Plasma and interstitial fluid antibiotic levels of subcutaneously implanted compounded florfenicol calcium sulfate beads in New Zealand White rabbits (Oryctolagus cuniculus).

OBJECTIVE: To determine antibiotic levels in plasma and interstitial fluid (ISF) after SC placement of compounded florfenicol (FF) calcium sulfate beads (CSBs) in New Zealand White rabbits (Oryctolagus cuniculus). ANIMALS: 6 juvenile female rabbits (n = 5 treatment and 1 control). METHODS: An ultrafiltration probe and CSBs were placed SC in 6 rabbits (n = 5 for FF CSBs and 1 for control CSBs). Plasma (3, 6, 12, 24, and 48 hours and 7, 14, and 21 days) and ISF (daily for 21 days) samples were collected, and FF was measured by HPLC for pharmacokinetic analysis. Hematology, biochemistry, and histopathology were assessed. RESULTS: Means ± SD for the area under the curve, maximum concentration, time of maximum concentration, terminal half-life, and mean residence time to the last data point for plasma and ISF were 16.63 ± 8.16 and 17,902 ± 7,564 h·µg/mL, 0.79 ± 0.38 and 245 ± 223 µg/mL, 2.90 ± 0.3 and 59 ± 40 hours, 30.81 ± 16.9 and 27.3 ± 9.39 hours, 23.4 ± 10 and 73.7 ± 13 hours, respectively. Plasma FF was < 2 µg/mL at all time points. The ISF FF remained > 8 µg/mL for 109.98 to 231.58 hours. One rabbit death occurred during treatment, but the cause of death was undetermined. Local tissue inflammation was present, but no clinically significant systemic adverse effects were found on hematology, biochemistry, or histopathology in the remaining rabbits. CLINICAL RELEVANCE: Florfenicol CSBs maintained antibiotic concentrations in ISF at levels likely to be effective against bacteria sensitive to > 8 µg/mL for 5 to 10 days while maintaining low (< 2 µg/mL) plasma levels. Florfenicol CSBs may be effective for local antibiotic treatment in rabbit abscesses.

Pharmacokinetics of mebendazole in plasma and cerebrospinal fluid following a single oral dose in healthy dogs.

Novel therapies are needed for treatment of gliomas. Mebendazole previously demonstrated anti-neoplastic effects on canine glioma cell lines at in vitro mean inhibitory concentrations (IC50) of 10 ng/mL. Our study aimed to titrate the oral dose of mebendazole necessary to achieve concentrations ≥10 ng/mL in cerebrospinal fluid (CSF) of healthy dogs. We hypothesized that an oral dose up to 200 mg/kg would be necessary. Phase one was a dose titration study using a total of 6 mixed breed dogs that described dose vs. plasma concentrations for 72 h after single oral dosing of either 50 mg/kg (n = 2), 100 mg/kg (n = 2), or 200 mg/kg (n = 2). Based on phase one, phase two dogs (total of 9) received 100 mg/kg (n = 4) or 200 mg/kg (n = 5) orally and blood samples were collected intermittently for 60 h with CSF samples collected intermittently for 24 h. Mebendazole was quantitated in plasma and CSF using high performance liquid chromatography. Median peak plasma concentrations (Cmax) were reached at 7 ± 2 h (100 mg/kg) of 220 ng/mL (81, 283) and at 15 ± 4 h (200 mg/kg) of 147 ng/ml (112, 298). The respective area under the curve (AUC: ng/ml/h) reported as a median was 2,119 (1,876, 3,288) vs. 3,115 (1,559, 4,972). Median plasma concentrations (ng/ml) for 100 vs. 200 mg/kg were 47 (32, 52) vs. 65 (35, 104), respectively. For CSF, the median value for Cmax (at 100 mg/kg vs. 200 mg/kg) was 8 (2, 28) vs. 21 (12, 27) and AUC was 87 (22, 157) vs. 345 (92, 372), respectively. Relative bioavailability in CSF vs. plasma was 4 to 10%. Although several animals demonstrated clinical signs indicative of gastrointestinal upset [i.e., vomiting (n = 2), diarrhea (n = 2), or both (n = 1)], these events were not considered serious. The in vitro IC50 for gliomas can be reached in CSF at 100 mg/kg (n = 1), however a 200 mg/kg dose yielded more consistent concentrations.

