Serum 25-hydroxyvitamin D concentrations and mortality in dogs with blastomycosis.

Blastomycosis is a prominent fungal disease in the United States. Vitamin D status has been found to be altered in critical illness and various infectious diseases. The objectives of this study were to compare serum 25-hydroxyvitamin D (25[OH]D) concentrations in dogs with blastomycosis and healthy controls, to assess the change in serum 25(OH)D concentrations in dogs with blastomycosis after 30 days of treatment, and to determine if baseline serum 25(OH)D concentrations in dogs with blastomycosis were associated with in-hospital, 30-day, or end-of-study mortality. In this prospective cohort study, 19 dogs newly diagnosed with blastomycosis had serum 25(OH)D concentrations measured with a commercially available validated radioimmunoassay at the time of diagnosis and 30 days after start of treatment. These values were compared to 24 healthy control dogs. Serum 25(OH)D concentrations at the time of diagnosis were lower in dogs with blastomycosis (median, 203 nmol/L; range, 31-590 nmol/L) than in clinically healthy control dogs (259.5 nmol/L, 97-829 nmol/L; P = 0.01). Despite clinical improvement, there was no significant change in serum 25(OH)D concentrations from baseline to 30-day follow-up. Dogs with baseline serum 25(OH)D concentrations <180.5nmol/L had a greater odds of death during hospitalization (odds ratio [OR], 15.0; 95% confidence interval [CI], 1.4-191.3; P = 0.04) and at 30 days follow-up (OR, 30.0; 95% CI, 2.5-366.7; P = 0.006). These findings highlight the need for further studies evaluating the prognostic value of vitamin D status in dogs with blastomycosis at diagnosis and throughout treatment and remission.

Glutathione-S-transferase-theta genotypes and the risk of cyclophosphamide toxicity in dogs.

The antineoplastic agent cyclophosphamide (CP) has dose-limiting side effects including sterile haemorrhagic cystitis (SHC), bone marrow (BM) suppression and gastrointestinal (GI) toxicity in dogs. The metabolites acrolein and phosphoramide that mediate these toxicities are glutathione-S-transferase (GST) substrates, and low functioning GST alleles are associated with CP toxicity in humans. The aim of this study was to determine whether variants in 2 canine GST genes, GSTT1 and GSTT5, were over-represented in dogs that developed CP toxicity. Dogs undergoing pulse or metronomic CP chemotherapy were recruited (n = 101) and genotyped for 6 GSTT1 polymorphisms and 1 GSTT5 6-bp deletion that leads to non-functional enzyme. Median cumulative CP dosages for dogs with SHC (1350 mg/m2 ) were significantly higher than for dogs with GI/BM toxicity (871 mg/m2 ) or no toxicity (991 mg/m2 ; P = .0012). Dogs with SHC were more likely to have had metronomic (84.2%, 16 of 19 SHC cases) vs pulse (15.8%, 3 of 19 SHC cases) CP dosing (P < .0001). All dogs with BM or GI toxicity (n = 30) had pulse chemotherapy. GSTT1 and GSTT5 variant allele frequencies were not significantly different in CP-treated dogs with SHC or GI/BM toxicity compared to dogs without documented adverse effects. Work is underway to identify which canine GSTs detoxify acrolein and phosphoramide, so that better tools are available to predict the risk of CP toxicity in dogs.

A single-nucleotide polymorphism in the canine cytochrome b5 reductase (CYB5R3) gene is associated with sulfonamide hypersensitivity and is overrepresented in Doberman Pinschers.

