The effect of fluconazole on oral methadone in dogs

Candida auris detected in the oral cavity of a dog in Kansas

Candida auris is an emerging human fungal pathogen, first described in Japan in 2009, and first detected in the United States in 2016. Here, we report the first-ever description of C. auris colonizing a human pet, the first identification of C. auris in a non-human mammal in the United States and the first C. auris isolate from the state of Kansas. While analyzing the oral mycobiome of dogs from a shelter in Kansas, the oral swab from one dog was found to contain C. auris as well as three other fungal species. The presence of C. auris in a dog suggests the possibility of zoonotic transmission to humans. The isolate is a member of Clade IV, which has been found in patients in Chicago and Florida, while Clades I and III are the most prevalent in the United States. The isolate is resistant to fluconazole, terbinafine, and amphotericin B but susceptible to caspofungin, consistent with the drug-resistant characteristics of many human C. auris isolates. The source of C. auris transient colonization in this dog is unknown, and there is no evidence that it was further transmitted to humans, other dogs in the shelter, or pets in its adopted household. Isolation of C. auris from a dog in Kansas has public health implications as a potential emerging source for the zoonotic spread of this pathogenic fungus, and for the development of antifungal resistance.IMPORTANCECandida auris is an emerging fungal infection of humans and is particularly problematic because it is multi-drug resistant and difficult to treat. It is also known to be spread from person to person by contact and can remain on surfaces for long periods of time. In this report, a dog in a shelter in Kansas is found to be colonized with Candida auris. This is the first study to document the presence of Candida auris on a pet, the first to document C. auris presence on a non-human mammal in the United States, and the first to report an isolate of C. auris within the state of Kansas. The presence of C. auris in a pet dog raises the possibility of zoonotic transmission from pets to human or vice versa.

Fungal diversity and drug susceptibility of the oral mycobiome of domestic dogs

The purpose of this study was to characterize the variety and diversity of the oral mycobiome of domestic dogs and to identify the commensal and potentially pathogenic fungi present. Two hundred fifty-one buccal swabs from domestic dogs were obtained and struck onto a chromogenic fungal growth medium that distinguishes between fungal species based on colony color and morphology. After isolating and harvesting single colonies, genomic DNA was extracted from pure cultures. PCR was used to amplify a fungal-specific variable rDNA region of the genome, which was then sent for sequencing. Sequencing results were input into the NCBI BLAST database to identify individual components of the oral mycobiome of tested dogs. Of the 251 dogs swabbed, 73 had cultivable fungi present and 10 dogs had multiple fungal species isolated. Although the dogs did not show signs of oral infections at the time, we did find fungal species that cause pathogenicity in animals and humans. Among fungal isolates, Malassezia pachydermatis and species from the genus Candida were predominant. Following fungal isolate identification, antifungal drug susceptibility tests were performed on each isolate toward the medically important antifungal drugs including fluconazole, ketoconazole, and terbinafine. Drug susceptibility test results indicated that a large number of isolates had high MIC values for all three drugs. Exploring the oral mycobiome of dogs, as well as the corresponding drug susceptibility profiles, can have important implications for canine dental hygiene, health, and medical treatment. Identifying the microorganisms within the canine mouth can illustrate a common pathway for fungal pathogens of One Health concern to spread from our canine companions to humans.

Oral fluconazole has variable pharmacokinetics in dogs

The purpose of this study was to assess the effects of food and manufacturer on the oral bioavailability of fluconazole in dogs. We hypothesized feeding would decrease fluconazole bioavailability and large variability between manufacturers would occur. Six healthy purpose-bred dogs aged 2-3 years, weighing 9.5-13.7 kg, were enrolled. Each dog was administered a 100 mg fluconazole tablet from three FDA approved manufacturers (1-Glenmark, 2-Citron, 3-Harris) in a randomized crossover block study, fasted for 12 h (fasted) or 15 min after feeding (fed); each dog had 6 treatments. Blood was collected for 72 h after dosing with a 10-day washout between treatments. Fluconazole plasma concentrations were determined with mass spectrometry. Overall variability in dose-normalized drug exposure (AUC/dose) was large (range 1.9-2.9x) within each treatment, while the overall range across all treatments was 3.3-fold. The inter-dog variability in the terminal half-life was also large, 3.1-fold. The mean fed relative oral bioavailability was lower (82%-90%) compared to fasted for each formulation. Due to the large variability, the formulations were not bioequivalent. These data suggest the variability in the half-life was a major contributor to the large variability in fluconazole pharmacokinetics in dogs, while the feeding status and manufacturer were minor contributors.