Disposition of a single oral dose of a cannabidiol medication in healthy cats.

The historical use of the marijuana plant for medicinal purposes is long. One of the historical uses has been for the treatment of epilepsy. Recently, the Food and Drug Administration has approved a highly purified cannabidiol medication for the add on therapy in people with certain forms of epilepsy. With the increase interest of the use of cannabidiol in the veterinary community, the aim of this study was to describe the disposition of a single dose of a cannabidiol medication in healthy cats in both the fed and fasted state. Pharmacokinetic analysis reveals that relative bioavailability of cannabidiol shows a near eleven-fold increase when administered in the fed state compared to the fasted state. Additionally, concentrations achieved at a dose of 5 mg/kg, may be sufficient to explore the therapeutic potential in cats with epilepsy.

Administration of Altrenogest to Maintain Pregnancy in Asian Elephants (Elephas maximus).

Progesterone and progesterone derivatives are key hormones in pregnancy maintenance in mammalian species. Cessation of pregnancy, including birth or miscarriage, is certain if levels of these hormones drop below a given species-specific requirement necessary to maintain pregnancy. The synthetic progestin, altrenogest, is FDA-approved in the United States for suppression of estrus or synchronization and is administered extra-label to multiple species to maintain pregnancies in cases of luteal deficiency or otherwise abnormally low progesterone levels. Three pregnant Asian elephants received altrenogest from 41 to 131 days during the final trimester of pregnancy, with parturition occurring from 15 to 31 days after altrenogest administration stopped. A single dose of 0.2 mg/kg altrenogest administered to two nonpregnant Asian elephants provided pilot pharmacokinetic data. Serum samples from two of the three clinical cases and the two pilot study elephants were analyzed using Ultra Performance Liquid chromatography coupled to a triple quadruple mass spectrometer (UPLC-MS). Small sample numbers limited analysis; however, the following were determined: AUC∞ of 635.4 ± 73.8 ng*h/mL, Cmax of 30.2 ± 14.4 ng/mL at a Tmax of 4 ± 2.8 h, terminal T1/2 of 47.5 ± 3.0 h, MRT of 36.0 + 3.4 h and Vd/F of 1243.8 + 275.0 L/kg. These data and the three described cases serve as an indication that altrenogest can be administered to Asian elephants as an exogenous progestin to support pregnancy in elephant pregnancies with low endogenous progestin levels.

Effects of a single dose of orally and rectally administered misoprostol in an in vivo endotoxemia model in healthy adult horses.

OBJECTIVE: To describe misoprostol pharmacokinetics and anti-inflammatory efficacy when administered orally or per rectum in endotoxin-challenged horses. ANIMALS: 6 healthy geldings. PROCEDURES: A randomized 3-treatment crossover design was performed with a minimum washout period of 28 days between treatment arms. Prior to endotoxin challenge (lipopolysaccharide, 30 ng/kg IV over 30 minutes), horses received misoprostol (5 µg/kg once) per os (M-PO) or per rectum (M-PR) or water as control (CON). Clinical parameters were evaluated and blood samples obtained to measure plasma misoprostol free acid concentration, leukocyte counts, and tumor necrosis factor-α (TNFα) and interleukin 6 (IL-6) leukocyte gene expression and serum concentrations. RESULTS: In the M-PO treatment arm, maximum plasma concentration and area under the concentration-versus-time curve (mean ± SD) were higher (5,209 ± 3,487 pg/mL and 17,998,254 ± 13,194,420 h·pg/mL, respectively) and median (interquartile range) time to maximum concentration (25 min [18 to 34 min]) was longer than in the M-PR treatment arm (854 ± 855 pg/mL; 644,960 ± 558,866 h·pg/mL; 3 min [3 to 3.5 min]). Significant differences in clinical parameters, leukocyte counts, and TNFα or IL-6 gene expression or serum protein concentration were not detected. Downregulation of relative gene expression was appreciated for individual horses in the M-PO and M-PR treatment arms at select time points. CLINICAL RELEVANCE: Considerable variability in measured parameters was detected among horses within and between treatment arms. Misoprostol absorption and systemic exposure after PO administration differed from previous reports in horses not administered LPS. Investigation of multidose administration of misoprostol is warranted to better evaluate efficacy as an anti-inflammatory therapeutic.