Canine sulfonamide hypersensitivity (HS) has been associated with a variant in the cytochrome b5 reductase gene (CYB5R3 729A>G), which encodes a drug-detoxifying enzyme. Study objectives were to determine variant allele frequency in Doberman Pinschers (DOBE), a breed which may be predisposed to sulfonamide HS, and to characterize the effects of CYB5R3 729G on gene expression and function. CYB5R3 729A>G allele frequencies were compared between DOBE (n = 24) vs. non-Doberman (non-DOBE; n = 60) dogs. CYB5R3mRNA expression, protein expression, and reduction of sulfamethoxazole hydroxylamine were compared between banked canine liver samples of 729AA vs. GG genotype. The 729G allele was overrepresented in DOBE (1.00) vs. non-DOBE dogs (0.567, p < .0001). mRNA and protein expressions as well as cyt b5 reductase activity were similar between livers of AA and GG genotype. All Doberman Pinschers in this study were homozygous for CYB5R3 729G, which could contribute to this breed's apparent predisposition to sulfonamide HS. However, CYB5R3 729G does not alter sulfamethoxazole detoxification capacity, so a direct role could not be demonstrated. It is possible that this marker is linked to another contributing variant.

Characterization of a low expression haplotype in canine glutathione S-transferase (GSTT1) and its prevalence in golden retrievers.

Glutathione S-transferase-theta (GSTT1) is a carcinogen detoxification enzyme, and low activity variants are associated with lymphoma in humans. We recently found a variant in the 3' untranslated region (UTR) of canine GSTT1, *101_102insT, which was predicted to change miRNA binding and was found in 5 of 17 golden retriever (GR) dogs with lymphoma but none of 14 healthy GRs. The aim of this study was to determine whether this variant led to decreased GSTT1 expression and was a discernible risk factor for lymphoma within the GR breed. On resequencing, *101_102insT appeared to be in complete linkage disequilibrium with 3 additional 3'UTR variants, leading to the inferred haplotype *3T>C; *101_102insT; *190C>A; *203T>C. In canine livers that were heterozygous for this variant haplotype, GSTT1 protein expression was significantly lower compared to the reference haplotype (densitometry .40 vs .64, P = .022), and GSTT1 transcript levels by qPCR were also significantly lower (fold difference .52, P = .012), without evidence of substantial allelic expression imbalance. The variant haplotype led to >50% decrease in expression in vitro (.31 ± .07 vs .64 ± .19; P = .019). We found no significant difference in minor allele frequencies between 71 GR dogs with lymphoma (MAF .162) and 33 healthy age-matched controls (MAF .136, P = .69). Our results indicate that the variant GSTT1 3'UTR haplotype containing *101_102insT reduces gene expression, which could lead to impaired carcinogen detoxification, but was not a detectable risk factor for lymphoma in GR dogs.

Plasma l-citrulline concentrations in l-arginine-supplemented healthy dogs.

INTRODUCTION: To determine whether oral l-arginine increases plasma [l-citrulline] in dogs. ANIMALS: Eleven healthy staff-owned dogs were used in this study. MATERIALS AND METHODS: Dogs (n = 3) were given l-arginine (50mg/kg PO q8h) for 7 days, and plasma [l-arginine] and [l-citrulline] were analyzed by high performance liquid chromatography at baseline (BL), steady state trough, and 0.5, 1, 1.5, 2, 4, 6, and 8 h after final dosing on day 7. Eleven dogs were then treated with 100mg/kg l-arginine PO q8h for 7 days, and [l-arginine] and [l-citrulline] were measured at BL, steady state trough, and at peak 4 hrs after dosing (T4 hrs). RESULTS: - Plasma [l-arginine] and [l-citrulline] peaked at T4 hrs on the 50mg/kg dosage. Target outcome, modeled after human study results, of a doubling of [l-arginine] and a 25-30% increase in [l-citrulline] from BL were not reached. After the 100mg/kg dosage, plasma [l-arginine] increased from a BL median of 160.1 µM (range, 100.2-231.4 µM) to a peak of 417.4 µM (206.5-807.3 µM) at T4 hrs, and plasma [l-citrulline] increased from a BL median of 87.8 µM (59.1-117.1 µM) to peak of 102.2 µM (47.4-192.6 µM) at T4 hrs. Ten of eleven dogs showed a doubling of plasma [l-arginine] and 4/11 dogs achieved 25-30% or greater increases in plasma [l-citrulline]. No adverse effects on heart rate or blood pressure were noted. CONCLUSIONS: - Oral l-arginine dosage of 100mg/kg q8h doubles plasma [l-arginine] in healthy dogs, but conversion to l-citrulline is quite variable. Further evaluation of this dosage regimen in dogs with pulmonary hypertension is warranted.

