ACVIM consensus statement on the treatment of immune thrombocytopenia in dogs and cats.

Management of immune thrombocytopenia (ITP) in dogs and cats is evolving, but there are no evidence-based guidelines to assist clinicians with treatment decisions. Likewise, the overall goals for treatment of ITP have not been established. Immunosuppressive doses of glucocorticoids are the first line treatment, but optimal treatment regimens beyond glucocorticoids remain uncertain. Additional options include secondary immunosuppressive drugs such as azathioprine, modified cyclosporine, and mycophenolate mofetil, usually selected based on clinician preference. Vincristine, human IV immunoglobulin (hIVIg), and transfusion of platelet or red blood cell-containing products are often used in more severe cases. Splenectomy and thrombopoietin receptor agonists are usually reserved for refractory cases, but when and in which patient these modalities should be employed is under debate. To develop evidence-based guidelines for individualized treatment of ITP patients, we asked 20 Population Intervention Comparison Outcome (PICO) format questions. These were addressed by 17 evidence evaluators using a literature pool of 288 articles identified by a structured search strategy. Evidence evaluators, using panel-designed templates and data extraction tools, summarized evidence and created guideline recommendations. These were integrated by treatment domain chairs and then refined by iterative Delphi survey review to reach consensus on the final guidelines. In addition, 19 non-PICO questions covering scenarios in which evidence was lacking or of low quality were answered by expert opinion using iterative Delphi surveys with panelist integration and refinement. Commentary was solicited from multiple relevant professional organizations before finalizing the consensus. The rigorous consensus process identified few comparative treatment studies, highlighting many areas of ITP treatment requiring additional studies. This statement is a companion manuscript to the ACVIM Consensus Statement on the Diagnosis of Immune Thrombocytopenia in Dogs and Cats.

Potential to use cannabinoids as adjunct therapy for dexamethasone: An in vitro study with canine peripheral blood mononuclear cells.

Dexamethasone (dex) is a potent glucocorticoid used to treat a variety of diseases. It is widely used in veterinary medicine in many species; for instance, in dogs, it can be used for emergent cases of anaphylaxis or trauma, management of immune-mediated hemolytic anemia or thrombocytopenia, certain cancers, allergic reactions, and topically for skin or eye inflammation. Dex is not without its side effects, especially when administered systemically, which might compromise compliance and effective treatment. Thus, adjunct therapies have been suggested to allow for decreased dex dosing and reduction in side effects while maintaining immunosuppressive efficacy. The goal of this study was to evaluate the potential for cannabinoids to serve as adjunct therapies for dex. Immune function was assessed in canine peripheral blood mononuclear cells (PBMCs) after treatment with dex with and without cannabidiol (CBD) and/or Δ9-tetrahydrocannabinol (THC). Dex suppressed IFN-γ protein secretion in a concentration-dependent manner and this suppression by low concentrations of dex was enhanced in the presence of CBD, THC, or the combination of CBD and THC. Similar effects were found with INFG and TNFA mRNA expression. These findings provide a rationale for using CBD or THC in vivo to reduce dex dosing and side effects.

Canine immune cells express high levels of CB1 and CB2 cannabinoid receptors and cannabinoid-mediated alteration of canine cytokine production is vehicle-dependent.

With the increased popularity and societal acceptance of marijuana and cannabidiol (CBD) use in humans, there is an interest in using cannabinoids in veterinary medicine. There have been a few placebo-controlled clinical trials in dogs suggesting that cannabis-containing extracts are beneficial for dogs with inflammatory diseases such as osteoarthritis, and there is growing interest in their immunosuppressive potential for the treatment of immune-mediated diseases. Since cannabinoids exhibit anti-inflammatory and immunosuppressive effects in many species, the purpose of these studies was to examine whether the plant-derived cannabinoids, CBD and Δ9-tetrahydrocannabinol (THC), would also suppress immune function in canine peripheral blood mononuclear cells (PBMCs). Another goal was to characterize expression of the cannabinoid receptors, CB1 and CB2, in canine immune cells. We hypothesized that CBD and THC would suppress stimulated cytokine expression and that both cannabinoid receptors would be expressed in canine immune cells. Surprisingly, cannabinoid suppressive effects in canine PMBCs were quite modest, with the most robust effect occurring at early stimulation times and predominantly by THC. We further showed that cannabinoid-mediated suppression was dog- and vehicle-dependent with CBD and THC delivered in dimethyl sulfoxide (DMSO) producing more immune suppressive effects as compared to ethanol (ETOH). PCR, flow cytometry, and immunohistochemical staining demonstrated that both CB1 and CB2 are expressed in canine immune cells. Together these data show that canine immune cells are sensitive to suppression by cannabinoids, but more detailed studies are needed to further understand the mechanisms and broad effects of these compounds in the dog.

