurses, who reported time as being less of a barrier to reporting than their veterinary surgeon counterparts. CONCLUSIONS: Our findings suggest that technological interventions to facilitate reporting and empowerment of veterinary nurses to report through a tailored training event should be explored further.

Glucocorticoids, Cyclosporine, Azathioprine, Chlorambucil, and Mycophenolate in Dogs and Cats: Clinical Uses, Pharmacology, and Side Effects.

The treatment of immune-mediated disease in dogs and cats continues to evolve as new therapies are adapted from human medicine. Glucocorticoids remain the first-line treatment followed by second-line therapies including cyclosporine, azathioprine (dogs), chlorambucil, or mycophenolate. Second-line therapies are introduced due to the patient's lack of response or intolerable effects to glucocorticoids or may be introduced early in the disease treatment due to the patient's severe life-threatening clinical presentation. The goals of immunosuppressive treatment are to achieve disease remission while minimizing drug side effects. Ultimately, gradual drug tapering to the lowest dose to maintain disease remission or successful drug withdrawal.

Successful management and recovery of a dog with immune-mediated thrombocytopenia following vincristine overdose.

OBJECTIVE: To describe the management and outcome of a dog following a 10-fold dosing error of vincristine. CASE SUMMARY: A 2-year-old neutered female Toy Fox Terrier presenting for immune-mediated thrombocytopenia was administered an accidental overdose of vincristine (0.2 mg/kg [2.71 mg/m2 ]). The dog was managed for severe gastrointestinal signs, neutropenia, and neurological consequences secondary to the overdose. Neurological signs included diffuse muscle tremors, limb hyperextension, and myalgia during the dog's hospitalization. Medical management consisted of aggressive supportive care in addition to novel strategies, including folinic acid, glutamic acid, and Tbo-filgrastim. The dog was discharged from the hospital after 12 days of hospitalization and recovered completely within a month of the overdose with no lasting consequences. NEW OR UNIQUE INFORMATION PROVIDED: This is the first report of the successful management of severe vincristine overdose in a dog. Therapy included the use of Tbo-filgrastim, folinic acid, and glutamic acid along with aggressive supportive care.

Pharmacokinetics and tolerance of repeated oral administration of 5-fluorocytosine in healthy dogs.

BACKGROUND: 5-fluorocytosine is a pyrimidine and a fluorinated cytosine analog mainly used as an antifungal agent. It is a precursor of 5-fluorouracil, which possesses anticancer properties. To reduce systemic toxicity of 5-fluorouracil during chemotherapy, 5- fluorocytosine can be used as a targeted anticancer agent. Expression of cytosine deaminase by a viral vector within a tumor allows targeted chemotherapy by converting 5-fluorocytosine into the cytotoxic chemotherapeutic agent 5-fluorouracil. However, little is known about the tolerance of 5-fluorocytosine in dogs after prolonged administration. RESULTS: In three healthy Beagle dogs receiving 100 mg/kg of 5-fluorocytosine twice daily for 14 days by oral route, non-compartmental pharmacokinetics revealed a terminal elimination half-life of 164.5 ± 22.5 min at day 1 and of 179.2 ± 11.5 min, after 7 days of administration. Clearance was significantly decreased between day 1 and day 7 with 0.386 ± 0.031 and 0.322 ± 0.027 ml/min/kg, respectively. Maximal plasma concentration values were below 100 µg/ml, which is considered within the therapeutic margin for human patients. 5-fluorouracil plasma concentration was below the limit of detection at all time points. The main adverse events consisted of depigmented, ulcerated, exudative, and crusty cutaneous lesions 10 to 13 days after beginning 5-fluorocytosine administration. The lesions were localized to the nasal planum, the lips, the eyelids, and the scrotum. Histological analyses were consistent with a cutaneous lupoid drug reaction. Complete healing was observed 15 to 21 days after cessation of 5-fluorocytosine. No biochemical or hematological adverse events were noticed. CONCLUSIONS: Long term administration of 5-fluorocytosine was associated with cutaneous toxicity in healthy dogs. It suggests that pharmacotherapy should be adjusted to reduce the toxicity of 5-fluorocytosine in targeted chemotherapy.

Cutaneous adverse drug reaction in a dog following firocoxib treatment.