Urinary F2 -Isoprostanes in Cats with International Renal Interest Society Stage 1-4 Chronic Kidney Disease.

BACKGROUND: F2 -isoprostanes, a biomarker of oxidant injury, increase with advancing chronic kidney disease (CKD) in humans. In cats, the relationship between CKD and oxidative stress is poorly understood. OBJECTIVES: To determine whether cats with advancing CKD have increasing urinary F2 -isoprostanes. ANIMALS: Control cats without evidence of CKD (≥6 years old; n = 11), and cats with IRIS stage 1 (n = 8), 2 (n = 38), 3 (n = 21), and 4 (n = 10) CKD. METHODS: This was a prospective observational study. Urinary F2 -isoprostanes (specifically free 15-F2t -isoprostanes) normalized to urine creatinine (IsoPs) were compared among groups and tested for correlations with blood pressure, proteinuria, serum creatinine concentration, and urine specific gravity. The IsoPs also were compared between cats with and without hypertension or proteinuria, and in cats fed predominantly standard versus renal diets. RESULTS: Urinary IsoPs were increased, but not significantly, in cats with stage 1 CKD (median 263 pg/mg creatinine; range, 211-380) compared to controls (182 pg/mg; range, 80-348) and decreased significantly from stage 1 through advancing CKD (stage 2, 144 pg/mg; range, 49-608; stage 3, 102 pg/mg; range, 25-158; stage 4, 67 pg/mg; range, 26-117; P < .01). Urinary IsoPs were inversely correlated with serum creatinine (r = -0.66, P < .0001). CONCLUSION AND CLINICAL IMPORTANCE: Urinary IsoPs are significantly higher in early CKD (stage 1) compared to cats with more advanced CKD. Additional studies are warranted to characterize oxidative stress in cats with stage 1 CKD and determine whether early antioxidant treatments have a protective effect on CKD progression.

Opportunistic fungal infections in dogs treated with ciclosporin and glucocorticoids: eight cases.

Glucocorticoids are the standard of care for the treatment of immune-mediated disorders, and ciclosporin is increasingly being used off-label as an adjunct immunosuppressive drug in dogs. However, opportunistic infections can develop during combination immunosuppressive regimens. This case series describes atypical fungal infections in eight dogs treated with immunosuppressive dosages of glucocorticoids and ciclosporin. The median duration of combined treatment prior to the identification of fungal infection was 31 (range, 13 to 201) days, although two dogs received glucocorticoids for prolonged periods prior to the addition of ciclosporin. The estimated prevalence of serious fungal infections with this drug combination appears to be low (approximately 1 · 67%), but these infections led directly or indirectly to death or euthanasia in five of eight (63%) dogs. These cases highlight the need for frequent clinical monitoring of dogs receiving immunosuppressive dosages of glucocorticoids and ciclosporin.

Incidence, timing, and risk factors of azathioprine hepatotoxicosis in dogs.

BACKGROUND: The use of azathioprine (AZA) in dogs is limited by the development of hepatotoxicosis and cytopenias. HYPOTHESIS AND OBJECTIVES: To characterize the observed incidence, timing, and risk factors for AZA hepatotoxicosis in dogs treated clinically, and to determine the relationship between the development of hepatotoxicosis and cytopenias. ANIMALS: Fifty-two dogs treated with AZA with clinical and biochemical follow-up, with a subset of 34 dogs available for determination of changes in liver enzyme activities in serum. METHODS: Retrospective medical record review, from January 2009 through December 2013. RESULTS: Hepatotoxicosis (as defined by a >2-fold increase in serum ALT) was observed in 5 of 34 dogs (15%) within a median onset of 14 days (range, 13-22 days). Dogs had a median 9-fold increase in ALT and 8-fold increase in ALP, which stabilized or resolved with drug discontinuation or dose reduction. German shepherds were significantly over-represented (3 of 5 dogs with hepatotoxicosis; P = .0017). Thrombocytopenia or neutropenia were seen in 4 of 48 dogs with CBC follow-up (8% of dogs), but occurred significantly later in treatment (median onset, 53 days; range 45-196 days) compared to hepatotoxicosis (P = .016). CONCLUSIONS AND CLINICAL IMPORTANCE: These results support the routine monitoring of liver enzymes during the first 1-4 weeks of AZA treatment in dogs, with continued monitoring of the CBC. Additional studies are warranted to characterize the apparently higher risk of AZA hepatotoxicosis in German shepherds.