Medical Management of Canine Chronic Ulcerative Stomatitis Using Cyclosporine and Metronidazole.

Canine chronic ulcerative stomatitis (CCUS) is a spontaneously occurring, painful, and often debilitating condition of the oral cavity, with a suspected immune-mediated component. The response to pharmacological treatment is generally poor, thus the need to identify more effective medical therapies for this condition. This article describes a prospective clinical trial that was designed to evaluate the efficiency of a combination of cyclosporine and metronidazole in managing CCUS. The hypothesis was that a combination of cyclosporine and metronidazole would effectively minimize clinical signs associated with CCUS. Ten client-owned dogs with a biopsy-confirmed diagnosis consistent with CCUS were prescribed cyclosporine (5 mg/kg) for 1 week, followed by the addition of metronidazole (15-20 mg/kg), both administered orally once daily. The cyclosporine dosage interval was lengthened over time. Dogs were observed for a 6-month period and evaluated using a 32-point Canine Ulcerative Stomatitis Disease Activity Index (CUSDAI). Regular cyclosporine therapeutic drug monitoring was also conducted by the measurement of whole blood cyclosporine levels and the pharmacodynamic assessment of the T-cell expression of IL-2. The results demonstrated that a combination of cyclosporine and metronidazole was effective in minimizing the clinical signs of CCUS and in reducing CUSDAI scores. Neither blood cyclosporine levels nor the T-cell expression of IL-2 predicted improvement in clinical signs and CUSDAI scores, although there was a correlation between blood drug concentrations and the suppression of T-cell IL-2 expression. The evaluation of clinical signs and CUSDAI scores appears to be the most effective means of assessing response to therapy, and therapeutic drug level monitoring does not appear to be routinely indicated.

Anticoagulant profile of subcutaneous enoxaparin in healthy dogs.

Our study objective was to identify a subcutaneous enoxaparin dosage that provided a consistent anticoagulant intensity in dogs. Our hypotheses were that a dose of 0.8 mg/kg would provide inconsistent anticoagulation, a higher dose would provide consistent anticoagulation over a greater duration of time, and viscoelastometry would effectively monitor the anticoagulant status. Six healthy dogs received two subcutaneous enoxaparin doses (0.8 and 2 mg/kg) for anti-Xa activity determinations and pharmacokinetic modeling. Based on calculations derived from these results, 1.3 mg/kg, SC, q8 h was administered for seven doses. Target ranges for anticoagulant intensity were defined as anti-Xa activity of 0.5-1 U/ml, and change from baseline of two viscoelastometric parameters: activated clotting time (ΔACT; ≥40 s), and clot rate (CRpost; ≤20 U/min). Following an initial injection at 1.3 mg/kg, anti-Xa activity of 5/6 dogs reached or exceeded the target range. Following the final dose, anti-Xa activity reached or exceeded the target range in all dogs, and ΔACT and CRpost values exceeded target for 2-6 and 4-12 h, respectively. At an enoxaparin dosage of 1.3 mg/kg, SC, q8 h, anti-Xa activity was consistently above the minimum threshold of the target range; however, the safety of this dosage remains to be determined.

Effects of leukoreduction on N-methylhistamine concentration in stored units of canine whole blood.