Dosing protocols to increase the efficacy of butorphanol in dogs

The purpose of this study was to improve butorphanol dosing in dogs. Twelve Beagles (6 males, 6 females) were enrolled. Six were randomly allocated to each butorphanol treatment: IV (0.4 mg/kg), IV loading dose (0.2 mg/kg) with IV CRI (0.2 mg/kg/h for 8 h), SC (0.4 mg/kg), SC (0.8 mg/kg) with an equal volume sodium bicarbonate (SC-bicarbonate), and IV after CYP inhibitors. We hypothesized that the CRI would produce longer durations than IV bolus, and SC-bicarbonate suspension would produce longer durations than SC. Hypothermia, an opioid effect paralleling antinociception in dogs, and sedation were evaluated. Pharmacokinetics and CYP inhibitor effects on butorphanol pharmacokinetics were determined. Rectal temperatures were significantly lower than baseline from 1.5-4 h (IV), 1-5 h (CRI), and 2-7 h (SC-bicarbonate), but not after SC. Dogs in all treatments had sedation. Butorphanol's half-life was ~1.5 h. SC-bicarbonate had lower bioavailability (61%) relative to SC, with no sustained release, and the CRI mean steady-state plasma concentration was 43.1 ng/ml. CYP inhibitors had minor pharmacokinetic effects on butorphanol. Butorphanol 0.4 mg/kg IV and 0.2 mg/kg loading dose with 0.2 mg/kg/h CRI decreased rectal temperature, but 0.4 mg/kg SC did not. Further studies are required to determine clinical analgesia of butorphanol.

Multiple-dose pharmacokinetics and opioid effects of a novel analgesic with a deterrent to human opioid abuse (methadone-fluconazole-naltrexone) after oral administration in dogs

OBJECTIVE

To assess the pharmacokinetics and opioid effects of methadone after administration of multiple doses by means of 2 dosing regimens of methadone-fluconazole-naltrexone.

ANIMALS

12 healthy Beagles.

PROCEDURES

Dogs were randomly allocated (6 dogs/group) to receive 1 of 2 oral dosing regimens of methadone-fluconazole-naltrexone. Treatment 1 doses were administered at 0 (methadone-to-fluconazole-to-naltrexone ratio of 1:5:0.25 mg/kg), 14 (1:5:0.25), 24 (0.5:2.5:0.125), and 38 (0.5:2.5:0.125) hours. Treatment 2 doses were administered at 0 (1:5:0.25), 4 (0.5:2.5:0.125), 10 (0.5:2.5:0.125), and 24 (0.5:2.5:0.125) hours. Blood samples, rectal temperatures, and von Frey antinociceptive measurements were obtained at designated times.

RESULTS

Compared with baseline, temperatures significantly decreased for treatment 1 group dogs at 2 to ≥ 4 hours and from 16 to ≥ 50 hours (12 hours after last dose) and for treatment 2 group dogs at 2 to ≥ 36 hours (12 hours after last dose), when trough methadone concentrations were ≥ 21.3 ng/mL. Antinociception occurred after the first dose but was not maintained throughout the study. Lesions were noted in some dogs at the application site of the von Frey device. Naltrexone and β-naltrexol were sporadically detected in plasma, and naltrexone glucuronide was consistently detected.