Serum biomarkers of clinical and cytologic response in dogs with idiopathic immune-mediated polyarthropathy.

BACKGROUND: Immune-mediated polyarthopathy (IMPA) is common in dogs, and is monitored by serial arthrocenteses. HYPOTHESIS/OBJECTIVES: Plasma C-reactive protein (CRP), interleukin-6 (IL-6), and CXCL8 (interleukin-8) would serve as noninvasive markers of joint inflammation in IMPA. ANIMALS: Nine client-owned dogs with idiopathic IMPA; 6 healthy controls. METHODS: Prospective study. Plasma CRP, IL-6, and CXCL8 were measured by ELISA at baseline, 2, and 4 weeks during treatment with prednisone at 50 mg/m(2) /day. Arthrocenteses, the canine brief pain inventory (CBPI), and accelerometry collars were used to assess joint inflammation, lameness, and mobility at all 3 time points. RESULTS: C-reactive protein concentrations were higher in IMPA dogs (median 91.1 µg/mL, range 76.7-195.0) compared with controls (median <6.3 µg/mL, <6.3-13.7; P = .0035), and were significantly lower at week 2 (10.6 µg/mL, <6.3-48.8) and week 4 (<6.3 µg/mL, <6.3-24.4; P < .001). C-reactive protein was correlated with median CBPI scores (r = 0.68; P = .0004), joint cellularity (r = 0.49, P = .011), and mobility by accelerometry (r = -0.42, P = .048). Plasma IL-6 concentrations were also higher in IMPA dogs (median 45.9 pg/mL), compared with controls (median <15.7 pg/mL; P = .0008). IL-6 was lower in IMPA dogs by week 4 (<15.7 pg/mL; P = .0099), and was modestly correlated with CBPI scores (r = 0.47, P = .023). CXCL8 did not differ significantly between IMPA and healthy dogs. CONCLUSIONS: Plasma CRP and IL-6 might be useful surrogate markers of synovial inflammation and disease activity in dogs with IMPA.

Short- and long-term cure rates of short-duration trimethoprim-sulfamethoxazole treatment in female dogs with uncomplicated bacterial cystitis.

BACKGROUND: Long-duration beta-lactam antibiotics are used for empirical treatment in female dogs with uncomplicated bacterial cystitis. However, women with bacterial cystitis are treated with short-duration potentiated sulfonamides because longer courses of beta-lactams result in lower cure and higher recurrence rates. HYPOTHESIS/OBJECTIVES: Short-duration potentiated sulfonamide treatment is more efficacious than long-duration beta-lactam treatment in achieving clinical and microbiological cures in female dogs with uncomplicated bacterial cystitis. ANIMALS: Thirty-eight client-owned female dogs. METHODS: Randomized, double-blinded, placebo-controlled clinical trial. Dogs were treated with TMP-SMX (15 mg/kg PO q12h for 3 days followed by a placebo capsule PO q12h for 7 days; Group SDS; n = 20) or cephalexin (20 mg/kg PO q12h for 10 days; Group LDBL; n = 18). Dogs were monitored for clinical and microbiological cure during treatment and at short- and long-term follow-up. RESULTS: No statistically significant differences were found between treatment groups in clinical cure rates after 3 days of treatment (89% SDS, 94% LDBL; P = 1.00) and 4 days (85% SDS, 72% LDBL; P = .44) or >30 days (50% SDS, 65% LDBL; P = .50) after conclusion of treatment or in microbiological cure rates 4 days (59% SDS, 36% LDBL; P = .44) or >30 days (44% SDS, 20% LDBL; P = .40) after conclusion of treatment. CONCLUSIONS AND CLINICAL IMPORTANCE: We did not identify a difference in cure rates between short-duration sulfonamide and long-duration beta-lactam treatments in female dogs with uncomplicated cystitis. Long-term cure rates in both treatment groups were low. In some female dogs, "uncomplicated" bacterial cystitis may be more complicated than previously recognized.