OBJECTIVE: To determine the effects of leukoreduction on N-methylhistamine (NMH; a stable histamine metabolite) concentration in units of canine whole blood during storage and incubation at room temperature (approx 22 °C) to simulate temperature conditions during transfusion. ANIMALS: 8 healthy adult Walker Hounds. PROCEDURES: A standard unit of blood (450 mL) was obtained from each dog twice, with at least 28 days between donations. Blood units collected from 4 dogs during the first donation underwent leukoreduction, whereas the blood units collected from the other 4 dogs did not undergo leukoreduction, prior to storage at 4 °C. The alternate treatment was applied to blood units collected during the second donation. A sample from each unit was obtained for determination of plasma NMH concentration the day of donation (before and after leukoreduction when applicable) and before and after incubation at room temperature for 5 hours on days 14 and 28 of storage. RESULTS: Units that underwent leukoreduction had substantially lower leukocyte and platelet counts than nonleukoreduced units. Plasma NMH concentration increased immediately after leukoreduction but did not change significantly during the subsequent 28 days of storage, nor did it differ between units that did and did not undergo leukoreduction. CONCLUSIONS AND CLINICAL RELEVANCE: Leukoreduction and simulated transfusion temperature did not affect the histamine load in units of canine whole blood during the first 28 days of storage. Further research is necessary to determine whether histamine contributes to the development and severity of blood transfusion reactions in dogs.

Effects of pentoxifylline on canine platelet aggregation.

BACKGROUND: Pentoxifylline can decrease platelet function in humans, but the anti-platelet effects of pentoxifylline in dogs is unknown. The addition of a luciferin-luciferase reagent during platelet aggregometry can induce a dose-dependent potentiation of platelet aggregation. OBJECTIVE: To determine if exposure to pentoxifylline, without the addition of a luciferin-luciferase reagent during aggregometry, causes canine platelet dysfunction. Our hypotheses were that pentoxifylline would inhibit platelet function, and that the addition of a luciferin-luciferase reagent would obscure detection of pentoxifylline-induced platelet dysfunction as measured via aggregometry. METHODS: Seven healthy Walker hound dogs. Platelet-rich plasma (PRP) and whole blood were treated for 30 minutes with pentoxifylline: 0 (control), 1 and 2 µg/mL. The platelet aggregation was determined using optical (maximum amplitude) and impedance (ohms) aggregometry using collagen as the agonists, with and without a luciferin-luciferase reagent. Four samples were analysed per concentration and the results were averaged. RESULTS: Based on optical aggregometry, there was no difference (p = 0.964) in the mean maximum amplitude at any pentoxifylline concentration, with and without the luciferin-luciferase reagent. During impedance aggregometry, the addition of a luciferin-luciferase reagent was associated with significantly (p < 0.001) greater platelet aggregation in response to a collagen agonist, regardless of the presence or absence of pentoxifylline. CONCLUSIONS: Pentoxifylline does not exert an in vitro anti-platelet effect on canine platelet aggregation when collagen is used as an agonist, but it is unknown if long-term oral drug administration will inhibit platelet aggregation. The addition of a luciferin-luciferase reagent during platelet aggregometry can artificially enhance canine platelet aggregation.

Effects of desmopressin acetate administration in healthy dogs receiving prednisolone.

BACKGROUND: Glucocorticoids are used for a variety of purposes in veterinary medicine but often are associated with clinically important adverse effects. Polyuria and polydipsia are the most frustrating adverse effects noted by owners. OBJECTIVE: To determine whether administration of desmopressin ameliorates polyuria and polydipsia associated with prednisolone administration. ANIMALS: Seven healthy adult Walker Hounds. METHODS: Prospective hypothesis testing study. Daily water intake and urine specific gravity (USG) were measured in dogs under 4 separate sequential conditions: no medications (C), prednisolone only (P), prednisolone and desmopressin (PD), and prednisolone after discontinuation of desmopressin (PAD). RESULTS: When compared to baseline, 6 of 7 dogs became polydipsic after administration of prednisolone (0.5 mg/kg PO q12h). When desmopressin (5 µg/dog SC q12h) was administered to dogs receiving prednisolone, significant decreases in water intake and serum sodium concentration occurred, and USG increased significantly. CONCLUSIONS AND CLINICAL IMPORTANCE: Administration of desmopressin to dogs receiving prednisolone significantly decreased water intake and serum sodium concentration, and increased USG. Our results suggest that, in some dogs, desmopressin ameliorates the most important adverse effect of prednisolone noted by owners, but that hyponatremia is an important complication associated with desmopressin use.