CONCLUSIONS AND CLINICAL RELEVANCE

Opioid effects were noted after oral administration of the first dose, and data suggested that administering a second dose 6 hours later and every 12 hours thereafter was necessary to maintain opioid effects. Antinociception may have been lost because dogs became averse or hyperalgesic to the von Frey device, such that the antinociception model used here may not be robust for repeated measurements in dogs.

Perioperative analgesia associated with oral administration of a novel methadone-fluconazole-naltrexone formulation in dogs undergoing routine ovariohysterectomy

OBJECTIVE

To determine perioperative analgesia associated with oral administration of a novel methadone-fluconazole-naltrexone formulation in dogs undergoing routine ovariohysterectomy.

ANIMALS

43 healthy female dogs.

PROCEDURES

Dogs were randomly assigned to receive the methadone-fluconazole-naltrexone formulation at 1 of 2 dosages (0.5 mg/kg, 2.5 mg/kg, and 0.125 mg/kg, respectively, or 1.0 mg/kg, 5.0 mg/kg, and 0.25 mg/kg, respectively, PO, q 12 h, starting the evening before surgery; n = 15 each) or methadone alone (0.5 mg/kg, SC, q 4 h starting the morning of surgery; 13). Dogs were sedated with acepromazine, and anesthesia was induced with propofol and maintained with isoflurane. A standard ovariohysterectomy was performed by experienced surgeons. Sedation and pain severity (determined with the Glasgow Composite Pain Scale-short form [GCPS-SF]) were scored for 48 hours after surgery. Rescue analgesia was to be provided if the GCPS-SF score was > 6. Dogs also received carprofen starting the day after surgery.

RESULTS

None of the dogs required rescue analgesia. The highest recorded GCPS-SF score was 4. A significant difference in GCPS-SF score among groups was identified at 6:30 am the day after surgery, but not at any other time. The most common adverse effect was perioperative vomiting, which occurred in 11 of the 43 dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Oral administration of a methadone-fluconazole-naltrexone formulation at either of 2 dosages every 12 hours (3 total doses) was as effective as SC administration of methadone alone every 4 hours (4 total doses) in dogs undergoing routine ovariohysterectomy. Incorporation of naltrexone in the novel formulation may provide a deterrent to human opioid abuse or misuse.

Pharmacokinetics and pharmacodynamics of a novel analgesic with a deterrent to human opioid abuse (methadone-fluconazole-naltrexone) after oral administration in dogs

OBJECTIVE

To determine the effects of coadministration of naltrexone, a human opioid abuse deterrent, on the pharmacokinetics and pharmacodynamics of a methadone-fluconazole combination administered orally to dogs.

ANIMALS

12 healthy Beagles.

PROCEDURES

Dogs (body weight, 10.7 to 13.9 kg) were randomly allocated to 2 groups in a parallel design study. All dogs received fluconazole (100 mg [7.19 to 9.35 mg/kg], PO). Twelve hours later (time 0), dogs were administered methadone (10 mg [0.72 to 0.93 mg/kg]) plus fluconazole (50 mg [3.62 to 4.22 mg/kg]; methadone-fluconazole) or methadone (10 mg [0.72 to 0.93 mg/kg]) plus fluconazole (50 mg [3.60 to 4.67 mg/kg]) and naltrexone (2.5 mg [0.18 to 0.23 mg/kg]; methadone-fluconazole-naltrexone), PO, in a gelatin capsule. Blood samples were collected for pharmacokinetic analysis, and rectal temperature and sedation were assessed to evaluate opioid effects at predetermined times up to 24 hours after treatment.

RESULTS

Most dogs had slight sedation during the 12 hours after drug administration; 1 dog/group had moderate sedation at 1 time point. Mean rectal temperatures decreased significantly from baseline (immediate pretreatment) values from 2 to ≥ 12 hours and 2 to ≥ 8 hours after methadone-fluconazole and methadone-fluconazole-naltrexone treatment, respectively. Geometric mean maximum observed concentration of methadone in plasma was 35.1 and 33.5 ng/mL and geometric mean terminal half-life was 7.92 and 7.09 hours after methadone-fluconazole and methadone-fluconazole-naltrexone treatment, respectively. Naltrexone was sporadically detected in 1 dog. The active naltrexone metabolite, β-naltrexol, was not detected. The inactive metabolite, naltrexone glucuronide, was detected in all dogs administered methadone-fluconazole-naltrexone.

