Assessment of parasitological findings in heartworm-infected beagles treated with Advantage Multi® for dogs (10% imidacloprid + 2.5% moxidectin) and doxycycline.

BACKGROUND: Anecdotal reports support the position that the adulticidal heartworm treatment utilizing doxycycline and Advantage Multi®/Advocate® for Dogs (10% imidacloprid + 2.5% moxidectin) has successfully converted antigen-positive dogs to antigen-negative. To date, no controlled experimental studies have demonstrated the adulticidal efficacy of this treatment regimen. The aim of this study was to evaluate the parasitological and clinical efficacy of Advantage Multi® for Dogs (IMD + MOX) and doxycycline in heartworm-infected beagles. METHODS: This study utilized 16 dogs, 8 dogs in each of non-treated control and treated groups. A total of 16 adult Dirofilaria immitis (Missouri strain) were surgically transplanted into the jugular vein of each study dog. The treatment regimen of monthly IMD + MOX topically (per labeled dosage and administration) for 10 months and 10 mg/kg doxycycline BID orally for 30 days was initiated 30 days post-surgical transplant. Echocardiograms, radiographs, complete blood counts, clinical chemistry profiles, heartworm antigenemia and microfilaremia were evaluated every 4 weeks. Serum samples were assayed for heartworm antigen using the DiroCHEK® heartworm antigen test. The DiroCHEK® was performed according to the manufacturer's recommendations and read using a spectrophotometer at 490 nm. RESULTS: All dogs tested positive for the presence of heartworm antigen post-surgical transplant and prior to treatment. Heartworm antigen levels began declining in treated dogs 3 months post-treatment. Non-treated control dogs remained antigen-positive. No microfilariae were detected in treated dogs after 21 days post-treatment. At necropsy, adult heartworms were recovered from all non-treated control dogs with a range of 10-12 adult worms/dog for an average recovery of 10.6 adult heartworms/dog. In the IMD + MOX- and doxycycline-treated dogs, the range of adult heartworms recovered was 0-2 adult worms/dog, with five dogs having no adult heartworms present. The average adult heartworm recovery was 0.6/dog in the treated group. This treatment regimen demonstrated a 95.9% efficacy in eliminating adult heartworms (P < 0.0001). CONCLUSIONS: This study demonstrated that this treatment regimen successfully eliminated D. immitis microfilariae by 21 days post-treatment, reduced heartworm antigen concentration over time, and had a 95.9% efficacy in the elimination of mature adult heartworms. Based on this study, we conclude that this treatment regimen is a relatively quick, reliable and safe option to treat canine heartworm infection as compared to other treatment regimens involving macrocyclic lactones, when the approved drug melarsomine dihydrochloride is unavailable, contraindicated or declined by an owner unable to afford the more costly treatment or concerned about the potential side effects.

Efficacy of four commercially available heartworm preventive products against the JYD-34 laboratory strain of Dirofilaria immitis.

BACKGROUND: Heartworm disease in dogs can be severe and life threatening. Resistance to available heartworm preventives was considered among potential causes of increased reports of failed heartworm prevention in dogs. The objective of the present study was to compare the efficacy of four commercially available heartworm disease preventives against the JYD-34 strain of D. immitis. METHODS: Forty laboratory-reared dogs approximately 6 months old were used. Each dog was infected with fifty, third-stage heartworm larvae on study day (SD) -30. On SD-1, the dogs were randomized to five groups of eight dogs each. On SD-0, dogs in groups 1-4 were treated as follows: Group 1: ivermectin/pyrantel pamoate chewable tablets; Group 2: milbemycin oxime/spinosad tablets; Group 3: selamectin topical solution; and Group 4: imidacloprid/moxidectin topical solution. Dogs in Group 5 were not treated and served as controls. The dogs were treated according to their current body weights and labelled dose banding for each product. Groups 1, 2, and 3 were retreated with their respective products and current body weights on SD 31 and 60. On SDs 124-126 the dogs were euthanized and necropsied for recovery of adult heartworms. RESULTS: Adult heartworms were recovered at necropsy from each of the dogs in the control group (13-32 worms/dog, geometric mean (GM) = 18.4 worms/dog). Adult heartworms and/or worm fragments were also recovered from each of the dogs treated with ivermectin/pyrantel pamoate, milbemycin oxime/spinosad or selamectin. Geometric means of worms recovered from dogs in each of these groups were 13.1, 8.8, and 13.1, resulting in efficacies compared to controls of 29.0, 52.2, and 28.8 %, respectively. All dogs in Group 4 (imidacloprid/moxidectin) were free of adult heartworms (100 % efficacy). CONCLUSIONS: The combination of imidacloprid/moxidectin was 100 % effective in this study in preventing development of JYD-34 laboratory strain of D. immitis in dogs following a single treatment, while three monthlytreatments of the three other commercial products provided less than 100 % efficacy. The high efficacy achieved with imidacloprid/moxidectin was likely due to the unique pharmacokinetic properties of the topical formulation delivering greater and sustained drug concentrations necessary to prevent development of D. immitis larvae.