Pharmacokinetics of Pimobendan and Its Metabolite O-Desmethyl-Pimobendan Following Rectal Administration to Healthy Dogs.

Objective: This study describes the pharmacokinetics of parent pimobendan (PIM) and its active metabolite, o-desmethyl-pimobendan (ODMP), after oral and rectal administration of pimobendan to healthy dogs. Animals: A total of eight healthy privately owned dogs were used in this study. Procedures: The dogs received a single dose (0.5 mg/kg) of a commercially available pimobendan tablet per os (PO). Twelve blood samples were collected over a 12-h period for pharmacokinetic analysis. After a 24-h washout period, the dogs received the same dose of pimobendan solution per rectum (PR), and samples were obtained at the same time for analysis. Results: For PIM, PO vs. PR, respectively, the mean maximum plasma concentration (C max, ng/ml) was 49.1 ± 28.7 vs. 10.1 ± 2, the time to reach a maximum concentration (T max, h) was 2.1 ± 0.9 vs. 1 ± 0.4, the disappearance half-life (t 1/2, h) was 1.8 ± 0.8 vs. 2.2 ± 0.6, and the area under the concentration-time curve (AUC, ng*h/ml) was 148.4 ± 71.6 vs. 31.1 ± 11.9, with relative bioavailability (F, %) of 25 ± 8. For ODMP, PO vs. PR, respectively, C max was 30.9 ± 10.4 vs. 8.8 ± 4.8, T max was 3.2 ± 1.6 vs. 1.7 ± 1.1, and t 1/2 was 5.0 ± 2.7 vs. 8.3 ± 4.8, with AUC of 167.8 ± 36.2 vs. 50.1 ± 19.2 and F of 28 ± 6. The differences between PO and PR were significant (P < 0.03) for AUC and C max for both PIM and ODMP. Conclusions and Clinical Relevance: The pharmacokinetics of PIM and ODMP were described following PO and PR administration. The findings suggest that pimobendan PR might achieve effective concentrations and, as such, warrant future studies of clinical effectiveness in treating dogs with congestive heart failure and which are unable to receive medication PO.

Regulation of the neuroendocrine axis in male rats by soy-based diets is independent of age and due specifically to isoflavone action†.

Soy-based foods are consumed for their health beneficial effects, implying that the population is exposed to soy isoflavones in the diet. Herein, male rats at 21, 35, and 75 days of age were maintained either on a casein control diet, soybean meal (SBM), or control diet supplemented with daidzin and genistin (G + D) for 14 days. Feeding of SBM and G + D diets decreased testicular testosterone (T) secretion regardless of age. Altered androgen secretion was due to decreased (P < 0.05) Star and Hsd17ß protein in the testes and was associated with increased (P < 0.05) Lhß and Fshß subunit protein expression in pituitary glands. Second, male rats were fed either a casein control diet, control diet + daidzin, control diet + genistin, or control diet + genistin + daidzin (G + D). Compared to control, feeding of all isoflavone-containing diets decreased (P < 0.05) testicular T concentrations, and more so in the G + D diet group. Interestingly, Esr1 and androgen receptor protein and pituitary Fshß with Lhß subunit protein were increased (P < 0.05) by feeding of genistin and G + D diets, but not the daidzin diet. However, daidzein and genistein both caused a concentration dependent inhibition (P < 0.05) of T secretion by Leydig cells in vitro with IC50 of 184 ηM and 36 ηM, respectively. Results demonstrated that altered testicular steroidogenic capacity and pituitary FSHß and LHß subunit expression due to soy-based diets result from specific actions by genistein and daidzein. Experiments to assess effects of isoflavone regulation of intratesticular androgen concentrations on male fertility are warranted.

Nothing Ventured, Nothing Gained: Regulations Cripple Potentially Life-Saving Research of Illicit Substances.