CONCLUSIONS AND CLINICAL RELEVANCE

Opioid effects were detected after oral administration of methadone-fluconazole or methadone-fluconazole-naltrexone. Further studies assessing additional opioid effects, including antinociception, are needed.

Clinical pharmacokinetics and outcomes of oral fluconazole therapy in dogs and cats with naturally occurring fungal disease

This multi-institutional study was designed to determine the clinical pharmacokinetics of fluconazole and outcomes in client-owned dogs (n = 37) and cats (n = 35) with fungal disease. Fluconazole serum concentrations were measured. Pharmacokinetic analysis was limited to animals at steady state (≥72 hr of treatment). The mean (range) body weight in 31 dogs was 25.6 (2.8-58.2) kg and in 31 cats was 3.9 (2.4-6.1) kg included in pharmacokinetic analyses. The dose, average steady-state serum concentrations (C_SS ), and oral clearance in dogs were 14.2 (4.5-21.3) mg/kg/d, 26.8 (3.8-61.5) µg/mL, and 0.63 ml min^-1  kg^-1 , respectively, and in cats were 18.6 (8.2-40.0) mg/kg/d, 32.1 (1.9-103.5) µg/mL, and 0.61 ml min^-1  kg^-1 , respectively. Random inter-animal pharmacokinetic variability was high in both species. Two dogs had near twofold increases in serum fluconazole when generic formulations were changed, suggesting lack of bioequivalence. Median C_SS for dogs and cats achieving clinical remission was 19.4 and 35.8 µg/ml, respectively. Starting oral doses of 10 mg/kg q12h in dogs and 50-100 mg total daily dose in cats are recommended to achieve median C_SS associated with clinical remission. Due to the large pharmacokinetic variability, individualized dose adjustments based on C_SS (therapeutic drug monitoring) and treatment failure should be considered.

Clinical and pharmacokinetic interactions between oral fluconazole and intravenous ketamine and midazolam in dogs

OBJECTIVE

To evaluate drug interactions between fluconazole and the intravenous (IV) anesthetic induction agents, ketamine and midazolam.

STUDY DESIGN

Randomized parallel study.

ANIMALS

A group of 12 adult healthy Beagle dogs.

METHODS

Dogs were randomly allocated to two groups of six dogs. Dogs in group KM were administered IV ketamine (7 mg kg^-1) and IV midazolam (0.25 mg kg^-1), and dogs in group KMF were administered fluconazole (5 mg kg^-1) orally 12 and 24 hours prior to ketamine-midazolam using the same doses as KM. Sedation scores (0-4) were assigned by investigators unaware of group assignment. Heart rate (HR) and times to sternal and standing were obtained and compared between groups for differences with p < 0.05 considered statistically significant. Blood was obtained and plasma drug concentrations were measured using liquid chromatography-mass spectrometry.

RESULTS

The times to sternal, mean 32.3 and 24.6 minutes, for groups KMF and KM, respectively, were not different between the groups. The time to standing, 73 and 36 minutes in groups KMF and KM, respectively, was significantly different (p = 0.002). The duration of elevated HR compared with baseline was longer in KMF (110 minutes) than in KM (25 minutes) (p < 0.05). In group KMF, one dog developed hyperthermia (40.6 °C), which resolved spontaneously. The clearance of ketamine and midazolam was significantly slower (approximately 50%) and the area under the curves were significantly higher (two-fold) in group KMF (p = 0.02).

CONCLUSIONS AND CLINICAL RELEVANCE

A significant interaction between oral fluconazole and IV ketamine-midazolam occurred, but the effects appear minor in healthy dogs. Based on these data, a single dose of ketamine-midazolam is not contraindicated in dogs treated with fluconazole, but the duration of effects and pharmacokinetics are altered.