Pharmacokinetics and pharmacodynamics of rivaroxaban and its effect on biomarkers of hypercoagulability in patients with chronic heart failure.

BACKGROUND: Heart failure (HF) is associated with a hypercoagulable state that predisposes to thromboembolism and anti-coagulation may improve clinical outcomes. The oral, direct Factor Xa inhibitor, rivaroxaban, has not been studied in patients with HF. We hypothesized that rivaroxaban would also reduce biomarkers of hypercoagulability in patients with HF. METHODS: This study consisted of two cohorts: Cohort 1, open-label, actively controlled with enoxaparin 40 mg once daily, included 8 patients with acute decompensated HF; Cohort 2, double-blind and placebo-controlled, included 18 patients with stable, severe New York Heart Association Class III/IV HF. RESULTS: The pharmacokinetics (PK) and pharmacodynamics (PD) of rivaroxaban were similar across both cohorts. Biomarker assessments were performed in Cohort 2; prothrombin fragment 1.2 (F1.2) mean concentration decreased by 2.7 ng/ml over 7 days with rivaroxaban, and increased by 11.6 ng/ml with placebo, an absolute difference of 14.3 ng/ml (p = 0.0009). A non-significant reduction in rate of increase of D-dimer (DD) and thrombin-anti-thrombin complex (TAT) levels with rivaroxaban was observed over 7 days (p = 0.31 and p = 0.77, respectively). CONCLUSION: Rivaroxaban has similar PK/PD in patients with either acute or chronic HF. In vivo, hypercoagulability biomarkers appear to increase over time. Rivaroxaban reversed this trend for F1.2, and may reduce the rate of increase of DD and TAT in patients with stable, severe HF.

Antithrombotic therapies in patients with heart failure: hypothesis formulation from a research database.

PURPOSE: Heart failure is a significant public health problem. The present study is intended to explore in a research database whether antithrombotic therapies (ATTs) affect cardiovascular outcomes in patients with incident heart failure (IHF). METHODS: Using the United Kingdom Health Improvement Network research database, several multivariable models (including logistic and Cox's regression models, as well as propensity score methods) were used to examine all-cause mortality and clinical outcomes among five treatment groups. RESULTS: The cohort included 24,554 patients with IHF (50.2% men), with a mean age (standard deviation [SD]) of 76.4 (11.0) years. Nearly three-fourths of patients received at least one form of ATT. Patients receiving ATTs tended to be younger and more likely to be men, and had more cardiovascular comorbidities. During the 18-month follow-up period, the mortality rates were 11.1%, 14.6%, 17.8%, 19.5%, and 32.6% for warfarin combination therapy, warfarin alone, clopidogrel therapy, aspirin (ASA) alone, and no therapy, respectively, yielding odds ratios (95%confidence intervals [CI]) relative to no therapy of 0.28 (0.24, 0.33), 0.38 (0.34, 0.43), 0.46 (0.40, 0.52), and 0.49 (0.45, 0.53) for each therapy group, accordingly. The use of ATTs also appeared to be associated with a reduced risk for ischemic or thrombotic events. CONCLUSIONS: These data contribute to the formulation of the hypothesis that use of ATTs in clinical practice decreases the risk of morbidity and mortality in patients with IHF, although findings require further confirmative studies.

Determination of plasma and skin concentrations of orbifloxacin in dogs with clinically normal skin and dogs with pyoderma.

Plasma and skin concentrations of orbifloxacin (Orbax tablets, Schering-Plough Animal Health) were assessed in 14 clinically normal dogs and 14 dogs with pyoderma following oral administration of the drug at 7.5 mg/kg once daily for 5 to 7 days. Skin biopsies and whole blood samples were obtained before dosing and at the time of the expected maximum concentration in skin (3 hours after dosing) on the first and on the fifth to seventh day of dosing. Skin biopsies and plasma were analyzed for orbifloxacin concentrations by high-performance liquid chromatography. Dogs with pyoderma had significantly higher mean skin concentrations of orbifloxacin within 3 hours of administration (Day 0: 7.80 +/- 3.40 mcg/g, Days 4 to 6: 9.47 +/- 6.23 mcg/g) than did dogs with normal skin (Day 0: 3.85 +/- 1.08 mcg/g, Days 4 to 6: 5.43 +/- 1.02 mcg/g). After dosing on Day 0 and after five to seven daily treatments, dogs with pyoderma had significantly higher mean orbifloxacin skin:plasma ratios (1.40 and 1.44, respectively) than did clinically normal dogs (0.81 and 0.96, respectively). The accumulation of orbifloxacin in diseased skin may contribute to the efficacy of this compound for the treatment of bacterial skin infections.