Excessive Cyclosporine-Associated Immunosuppression in a Dog Heterozygous for the MDR1 (ABCB1-1Δ) Mutation.

Pharmacodynamic monitoring was used to titrate cyclosporine dosing in a dog with immune-mediated hemolytic anemia. Development of a suspected secondary infection, with subsequent discovery of an unexpectedly high level of T-cell suppression despite a relatively low cyclosporine dose, prompted an investigation into the cause of possible excessive immunosuppression. Blood cyclosporine concentrations were within expected target ranges, and the dog was determined to be heterozygous for the multidrug resistance protein 1 (MDR1; ATP-binding cassette sub family B member 1-1Δ) gene mutation. The MDR1 mutation was suspected to have contributed to the excessive immunosuppression experienced by this patient. This case highlights the need to monitor immunosuppressive therapy in the individual patient, especially when the patient is not responding to therapy at typical dosages or when secondary infections develop at dosages lower than expected to cause significant immunosuppression. Pharmacodynamic monitoring can be used to help identify unexpected excessive immunosuppression in dogs receiving cyclosporine, and MDR1 genotyping should be further explored as a potential method of predicting and preventing its occurrence.

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.

Recovery of T-cell function in healthy dogs following cessation of oral cyclosporine administration.

Cyclosporine is a potent immunosuppressive agent used to treat immune-mediated disorders in dogs. Secondary infections sometimes necessitate withdrawal of cyclosporine, but it is not known how long it takes for the immune system to recover after cessation of cyclosporine. Our goal was to utilize a validated RT-qPCR assay in dogs to assess recovery time of the T-cell cytokines IL-2 and IFN-γ after discontinuation of cyclosporine. Six healthy dogs were given oral cyclosporine (10 mg/kg every 12 hr) for 1 week, with samples collected for measurement of cytokine gene expression prior to treatment, and on the last day of therapy. Cyclosporine was then discontinued, and samples were collected daily for an additional 7 days. Results revealed that there was a significant difference in cytokine expression when comparing pre-treatment and immediate post-treatment values, corresponding to marked suppression of T-cell function. There was no significant difference between pre-treatment values for either cytokine when compared with any day during the recovery period. Cytokine expression, evaluated as a percentage of pre-treatment baseline samples, demonstrated progressing return of T-cell function after drug cessation, with full recovery seen in all dogs by Day 4 of the recovery period.

Effects of pentoxifylline on whole blood IL-2 and IFN-gamma gene expression in normal dogs.

BACKGROUND: Pentoxifylline (PTX) is a methylxanthine phosphodiesterase inhibitor that is used as a hemorrheologic and anti-inflammatory agent in veterinary and human medicine. In human studies, PTX has been shown to decrease T-cell production of cytokines such as IL-2 and IFN-γ. A RT-qPCR assay to measure activated T-cell gene expression of IL-2 and IFN-γ has been validated in dogs. OBJECTIVES: The goal of this study was to utilize this assay to investigate the effects of PTX on in vitro cytokine gene expression in canine whole blood. METHODS: Whole blood from seven healthy dogs was collected and incubated with various concentrations of PTX for 1 hr before activation. PTX concentrations spanned and exceeded blood concentrations achieved when administered at clinically relevant dosages (1, 2, 10, 50 and 200 µg/ml). Cyclosporine was used at a concentration of 500 ng/ml as a positive control. All blood samples, including untreated activated baseline samples, were then activated with phorbol myristate acetate and ionomycin for 5 hrs. RESULTS: Analysis of activated whole blood by RT-qPCR revealed that there was not a significant suppression of IL-2 or IFN-γ gene expression at any concentration of PTX when evaluating ΔCt values. All samples exposed to cyclosporine showed significant changes from untreated activated baseline samples, demonstrating marked suppression as the positive control. Cytokine expression, presented as a percentage of untreated activated baseline samples, was also evaluated. After exposure to the highest concentration of PTX (200 µg/ml), median percentage cytokine expression was suppressed to just below 50% of baseline values. This concentration, however, is much higher than blood concentrations reported to be achieved at standardly used pentoxifylline doses. CONCLUSIONS: PTX does not appear to significantly suppress T-cell cytokine production in samples from most dogs at clinically relevant drug concentrations. Further testing is needed to establish the full effects of PTX on the immune system in dogs.