Modern day research, in an attempt to determine the potential therapeutic and adverse effects of illicit substances, is a growing field, but one that faces many regulatory challenges. Due to the potential abuse of illicit substances such as Cannabis, 3,4-methylenedioxymethamphetamine (MDMA), lysergic acid diethylamide (LSD) and psilocybin, regulations have been conceived with the intent of preventing harm and addiction. However, these regulations have also become a major barrier for the scientific community as they suffocate attempts of the scientists to acquire illicit substances for research purposes. Therefore, it is imperative to modify the current regulations of drug scheduling, leading to a reclassification of illicit substances that would allow for extensive testing in research settings. This reclassification effort could advance the potentially life-saving research of illicit substances.

Pharmacokinetic Profiles of Gabapentin after Oral and Subcutaneous Administration in Black-tailed Prairie Dogs (Cynomys ludovicianus).

In veterinary and human medicine, gabapentin (a chemical analog of γ-aminobutyric acid) is commonly prescribed to treat postoperative and chronic neuropathic pain. This study explored the pharmacokinetics of oral and subcutaneous administration of gabapentin at high (80 mg/kg) and low (30 mg/kg) doses as a potential analgesic in black-tailed prairie dogs (Cynomys ludovicianus; n = 24). The doses (30 and 80 mg/kg) and half maximal effective concentration (1.4 to 16.7 ng/mL) for this study were extrapolated from pharmacokinetic efficacy studies in rats, rabbits, and cats. Gabapentin in plasma was measured by using an immunoassay, and data were evaluated using noncompartmental analysis. The peak plasma concentrations (mean ±1 SD) were 42.6 ±14.8 and 115.5 ±15.2 ng/mL, respectively, after 30 and 80 mg/kg SC and 14.5 ±3.5 and 20.7 ±6.1 ng/mL after the low and high oral dosages, respectively. All peak plasma concentrations of gabapentin occurred within 5 h of administration. Disappearance half-lives for the low and high oral doses were 7.4 ± 6.0 h and 5.0 ± 0.8 h, respectively. The results of this study demonstrate that oral administration of gabapentin at low (30 mg/kg) doses likely would achieve and maintain plasma concentrations at half maximum effective concentration for 12 h, making it a viable option for an every 12-h treatment.

Effects of oral administration of 5 immunosuppressive agents on activated T-cell cytokine expression in healthy dogs.

BACKGROUND: Dogs are often adminstered >1 immunosuppressive medication when treating immune-mediated diseases, and determining whether these different medications affect IL-2 expression would be useful when performing pharmacodynamic monitoring during cyclosporine therapy. HYPOTHESIS/OBJECTIVES: To determine the effects of 5 medications (prednisone, cyclosporine, azathioprine, mycophenolate mofetil, and leflunomide) on activated T-cell expression of the cytokines IL-2 and interferon-gamma (IFN-γ). ANIMALS: Eight healthy dogs. METHODS: Randomized, cross-over study comparing values before and after treatment, and comparing values after treatment among drugs. Dogs were administered each drug at standard oral doses for 1 week, with a washout of at least 21 days. Activated T-cell expression of IL-2 and IFN-γ mRNA was measured by quantitative reverse transcription polymerase chain reaction. Blood drug concentrations were measured for cyclosporine, mycophenolate, and leflunomide metabolites. RESULTS: Least squares means (with 95% confidence interval) before treatment for IL-2 (2.91 [2.32-3.50] ΔCt) and IFN-γ (2.33 [1.66-3.00 ΔCt]) values were significantly lower (both P < .001) than values after treatment (10.75 [10.16-11.34] and 10.79 [10.11-11.46] ΔCt, respectively) with cyclosporine. Similarly, least squares means before treatment for IL-2 (1.55 [1.07-2.02] ΔCt) and IFN-γ (2.62 [2.32-2.92] ΔCt) values were significantly lower (both P < .001) than values after treatment (3.55 [3.06-4.00] and 5.22 [4.92-5.52] ΔCt, respectively) with prednisone. Comparing delta cycle threshold values after treatment among drugs, cyclosporine was significantly different than prednisone (IL-2 and IFN-γ both P < .001), with cyclosporine more suppressive than prednisone. CONCLUSIONS AND CLINICAL IMPORTANCE: Prednisone and cyclosporine both affected expression of IL-2 and IFN-γ, suggesting that both have the ability to influence results when utilizing pharmacodynamic monitoring of cyclosporine treatment.