Serum and urine Blastomyces antigen concentrations as markers of clinical remission in dogs treated for systemic blastomycosis.

BACKGROUND: Serum and urine Blastomyces antigen concentrations can be used to diagnose blastomycosis in dogs. OBJECTIVES: Blastomyces antigen concentrations correlate with clinical remission in dogs during antifungal treatment, and detect disease relapse after treatment discontinuation. ANIMALS: 21 dogs with newly diagnosed blastomycosis monitored until clinical remission (Treatment Phase), and 27 dogs monitored over 1 year from the time of antifungal discontinuation or until clinical relapse (After Treatment Phase). METHODS: Prospective study. Dogs were monitored monthly during treatment and every 3 months after treatment discontinuation, with a complete history, physical exam, chest radiographs, and ocular exam. Urine and serum Blastomyces antigen concentrations were measured at each visit using a quantitative enzyme immunoassay. RESULTS: At enrollment in the Treatment Phase, Blastomyces antigen was positive in all 21 urine samples (100% sensitivity; 95% CI 85-100%), and in 18 of 20 serum samples (90% sensitivity; 95% CI 70-97%). At 2-4 months of treatment, urine antigen was more sensitive for clinically detectable disease (82%; CI 60-94%) than serum antigen (18%; CI 6-41%). The sensitivity of the urine test for clinical relapse was 71% (CI 36-92%), with close to 100% specificity (CI 84-100%) during after treatment surveillance in this population. CONCLUSIONS: Urine Blastomyces antigen testing has high sensitivity for active disease at the time of diagnosis and during treatment, and moderate sensitivity but high specificity for clinical relapse. Urine testing should be useful at the time of diagnosis, when treatment discontinuation is being considered, and anytime there is poor clinical response or suspicion of relapse.

Positive association between a glutathione-S-transferase polymorphism and lymphoma in dogs.

Glutathione-S-transferase enzymes (GSTs) play an important role in the detoxification of environmental carcinogens. Defective GST genotypes are over-represented in human cancers; in particular, low activity GSTT1 genotypes are risk factors for non-Hodgkin lymphoma. We hypothesized that defective GSTT1 genotypes would be associated with lymphoma risk in dogs. To address this, we resequenced the exons, splice junctions, and 3'-UTR of canine GSTT1 in dogs with lymphoma (n = 93) and age-matched unaffected dogs (n = 86). Of 27 canine GSTT1 variants identified, the I2+28 G>A was significantly associated with lymphoma [odds ratio (OR) 6.26, 95% confidence interval (CI), 1.77-22.2], with the AA genotype found in 18.3% of affected dogs but only 3.5% of controls (P = 0.002). This intronic variant was predicted to perturb GSTT1 mRNA splicing, and may increase lymphoma risk by impairing detoxification of environmental chemicals. Confirmation of this finding in a larger population of dogs may support the inclusion of GSTT1 genotyping in epidemiologic studies of canine lymphoma risk.

Evaluation of polymorphisms in the sulfonamide detoxification genes CYB5A and CYB5R3 in dogs with sulfonamide hypersensitivity.