Effects of cyclosporine on feline lymphocytes activated in vitro.

Cyclosporine A (CsA) is a calcineurin inhibitor that is known to decrease lymphocyte expression of NFAT-regulated cytokines in humans, dogs and cats, and thereby depress lymphocyte function. Less is known about the effects of CsA on lymphocytes in cats than in other species. Peripheral blood mononuclear cells (PBMCs) were isolated from 6 healthy cats. PBMCs were exposed to i) no treatment, ii) 5 µg/ml concavalin A (ConA), iii) 500 ng/ml CsA and iv) 5 µg/ml ConA and 500 ng/ml CsA. The effects of CsA on cell proliferation were assessed via live and necrotic cell counts from day 1 to day 6. Additionally, flow cytometry was utilized to determine the effect of CsA on apoptosis in feline lymphocytes at day 1 and day 5. ConA exposure resulted in increases in cell counts from day 1 to 6, peaking at day 5. CsA inhibited cell proliferation, indicated via decreased live lymphocyte cell counts in the cell cultures exposed to ConA and CsA, compared to the cell cultures exposed to ConA only. Furthermore, CsA induced early and late apoptotic changes in feline PBMCs. Differences in these responses may influence an individual cat's response to cyclosporine therapy.

Coagulation factor activity in units of leukoreduced and nonleukoreduced canine fresh-frozen plasma.

OBJECTIVE: To evaluate coagulation factors in units of leukoreduced (LR) and nonleukoreduced (non-LR) canine fresh-frozen plasma (cFFP). ANIMALS: 8 healthy research dogs. PROCEDURES: In a crossover study, dogs were randomly assigned to 1 of 2 groups from which blood was collected and either did or did not undergo leukoreduction. After a recovery period of ≥ 28 days, the dogs were switched between protocols. After each collection, blood samples were centrifuged, and cFFP was stored frozen for later comparative analysis of coagulation factors, antithrombin, and protein C activities (reported as comparative percentages of the corresponding activities determined in a canine pooled plasma standard); prothrombin and activated partial thromboplastin times; and fibrinogen concentration. RESULTS: There were no significant differences detected between results for LR cFFP, compared with those for non-LR cFFP. CONCLUSIONS AND CLINICAL RELEVANCE: Although there was variation among residual activities of coagulation factors in LR and non-LR cFFP, the variations and differences were considered unlikely to impact the efficacy of LR cFFP transfused for coagulation factor replacement in dogs. However, owing to the small sample size and high variability of results in the present study, additional research with a larger sample size is required for definitive conclusions on the effects of leukoreduction on coagulation factors in cFFP and to develop treatment guidelines for LR cFFP use in dogs with congenital and acquired coagulopathies.

Assessment of erythrocyte damage and in-line pressure changes associated with simulated transfusion of canine blood through microaggregate filters.