Adverse pharmacokinetic interactions between illicit substances and clinical drugs.

Adverse pharmacokinetic interactions between illicit substances and clinical drugs are of a significant health concern. Illicit substances are taken by healthy individuals as well as by patients with medical conditions such as mental illnesses, acquired immunodeficiency syndrome, diabetes mellitus and cancer. Many individuals that use illicit substances simultaneously take clinical drugs meant for targeted treatment. This concomitant usage can lead to life-threatening pharmacokinetic interactions between illicit substances and clinical drugs. Optimal levels and activity of drug-metabolizing enzymes and drug-transporters are crucial for metabolism and disposition of illicit substances as well as clinical drugs. However, both illicit substances and clinical drugs can induce changes in the expression and/or activity of drug-metabolizing enzymes and drug-transporters. Consequently, with concomitant usage, illicit substances can adversely influence the therapeutic outcome of coadministered clinical drugs. Likewise, clinical drugs can adversely affect the response of coadministered illicit substances. While the interactions between illicit substances and clinical drugs pose a tremendous health and financial burden, they lack a similar level of attention as drug-drug, food-drug, supplement-drug, herb-drug, disease-drug, or other substance-drug interactions such as alcohol-drug and tobacco-drug interactions. This review highlights the clinical pharmacokinetic interactions between clinical drugs and commonly used illicit substances such as cannabis, cocaine and 3, 4-Methylenedioxymethamphetamine (MDMA). Rigorous efforts are warranted to further understand the underlying mechanisms responsible for these clinical pharmacokinetic interactions. It is also critical to extend the awareness of the life-threatening adverse interactions to both health care professionals and patients.

Analysis of the effects of storage temperature and contamination on aerobic bacterial culture results of bronchoalveolar lavage fluid.

BACKGROUND: Storage temperature of bronchoalveolar lavage fluid (BALF) impacts cytological evaluation. The effect of storage temperature before bacterial culture has not been evaluated. OBJECTIVES: To assess whether BALF storage temperature alters aerobic bacterial culture results. ANIMALS: Eight healthy, male, intact, purpose-bred Beagles. METHODS: Prospective, controlled investigation. Samples of BALF were collected sterilely. Half of each sample was reserved for controls, and half was inoculated with 104 colony forming units per milliliter (cfu/mL) Bordetella bronchiseptica and 102 cfu/mL Escherichia coli. Control and inoculated samples each were separated into 4 aliquots (1 plated immediately; 3 stored at 4, 24, or 37°C, respectively, for 24 hours before aerobic bacterial culture). Colony counts were compared across treatments for each organism. RESULTS: In inoculated samples, a statistical difference could not be detected in growth of E. coli or B. bronchiseptica between the baseline culture and BALF stored at 4°C for 24 hours before culture. However, for E. coli, growth in cfu/mL at both 24 and 37°C was higher compared to baseline (P < .05) and compared to 4°C (P < .05). For B. bronchiseptica cfu/mL, growth at 37°C was significantly different (P = .003) compared to both baseline and 4°C. CONCLUSIONS AND CLINICAL IMPORTANCE: Samples of BALF may be stored at 4°C for 24 hours before culture without substantially altering culture results. Inappropriate storage or shipment temperature (room temperature or exposure to heat) can result in overgrowth of E. coli or B. bronchiseptica, which could alter clinical decisions.

Pharmacokinetics of a commercially available product and a compounded formulation of extended-release levetiracetam after oral administration of a single dose in cats.