BACKGROUND: Delayed hypersensitivity (HS) reactions to potentiated sulfonamide antimicrobials occur in both dogs and humans, and involve an intermediate hydroxylamine metabolite that is detoxified by cytochrome b(5) and NADH cytochrome b(5) reductase. HYPOTHESIS/OBJECTIVES: We hypothesized that polymorphisms in the genes (CYB5A and CYB5R3) encoding these 2 enzymes would be associated with risk of sulfonamide HS in dogs. ANIMALS: A total of 18 dogs with delayed HS to potentiated sulfonamide antimicrobials and 16 dogs that tolerated (TOL) a therapeutic course of these drugs without adverse effect. METHODS: CYB5A and CYB5R3 were sequenced from canine liver, and the promoter, exons, and 3' untranslated regions of both genes were resequenced from genomic DNA obtained from all dogs. RESULTS: Multiple polymorphisms were found in both genes. When controlled for multiple comparisons, the 729GG variant in CYB5R3 was significantly overrepresented in dogs with sulfonamide HS (78% of dogs), compared to TOL dogs (31%; P = .003). CONCLUSIONS AND CLINICAL IMPORTANCE: The CYB5R3 729GG variant may contribute to the risk of sulfonamide HS in dogs. Functional characterization of this polymorphism, as well as genotyping in a larger number of HS and TOL dogs, is warranted.

Antioxidant status in hyperthyroid cats before and after radioiodine treatment.

BACKGROUND: Reversible antioxidant depletion is found in hyperthyroid humans, and antioxidant depletion increases the risk of methimazole toxicosis in rats. OBJECTIVES: To determine whether abnormalities in concentrations of blood antioxidants or urinary isoprostanes were present in hyperthyroid cats, and were reversible after radioiodine treatment. To determine whether or not antioxidant abnormalities were associated with idiosyncratic methimazole toxicosis. ANIMALS: Hyperthyroid cats presented for radioiodine treatment (n = 44) and healthy mature adult control cats (n = 37). METHODS: Prospective, controlled, observational study. Red blood cell glutathione (GSH), plasma ascorbate (AA), plasma free retinol (vitamin A), α-tocopherol (vitamin E), and urinary free 8-isoprostanes in hyperthyroid cats were compared to healthy cats and to hyperthyroid cats 2 months after treatment. RESULTS: Blood antioxidants were not significantly different in hyperthyroid cats (mean GSH 1.6 ± 0.3 mM; AA 12.8 ± 4.9 µM, and vitamin E, 25 ± 14 µg/mL) compared to controls (GSH 1.4 ± 0.4 mM; AA 15.0 ± 6.6 µM, and vitamin E, 25 ± 17 µg/mL). Urinary isoprostanes were increased in hyperthyroid cats (292 ± 211 pg/mg creatinine) compared to controls (169 ± 82 pg/mg; P = .006), particularly in hyperthyroid cats with a USG < 1.035. Plasma free vitamin A was higher in hyperthyroid cats (0.54 ± 0.28 µg/mL versus 0.38 ± 0.21 in controls; P = .007). Both abnormalities normalized after radioiodine treatment. No association was found between oxidative status and prior idiosyncratic methimazole toxicosis. CONCLUSION AND CLINICAL IMPORTANCE: Increased urinary isoprostane could reflect reversible renal oxidative stress induced by hyperthyroidism, and this requires additional evaluation.

Retrospective comparison of the efficacy of fluconazole or itraconazole for the treatment of systemic blastomycosis in dogs.