OBJECTIVE: To determine whether passage of whole blood through a microaggregate filter by use of a syringe pump would damage canine erythrocytes. SAMPLE: Blood samples obtained from 8 healthy client-owned dogs. PROCEDURES: Whole blood was passed through a standard microaggregate filter by use of a syringe pump at 3 standard administration rates (12.5, 25, and 50 mL/h). Prefilter and postfilter blood samples were collected at the beginning and end of a simulated transfusion. Variables measured at each time point included erythrocyte osmotic fragility, mean corpuscular fragility, RBC count, hemoglobin concentration, RBC distribution width, and RBC morphology. In-line pressure when blood passed through the microaggregate filter was measured continuously throughout the simulated transfusion. After the simulated transfusion was completed, filters were visually analyzed by use of scanning electron microscopy. RESULTS: Regardless of administration rate, there was no significant difference in mean corpuscular fragility, RBC count, hemoglobin concentration, or RBC distribution width between prefilter and postfilter samples. Additionally, there were no differences in in-line pressure during the simulated transfusion among administration rates. Echinocytes were the erythrocyte morphological abnormality most commonly observed at the end of the transfusion at administration rates of 12.5 and 25 mL/h. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that regardless of the administration rate, the microaggregate filter did not alter fragility of canine RBCs, but may have altered the morphology. It appeared that the microaggregate filter would not contribute to substantial RBC damage for transfusions performed with a syringe pump.

Effects of cyclosporine and dexamethasone on canine T cell expression of interleukin-2 and interferon-gamma.

Cyclosporine and glucocorticoids are powerful immunosuppressive agents used to treat many inflammatory diseases in dogs. Cyclosporine inhibits calcineurin-dependent pathways of T cell activation and resultant T cell cytokine production, and glucocorticoids directly inhibit genes coding for cytokines. Little work has been done comparing the effects of these agents on T cell cytokine production in dogs. Our study measured T cell interleukin-2 (IL-2) and interferon-gamma (IFN-γ) production using flow cytometry and T cell IL-2 and IFN-γ gene expression using quantitative reverse transcription polymerase chain reaction (qRT-PCR) in activated canine T cells incubated with cyclosporine and dexamethasone in vitro. For flow cytometric assays, diluted whole blood was cultured for 7 h in the presence of cyclosporine (10, 100, 500, and 1000 ng/mL) or dexamethasone (10 ng/mL, 100 ng/mL, 1 µg/mL, and 10 µg/mL). For qRT-PCR, whole blood was cultured for 5 h with the same drugs at the same concentrations, and RNA was then extracted from leukocytes. Flow cytometry and qRT-PCR both demonstrated inhibition of IL-2 and IFN-γ that was concentration-dependent in response to cyclosporine, and was more variable for dexamethasone. Quantitative RT-PCR but not flow cytometry documented significant reduction of IL-2 expression after dexamethasone treatment, while both methods showed concentration-dependent suppression of IFN-γ. Quantitative RT-PCR also revealed additional cytokine suppression at higher cyclosporine concentrations, an effect not found using flow cytometry, and may therefore be the preferred method for cytokine determination in dogs. Suppression of IL-2 and IFN-γ in activated T cells may have potential as an indicator of the efficacy of cyclosporine and glucocorticoids in suppressing canine T cell function in vivo, and may therefore be of value for characterizing the immunosuppression induced by these drugs in clinical patients.

Alterations in activated T-cell cytokine expression in healthy dogs over the initial 7 days of twice daily dosing with oral cyclosporine.

Cyclosporine is a powerful T-cell inhibitor used in the treatment of immune-mediated and inflammatory diseases in the dog. There is limited information on how to best monitor patients on cyclosporine therapy. Currently, pharmacokinetic and pharmacodynamic assays are available. Pharmacokinetic assays that measure the concentration of cyclosporine in the blood are used to assess if an appropriate drug concentration has been achieved; however, target blood drug concentrations have not been shown to reliably correlate with suppression of T-cell function in the dog. In human transplant recipients, therapeutic drug monitoring has shifted to include pharmacodynamic-based monitoring. Our laboratory has validated a RT-qPCR assay to measure the pharmacodynamic effects of cyclosporine in the dog. In this study, activated T-cell expression of IL-2 and IFN-γ was measured using RT-qPCR daily for 7 consecutive days in 8 healthy Walker hounds receiving oral cyclosporine at a dosage of 10 mg/kg every 12 hr. Cytokine production was found to be markedly decreased within 24 hr after the initiation of cyclosporine and remained significantly decreased for the duration of the project. Based on these results, cyclosporine causes a rapid drop in T-cell cytokine production that is sustained with continued dosing in healthy dogs. Although performed in healthy dogs, this study demonstrated a marked decrease in cytokine suppression within 24 hr of drug administration, suggesting that pharmacodynamic monitoring of cyclosporine's effects on T cells could be considered within several days of commencing therapy in dogs suffering from life-threatening immune-mediated disorders.