OBJECTIVE: To compare pharmacokinetics of levetiracetam in serum and CSF of cats after oral administration of extended-release (ER) levetiracetam. ANIMALS: 9 healthy cats. PROCEDURES: Cats received 1 dose of a commercially available ER levetiracetam product (500 mg, PO). Thirteen blood and 10 CSF samples were collected over a 24-hour period for pharmacokinetic analysis. After 1 week, cats received 1 dose of a compounded ER levetiracetam formulation (500 mg, PO), and samples were obtained at the same times for analysis. RESULTS: CSF concentrations of levetiracetam closely paralleled serum concentrations. There were significant differences between the commercially available product and the compounded formulation for mean ± SD serum maximum concentration (Cmax; 126 ± 33 µg/mL and 169 ± 51 µg/mL, respectively), Cmax corrected for dose (0.83 ± 0.10 µg/mL/mg and 1.10 ± 0.28 µg/mL/mg, respectively), and time to Cmax (5.1 ± 1.6 hours and 3.1 ± 1.5 hours, respectively). Half-life for the commercially available product and compounded formulation of ER levetiracetam was 4.3 ± 2.0 hours and 5.0 ± 1.6 hours, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The commercially available product and compounded formulation of ER levetiracetam both maintained concentrations in healthy cats 12 hours after oral administration that have been found to be therapeutic in humans (ie, 5 µg/mL). Results of this study supported dosing intervals of 12 hours, and potentially 24 hours, for oral administration of ER levetiracetam to cats. Monitoring of serum concentrations of levetiracetam can be used as an accurate representation of levetiracetam concentrations in CSF of cats.

Pharmacokinetics and safety of zonisamide after oral administration of single and multiple doses to Hispaniolan Amazon parrots (Amazona ventralis).

OBJECTIVE To determine pharmacokinetics after oral administration of single and multiple doses and to assess the safety of zonisamide in Hispaniolan Amazon parrots (Amazona ventralis). ANIMALS 12 adult Hispaniolan Amazon parrots. PROCEDURES Zonisamide (30 mg/kg, PO) was administered once to 6 parrots in a single-dose trial. Six months later, a multiple-dose trial was performed in which 8 parrots received zonisamide (20 mg/kg, PO, q 12 h for 10 days) and 4 parrots served as control birds. Safety was assessed through monitoring of body weight, attitude, and urofeces and comparison of those variables and results of CBC and biochemical analyses between control and treatment groups. RESULTS Mean ± SD maximum plasma concentration of zonisamide for the single- and multiple-dose trials was 21.19 ± 3.42 µg/mL at 4.75 hours and 25.11 ± 1.81 µg/mL at 2.25 hours after administration, respectively. Mean plasma elimination half-life for the single- and multiple-dose trials was 13.34 ± 2.10 hours and 9.76 ± 0.93 hours, respectively. Pharmacokinetic values supported accumulation in the multiple-dose trial. There were no significant differences in body weight, appearance of urofeces, or appetite between treated and control birds. Although treated birds had several significant differences in hematologic and biochemical variables, all variables remained within reference values for this species. CONCLUSIONS AND CLINICAL RELEVANCE Twice-daily oral administration of zonisamide to Hispaniolan Amazon parrots resulted in plasma concentrations known to be therapeutic in dogs without evidence of adverse effects on body weight, attitude, and urofeces or clinically relevant changes to hematologic and biochemical variables.

Comparison of predicted intrinsic hepatic clearance of 30 pharmaceuticals in canine and feline liver microsomes.

1. Known cytochrome P450 (CYP) substrates in humans are used in veterinary medicine, with limited knowledge of the similarity or variation in CYP metabolism. Comparison of canine and feline CYP metabolism via liver microsomes report that human CYP probes and inhibitors demonstrate differing rates of intrinsic clearance (CLint). 2. The purpose of this study was to utilize a high-throughput liver microsome substrate depletion assay, combined with microsomal and plasma protein binding to compare the predicted hepatic clearance (CLhep) of thirty therapeutic agents used off-label in canines and felines, using both the well-stirred and parallel tube models. 3. In canine liver microsomes, 3/30 substrates did not have quantifiable CLint, while midazolam and amitriptyline CLint was too rapid for accurate determination. A CLhep was calculated for 29/30 substrates in feline microsomes. Overall, canine CLhep was faster compared to the feline, with fold differences ranging from 2-20-fold. 4. A comparison between the well-stirred and parallel tube model indicates that the parallel tube model reports a slighter higher CLhep in both species. 5. The differences in CYP metabolism between canine and feline highlight the need for additional research into CYP expression and specificity.