A 9-year-old intact female toy poodle was presented with oedema around the neck, including pus and cutaneous necrosis, 2 days after starting firocoxib treatment and placement of a cervical collar for intervertebral disc disease. Cytology of the pus revealed predominantly mature neutrophils with fewer macrophages and lymphocytes, indicating sterile inflammation. Although a skin biopsy could have provided more diagnostic information, it was not performed at presentation. Firocoxib treatment was discontinued, and immunosuppressive therapy including cyclosporine was initiated, which significantly alleviated the skin lesions. The dog recovered fully in 7 weeks. The final diagnosis was a possible cutaneous adverse drug reaction to firocoxib based on history, clinical signs and response to therapy.

Ceftiofur Side Effect in a Mare-Case Report.

Adverse drug reactions in horses are rare. The antimicrobials are in the list of the most common drugs associated with reaction in horses. The aim of this report is to describe the clinical presentation of an adverse drug reaction after the intramuscular administration of ceftiofur hydrochloride. A 5-year-old crioulo broodmare at one day postpartum presented signs of difficulty to walk, positive pulse in the four limbs, and heart rate of 80 beats per minute (bpm), with a history of fighting with another mare. The clinical suspicions were rhabdomyolysis and laminitis. Initially a dose of flunixin meglumine was administrated intravenous to prevent an endotoxemia. On the same day, the blood collection showed an elevated number of white blood cells, predominantly neutrophils and monocytes. An antimicrobial treatment with ceftiofur hydrochloride at a dose of 2.2 mg/kg intramuscular was applied. At the first day, the mare does not show signs of drug side effect. However, 24 hours later, in the second application, the patient presents incoordination, dizziness, and loss of equilibrium. At the same time, dexamethasone was administrated. The signs were reverted, and the mare was normal after the reaction. The treatment with ceftiofur was changed to enrofloxacin, and the animal had a complete recovery. These drug reactions are not common in the routine of equine clinical practitioners, but they cause a great preoccupation for the owner and the veterinarian.

[Vaccinovigilance: Reports of adverse reactions in the year 2019]. / Vaccinovigilance: Gemeldete unerwünschte Wirkungen immunologischer Tierarzneimittel im Jahr 2019.

INTRODUCTION: The registration of adverse events after the use of immunological veterinary medicinal products (IVMP) is the aim of the vigilance reporting system in Switzerland. Adverse events comprise suspected adverse reactions and lack of expected efficacy. Since the Institute of virology and immunology (IVI) is the competent authority for the regulation of immunological VMP in Switzerland, the reporting system is administrated by the IVI. In 2019, 137 reports concerning authorized immunological VMP were received (15% less compared to 2018). While most of the reports were submitted by the marketing authorization holders (56%), practicing veterinary surgeons contributed to the reporting system, too (40%). This corresponds to an increase of 22% of reported adverse events by the practicing veterinary surgeons compared to the previous year. Private persons (4%) submitted five reports. In comparison to 2018, in 2019 79% of the adverse events were reported by marketing authorization holders and 18% by veterinarians. Dogs (55%) and cats (20%) were mainly affected. Further reports were related to cattle (13%) and horses (5%). Recently, the numbers of reports concerning dogs (+12%) and cats (+4%) have considerably increased. Most of the reports were based on the application of vaccines against canine distemper, hepatitis, parvovirosis and parainfluenza in combination with leptospirosis in dogs as well as cat flu and feline panleukopenia in cats. In 34% of the submitted cases, the causality assessment between the vaccination and the reaction described was evaluated as probable.