BACKGROUND: Itraconazole is recommended for treatment of blastomycosis in dogs. Some evidence suggests that fluconazole might be less hepatotoxic than itraconazole. OBJECTIVES: To compare (1) incidence of clinical remission and death; (2) treatment duration; (3) total drug cost; (4) incidence of relapse; and (5) incidence of increased ALT activities in dogs with blastomycosis treated with fluconazole or itraconazole. ANIMALS: One hundred and forty-four dogs with systemic blastomycosis treated with itraconazole or fluconazole from 1998 to 2008. METHODS: Retrospective case review. Information obtained included signalment, body weight, clinical signs, drug regimen, treatment duration, time to clinical remission, and laboratory results. RESULTS: Neither treatment efficacy between fluconazole (75% remission) and itraconazole (90% remission) nor relapse rate (18% for itraconazole, 22% for fluconazole) was significantly different (P = .13, .75, respectively). Treatment duration was significantly longer for fluconazole (median 183 days) than for itraconazole (138 days; P = .001). Costs for fluconazole (median $1,223) were significantly less than for itraconazole ($3,717; P < .001). Incidence of increased ALT activities was not significantly different between groups (17% [3/18] for fluconazole, 26% [6/23] for itraconazole; P = .71). CONCLUSIONS: Fluconazole is associated with survival to clinical remission in 75% of dogs with blastomycosis. Although dogs receiving fluconazole were treated longer, drug costs were one-third those of itraconazole. Hepatotoxicosis, as estimated by increases in serum ALT activity, can be observed with similar incidence for both drugs.

Glutathione, cysteine, and ascorbate concentrations in clinically ill dogs and cats.

BACKGROUND: Oxidative stress plays a role in the pathogenesis of many systemic diseases. Hospitalized human patients are glutathione, cysteine, and ascorbate deficient, and antioxidant depletion has been correlated with poor clinical outcome. To date little is known about antioxidant concentrations in hospitalized veterinary patients. The purpose of this study was to determine whether ascorbate, cysteine, or glutathione depletion is present in ill dogs and cats compared with healthy controls. HYPOTHESIS: Clinically ill dogs and cats would be antioxidant depleted, and depletion would correlate with illness severity and clinical outcome. ANIMALS: Clinically ill client-owned dogs (n = 61) and cats (n = 37), healthy control dogs (n = 37) and cats (n = 33). METHODS: Prospective, observational, case control study. Erythrocyte reduced glutathione, plasma cysteine, and plasma ascorbate were quantified using high-performance liquid chromatography. RESULTS: Clinically ill dogs had significantly lower erythrocyte glutathione concentrations (1.22 mM, range 0.55-3.61) compared with controls (1.91 mM, range 0.87-3.51; P = .0004), and glutathione depletion correlated with both illness severity (P = .038) and mortality (P = .010). Cats had higher ascorbate concentrations when ill (10.65 microM, range 1.13-25.26) compared with controls (3.68 microM, range 0.36-13.57; P = .0009). CONCLUSIONS AND CLINICAL IMPORTANCE: Clinically ill dogs had decreased erythrocyte glutathione concentrations, which could be a marker of illness severity and prognostic of a poor outcome. Clinically ill cats had an unexpectedly high plasma ascorbate, which could represent a unique species response to oxidative stress.

Risk of hemolytic anemia with intravenous administration of famotidine to hospitalized cats.

BACKGROUND: Famotidine administered IV has been associated anecdotally with hemolysis in cats, and some veterinarians recommend using injectable famotidine only by the subcutaneous (SC) route for cats. However, the actual risk of such a reaction is not known. HYPOTHESIS: We hypothesized that famotidine, when given IV slowly, would not be associated with a clinically significant drop in packed cell volume (PCV) in hospitalized cats. ANIMALS: One hundred and forty-two hospitalized cats. METHODS: A retrospective medical record review was performed for hospitalized cats prescribed famotidine IV (n = 56), famotidine SC (n = 48), or no famotidine (n = 38) at a veterinary medical teaching hospital over the period from January 2004 through December 2006. RESULTS: Baseline signalment, observation times, and famotidine dosage (in treated cats) were similar among groups. Median baseline PCVs were significantly lower in the IV (31.5%) and SC (32.0%) groups compared with the control group (35.0%; P= .04). The median percent drop in PCV (3-4%), however, was no different in cats that received famotidine by either route compared with the control group (P= .90), and no cats in either famotidine group were observed to have any clinical signs of hemolysis. CONCLUSIONS AND CLINICAL IMPORTANCE: We conclude from this retrospective study that famotidine IV was given to 56 hospitalized cats without evidence of hemolysis, and that the IV route appeared safe when famotidine was administered over 5 minutes. We could not document a safety advantage of SC versus IV administration in this group of cats.