Serum theophylline after multiple dosing with transdermal gels in cats.

OBJECTIVES: Our objectives were, first, to determine if therapeutic serum theophylline concentrations could be achieved using long-term, once-daily dosing of transdermal theophylline and, secondarily, to evaluate the difference between two transdermal theophylline formulations. METHODS: Seven healthy cats, 1-10 years of age, were evaluated in a two-way, randomized, double-blinded, crossover study. Participants received transdermal theophylline at 15 mg/kg for 21 days in either pluronic lecithin organogel (PLO) or Lipoderm formulation. On day 22, blood was collected 2, 6, 14 and 24 h after dosing. After a 14 day washout period, blood was collected to verify non-detectible theophylline concentrations. The alternate formulation was administered for 21 days, and sampling was repeated. Serum theophylline concentrations were determined using an automated immunoassay. Serum concentrations were compared between formulations using a two-way random-measures ANOVA and over time within a formulation using a repeated-measures ANOVA. RESULTS: Therapeutic serum theophylline concentrations were achieved for 2/7 cats in each group. Of 56 serum theophylline measurements obtained, only seven (13%) were within the therapeutic range. No significant difference was detected in drug concentrations achieved by the transdermal formulations at any time point. In addition, no significant difference in serum theophylline concentrations was noted between time points for PLO ( P = 0.751) or Lipoderm ( P = 0.107). CONCLUSIONS AND RELEVANCE: Once-daily transdermal dosing of theophylline does not reliably achieve therapeutic concentrations. Individual cats may achieve therapeutic concentrations. No significant difference was noted between PLO and Lipoderm formulations. Therefore, transdermal theophylline formulations should not be considered as a first-line therapy in feline asthma patients.

Identification and quantification of domestic feline cytochrome P450 transcriptome across multiple tissues.

Understanding of cytochrome P450 (CYP) isoform distribution and function in the domestic feline is limited. Only a few studies have defined individual CYP isoforms across metabolically relevant tissues, hampering the ability to predict drug metabolism and potential drug-drug interactions. Using RNA sequencing (RNA-seq), transcriptomes from the 99 Lives Cat Genome Sequencing Initiative databank combined with experimentally acquired whole transcriptome sequencing of healthy, adult male (n = 2) and female (n = 2) domestic felines, expression of 42 CYP isoforms were identified in 20 different tissues. Thirty-seven of these isoforms had not been previously reported in cats. Depending on the tissue, three to twenty-nine CYP isoform transcripts were expressed. The feline genome annotations did not differentiate CYP2E1 and 2E2 genes, demonstrating poor annotation for this gene using the reference genome. As the majority of the sequences are based on automated pipelines, complete cDNA sequences for translation into CYP protein sequences could not be determined. This study is the first to identify and characterize 37 additional CYP isoforms in feline tissues, increasing the number of identified CYP from the previously reported seven isoforms to 42 across 20 tissues.

Patterns of Fluoroquinolone Resistance in Enterobacteriaceae Isolated from the Assiut University Hospitals, Egypt: A Comparative Study.

Background: An increasing pattern of fluoroquinolone resistance (FQR) among bacterial pathogens has been described worldwide. In this study, we compared the patterns of genetic mechanisms that confer FQR for Escherichia coli and Klebsiella pneumoniae isolated from the Assiut University Hospitals in Egypt. Methods: Eighty-seven clinical E. coli and K. pneumoniae isolates were tested for mutations in gyrA, gyrB, parC, and parE genes by polymerase chain reaction (PCR) amplification and DNA sequencing. The presence of plasmid-mediated quinolone resistance (PMQR) genes qnrA, qnrB, qnrS, aac(6')-Ib, qepA was screened by PCR and characterized by conjugation. Correlations between different FQR mechanisms and ciprofloxacin minimal inhibitory concentration (MIC) levels were determined. Results: A higher number of quinolone resistance-determining region (QRDR) mutations was detected in E. coli, while the number of PMQR determinants was significantly higher in K. pneumoniae. However, K. pneumoniae showed stronger correlations than E. coli between MIC levels and number of mutations in the QRDR per isolate (rs = 0.8, p < 0.0001 and rs = 0.7, p < 0.0001, respectively) as well as between MIC levels and number of plasmids (rs = 0.4, p = 0.005 and rs = 0.3, p = 0.02, respectively). Conclusions: Although we observed a prevalence of chromosomal mutations for E. coli and the presence of plasmid-encoded genes for K. pneumoniae that resulted in FQR phenotype, high levels of FQR appeared to occur as a result of gradual accumulation of mutations in QRDR for both bacteria. To our best of knowledge, this is the first study to report and compare the correlation between FQ MIC levels and different genetic mechanisms for FQR in Enterobacteriaceae.