INTRODUCTION: L'enregistrement des effets indésirables après utilisation de ­médicaments vétérinaires immunologiques est l'objectif du système de notification de vigilance en Suisse. Les effets indésirables comprennent les effets indésirables suspectés et le manque quant à l'efficacité attendue. L'Institut de virologie et d'immunologie (IVI) étant l'autorité compétente pour la réglementation des produits vétérinaires immunologiques en Suisse, le système de déclaration est administré par l'IVI. En 2019, 137 rapports concernant des produits vétérinaires immunologiques autorisées ont été reçus (15% de moins par rapport à 2018). Alors que la plupart des rapports ont été soumis par les titulaires de l'autorisation de mise sur le marché (56%), les vétérinaires en exercice ont également contribué au système de déclaration (40%). Cela correspond à une augmentation de 22% des effets indésirables rapportés par les vétérinaires en exercice par rapport à l'année précédente. Des particuliers (4%) ont soumis cinq rapports. Par rapport à 2018, en 2019, 79% des effets indésirables ont été signalés par les titulaires d'AMM et 18% par des vétérinaires. Les chiens (55%) et les chats (20%) ont été principalement concernés. D'autres rapports concernaient des bovins (13%) et des chevaux (5%). Récemment, le nombre de signalements concernant les chiens (+12%) et les chats (+4%) a considérablement augmenté. La plupart des rapports étaient basés sur l'application de vaccins contre la maladie de Carré, l'hépatite, la parvovirose et la parainfluenza en association avec la leptospirose chez le chien ainsi que contre la grippe et la panleucopénie féline chez le chat. Dans 34% des cas soumis, l'évaluation de la causalité entre la vaccination et la réaction décrite a été jugée probable.

Probable cutaneous adverse drug reaction due to a cannabidiol-containing hemp oil product in a dog.

BACKGROUND: Cannabidiol (CBD) in hemp oil has become a widely used product in veterinary medicine. To date, there have been no reports of cutaneous adverse events associated with CBD-containing oil in the veterinary literature. CLINICAL SUMMARY: A 4-year-old castrated male Labrador retriever presented with pad sloughing and rapidly progressive cutaneous and mucosal ulceration within five days of administering an oral CBD oil product. Histopathological findings in combination with cutaneous signs were consistent with Stevens-Johnson syndrome. All lesions completely resolved after discontinuation of the hemp oil in addition to a 12 day course of cephalexin and prednisone. Given the lack of alternative causes including other medications, an adverse drug event was deemed probable according to the Naranjo algorithm. CONCLUSIONS AND CLINICAL IMPORTANCE: To the best of the authors' knowledge, this is the first report of suspected cutaneous adverse drug reaction to a CBD-containing hemp oil product.

Drug dose and drug choice: Optimizing medical therapy for veterinary cancer.

Although novel agents hold great promise for the treatment of animal neoplasia, there may be room for significant improvement in the use of currently available agents. These improvements include altered dosing schemes, novel combinations, and patient-specific dosing or selection of agents. Previous studies have identified surrogates for "individualized dose intensity,", for example, patient size, development of adverse effects, and pharmacokinetic parameters, as potential indicators of treatment efficacy in canine lymphoma, and strategies for patient-specific dose escalation are discussed. Strategies for treatment selection in individual patients include conventional histopathology, protein-based target assessment (eg, flow cytometry, immunohistochemistry, and mass spectrometry), and gene-based target assessment (gene expression profiling and targeted or global sequencing strategies). Currently available data in animal cancer evaluating these strategies are reviewed, as well as ongoing studies and suggestions for future directions.

Breed is associated with the ABCB1-1Δ mutation in Australian dogs.

OBJECTIVE: The ABCB1 gene encodes P-glycoprotein (P-gp), a cellular membrane pump. One functional mutation that leads to expression of a less functional form of P-gp, ABCB1-1Δ, has been described in dogs. Individuals with this mutation can have severe adverse reactions to common veterinary pharmaceuticals that are known substrates of this pump. We investigated the detection of this mutation in samples submitted to two Australian diagnostic laboratories. METHODS: A total of 4842 dogs across 27 breeds were tested for the ABCB1-1Δ mutation from buccal swabs or EDTA blood using standard PCR, multiplex PCR, or genotyping chip. Statistical analysis was applied to determine the proportions and odds ratios of the ABCB1-1Δ mutation in herding breeds compared with non-herding breeds. RESULTS: The ABCB1-1Δ mutation was detected in nine breeds. The most commonly affected breeds were collies, Australian shepherds, white Swiss shepherds, and Shetland sheepdogs. Of 32 dogs in 18 non-herding breeds tested, one cocker spaniel and one labradoodle were positive for the mutation, both heterozygous. CONCLUSION: The most frequently affected breeds for ABCB1-1Δ mutation are the collie, Australian shepherd, white Swiss shepherd and Shetland sheepdog. As the mutation is associated with an increased incidence of adverse reactions to commonly used pharmaceuticals, veterinarians need to be aware of the breeds at most risk of carrying this mutation and consider testing these individuals prior to administering these medications.