Anti-myeloperoxidase and anti-cathepsin G antibodies in sulphonamide hypersensitivity.

BACKGROUND: Anti-neutrophil cytoplasmic antibodies (ANCA) are associated with vasculitis in humans. Sulphonamide antimicrobials cause drug hypersensitivity (HS) reactions with some clinical signs that are suggestive of vasculitis. OBJECTIVE: The purpose of this study was to determine whether sulphonamide HS is associated with anti-neutrophil antibodies, using the dog as a spontaneous clinical model. METHODS: Thirty-four sulphonamide-HS dogs, 11 sulphonamide-'tolerant' dogs, and nine healthy sulphonamide-naïve dogs were evaluated for anti-neutrophil antibodies using a commercial ELISA against human myeloperoxidase (MPO), a commercial human ANCA Western blot protocol, and immunoblotting against whole canine neutrophils. RESULTS: Using ELISA, anti-MPO antibodies were found with an apparent higher frequency in HS dogs (50%), compared with 'tolerant' dogs (18%), which also showed significantly lower absorbances. Among HS dogs, anti-MPO antibodies were significantly more common, with significantly higher absorbances, in dogs that did not survive the HS reaction (78%) compared with survivors (35%). Using immunoblotting, ANCA were detected with similar overall frequencies in HS and 'tolerant' dogs. However, one protein targeted by several HS dogs, but no 'tolerant' dogs, was identified as cathepsin G. CONCLUSION: These data indicate that anti-MPO antibodies and anti-cathepsin G antibodies are associated with sulphonamide HS. Anti-MPO antibodies have been shown to be pathogenic both in vitro and in vivo, leading to vasculitis lesions and vasculitis-like syndromes. The present study therefore suggests that vasculitis might be one mechanism of tissue damage in this sulphonamide HS. Furthermore, the evaluation of ANCA, and its relationship to disease severity and clinical outcome, should be considered in human patients with sulphonamide drug HS.

Association of drug-serum protein adducts and anti-drug antibodies in dogs with sulphonamide hypersensitivity: a naturally occurring model of idiosyncratic drug toxicity.

BACKGROUND: Sulphonamide antimicrobials, such as sulphamethoxazole (SMX), provide effective infection prophylaxis in immunocompromised patients, but can lead to drug hypersensitivity (HS) reactions. These reactions also occur in dogs, with a similar time course and clinical presentation as seen in humans. OBJECTIVES: Drug-serum adducts and anti-drug antibodies have been identified in sulphonamide HS humans. The aim of this study was to determine whether similar markers were present in dogs with sulphonamide HS. METHODS: Thirty-four privately owned sulphonamide HS dogs, 10 sulphonamide-'tolerant' dogs, 18 sulphonamide-naïve dogs, and four dogs experimentally dosed with SMX and the oxidative metabolite SMX-nitroso, were tested for drug-serum adducts by immunoblotting, and anti-drug antibodies by ELISA. RESULTS: Sulphonamide-serum adducts were found in 10/20 HS dogs tested (50%), but in no tolerant dogs. Anti-sulphonamide IgG antibodies were detected in 17/34 HS dogs (50%), but in only one tolerant dog; antibody absorbance values were significantly higher in HS dogs. There was a significant association between the presence of sulphonamide-serum adducts and anti-sulphonamide antibodies (P = 0.009). Anti-drug antibodies were also found in dogs experimentally dosed with SMX-nitroso followed by SMX, but not in a dog dosed with drug vehicle, followed by SMX. CONCLUSION: Similar humoral markers are present in dogs and humans with sulphonamide HS, supporting the use of dogs as a naturally occurring model for this syndrome in humans. These data suggest the potential use of drug-serum adducts and anti-drug antibodies as markers for sulphonamide HS. Preliminary data indicate that anti-sulphonamide antibodies may be triggered by the SMX-nitroso metabolite, not by the parent drug, in dogs.