Pharmacokinetics and pharmacodynamics of oral pradofloxacin administration in dogs.

OBJECTIVE To determine whether target values for pharmacokinetic-pharmacodynamic (PK-PD) indices against selected canine pathogens were achievable for pradofloxacin in various canine fluids and leukocytes. ANIMALS 8 healthy adult hounds (experiments 1 and 2) and 6 healthy adult dogs (experiment 3). PROCEDURES In 3 experiments, pradofloxacin (3, 6, or 12 mg/kg) and enrofloxacin (5 or 10 mg/kg) were orally administered once a day for 5 days, and blood, interstitial fluid (ISF), and other fluid samples were collected at various points. Sample drug concentrations were measured, and noncompartmental pharmacokinetic analysis was performed; then, PK-PD indices (ratios between maximum observed concentration [Cmax] and minimum inhibitory or mutant prevention concentrations) were determined for 7 bacterial species. RESULTS PK-PD values for pradofloxacin at 3 mg/kg were approximately 5 times as high in leukocyte versus plasma and were lowest in CSF, synovial fluid, and aqueous humor. No significant differences were noted between serum and ISF. Value ratios for serum versus other body fluids were numerically higher for pradofloxacin (vs enrofloxacin) for all fluid types except CSF and aqueous humor. Target PK-PD values were exceeded for pradofloxacin against all 7 bacterial species in leukocytes and against all species except Bacteroides spp in serum and ISF. Enrofloxacin achieved the target Cmax-to-minimum inhibitory concentration ratio against Pasteurella multocida in serum, ISF, and leukocytes and for Staphylococcus pseudintermedius in serum and leukocytes. A Cmax-to-mutant prevention concentration ratio ≥ 1 against Eschericha coli was achieved for pradofloxacin at 6 mg/kg. CONCLUSIONS AND CLINICAL RELEVANCE These findings supported once-daily oral administration of pradofloxacin to dogs at the currently recommended dose (7.5 mg/kg).

Pharmacokinetics of Single-Dose Oral Pregabalin Administration in Normal Cats.

Objective: To describe the pharmacokinetic parameters of oral pregabalin in normal cats after single oral dosing. Animals: Six healthy adult research cats. Procedures: Following sedation and indwelling catheter placement, one oral (4 mg/kg) dose of pregabalin was administered. Blood samples were collected at 0, 15 and 30 min and 1, 1.5, 2, 3, 4, 6, 8, 12, 24, and 36 h after administration. Plasma pregabalin concentrations were measured by high-performance liquid chromatography and subjected to pharmacokinetic analysis using commercial software. Results: Four of six cats developed moderate sedation after pregabalin administration. The peak pregabalin concentration was 8.3 ± 1.6 µg/ml which occurred at 2.9 ± 1.2 h. Elimination half-life was 10.4 ± 2.6 h and area under the curve was 133.9 ± 71.5 µg-h/ml. Time above the minimum therapeutic concentration for seizure control in dogs and people (2.8 µg/ml) was 17.6 ± 6.2 h. Using these data, predicted minimum, maximum and average steady state concentrations were calculated for 12 and 24 h dosing intervals. Conclusions and Clinical Relevance: Pregabalin (4 mg/kg) administered orally to cats results in plasma concentrations within the range considered to be efficacious for seizure control in dogs and humans between 1.5 and at least 12 h. Because of moderate sedative side effects in the majority of cats at this dose and high calculated maximum steady state concentrations, a lower dose, given more frequently (1-2 mg/kg q 12 h), should be evaluated in prospective clinical studies.