Extraction and Analysis of Xylitol in Sugar-Free Gum Samples by GC-MS with Direct Aqueous Injection.

Xylitol, a sugar substitute frequently used in sugar-free gum, is generally considered harmless to humans but it can be extremely toxic to dogs. Dog-owning customers are becoming increasingly aware of the risks associated with xylitol-containing chewing gums. However, there remains some uncertainty if these chewing gums are still dangerous to dogs after they have been partially consumed. In this work, a reliable low-cost analytical method has been developed to quantify the xylitol in sugar-free gum samples. Xylitol was extracted from gum samples using water as a solvent. Extractions were analyzed by GC-MS with direct aqueous injection (DAI). This method was successfully applied to over 120 samples including fresh gum and 5 min, 15 min, and 30 min chewed gum samples.

Pharmacodynamic evaluation of the effects of oral melatonin on expression of the T-cell cytokines interleukin-2 and interferon gamma in the dog.

OBJECTIVE: To determine the effects of exogenous melatonin administration on activated whole blood expression of the T-cell cytokines interleukin-2 (IL-2) and interferon gamma (INF-γ) in dogs. ANIMALS: Ten healthy dogs. PROCEDURES: Heparinized whole blood was collected from 10 dogs for analysis of cytokine expression before administration of melatonin (baseline). Each dog was then administered melatonin at a dosage of approximately 1 mg/kg, PO, q 12 hr for 14 days. On day 14, whole blood was again collected from each dog at the time points of trough (0 hr) and 6 hr postmelatonin administration to evaluate the effects of melatonin on cytokine expression. At all evaluated time points, analysis of activated whole blood expression of mRNA coding for both IL-2 and IFN-γ was performed using quantitative reverse transcription polymerase chain reaction to determine whether a difference existed for any time point. Blood melatonin concentrations were also measured at comparable time points. RESULTS: A statistical difference in the expression of either cytokine was not appreciated at any time point, despite attainment of expected blood concentrations of the drug. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that melatonin therapy does not significantly affect IL-2 or IFN-γ expression in healthy dogs. While melatonin is thought to have an effect on the immune system in dogs, it does not appear this effect is through altering T-cell IL-2 or IFN-γ expression. Further studies investigating the effects of melatonin on the immune system of dogs are warranted.

Effect of immunosuppressive drugs on cytokine production in canine whole blood stimulated with lipopolysaccharide or a combination of ionomycin and phorbol 12-myristate 13-acetate.

A pharmacodynamic assay has been previously developed to monitor ciclosporin treatment in dogs by assessing inhibition of cytokine transcription after whole blood stimulation with 12-myristate 13-1 acetate and ionomycin (PMA/I). In this study, whole blood stimulation with either PMA/I or lipopolysaccharide (LPS) was used to assess the effect of multiple drugs (azathioprine, ciclosporin, mycophenolate, leflunomide and prednisone) after a 7-day treatment course on production of cytokines measured with a multiplex assay in healthy dogs (n = 4 for each treatment). Interleukin-10 (IL-10), interferon gamma (IFNγ) and tumour necrosis factor alpha (TNFα) were significantly activated by PMA/I stimulation and IL-6, IL-10 and TNFα by LPS stimulation, in the absence of immunosuppressive drugs. After ciclosporin treatment, IL-10, IFNγ and TNFα production was significantly reduced after stimulation with PMA/I compared to pre-treatment. After prednisone treatment, TNFα production was significantly reduced after stimulation with PMA/I or LPS compared to pre-treatment. No significant change was observed after treatment with azathioprine, leflunomide or mycophenolate. This methodology may be useful to monitor dogs not only treated with ciclosporin, but also with prednisone or a combination of both. Further studies are needed to assess the use of this assay in a clinical setting.