Pharmacokinetic study of meropenem in healthy beagle dogs receiving intermittent hemodialysis

Meropenem, a second carbapenem antimicrobial agent with a broad spectrum of activity, is used to treat sepsis and resistant‐bacterial infections in veterinary medicine. The objective of this study was to identify the pharmacokinetics of meropenem in dogs receiving intermittent hemodialysis (IHD) and to determine the proper dosing in renal failure patients receiving IHD. Five healthy beagle dogs were given a single i.v. dose of 24 mg/kg of meropenem and received IHD. The blood flow rate, dialysate flow, and ultrafiltration rate were maintained at 40 mL/min, 300 mL/min, and 40 mL/h, respectively. Blood samples were collected for 24 h from the jugular vein and from the extracorporeal arterial and venous line. Urine samples and dialysate were also collected. The concentrations of meropenem were assayed using HPLC/MS/MS determination. The peak plasma concentration was 116 ± 37 μg/mL at 15 min. The systemic clearance was 347 ± 117 mL/h/kg, and the steady‐state volume of distribution was 223 ± 67 mL/kg. Dialysis clearance was 71.1 ± 34.3 mL/h/kg, and the extraction ratio by hemodialysis was 0.455 ± 0.150. The half‐life (T_1/2) in dogs with IHD decreased compared with those without IHD, and the reduction in T_1/2 was greater in renal failure patients than in normal patients. Sixty‐nine percent and 21% of the administered drug were recovered by urine and dialysate in the unchanged form, respectively. In conclusion, additional dosing of 24 mg/kg of meropenem after dialysis could be necessary according to the residual renal function of the patient based on the simulated data.     

Serum,milk, and tissue monensin concentrations in cattle with adequate and potentially toxic dietary levels of monensin: pharmacokinetics and diagnostic interpretation

Used in both beef cattle and dairy cows, monensin can provide many health benefits but can, when unintended overexposures occur, result in adverse effects. Information on serum and tissue concentrations following overexposure and/or overt toxicosis which may aid in diagnostics and clinical outcome is lacking. The aim of this study was to determine concentrations of monensin in biological specimens following oral exposure for 10 days to an approved dose (1 mg/kg) and a higher dose (5 mg/kg) of monensin given daily on a body weight basis to 10 dairy cows. No deaths were reported; cows receiving 5 mg/kg showed early signs of toxicosis including depression, decreased feed intake, and diarrhea after 4 days of exposure. Histopathological findings were minimal in most cows. Pharmacokinetic modeling of the detected serum concentrations for the 1 and 5 mg/kg dose groups determined the C_max, T_max, and t_1/2λ to be 0.87 and 1.68 ng/mL, 2.0 and 1.0 h, and 1.76 and 2.32 days, respectively. Mixed regression models showed that the dose level and days since last dose were significantly associated with monensin concentrations in all four tissues, and with cardiac troponin levels. The high dose resulted in a significant elevation of monensin in tissues at approximately 4.7 times compared to the monensin concentrations in the tissues of animals from the low‐dose group. The cTnI concentrations in the high‐dose group were 2.1 times that of cTnI in the low‐dose group. Thus, the ability to diagnose monensin overexposure and/or toxicosis will improve from knowledge of biological monensin concentrations from this study.     

The screening and evaluation of herbs and identification of herbal combinations with anti-viral effects on Newcastle disease virus

1. A total of 25 “heat-clearing and detoxifying” herbs used in Chinese medicine were investigated for their cytopathic effects on the growth of Newcastle Disease virus (NDV) in a chicken fibroblast cell line.

2. The 5 herbs with the highest virus inhibitory effects were Herba agastaches, Flos chrysanthemi indici, Rhizoma anemarrhenae, Astragalus root and Baikal skullcap root and these were used in herbal formulations. Anti-NDV activities of 4 formulations were tested on the growth of NDV in the DF-1 fibroblast cell line.

3. Formulation II, containing Baikal skullcap root, Astragalus root, Anemarrhena rhizome (1:1:2) and formulation IV containing Anemarrhena rhizome, Astragalus root and Flos chrysanthemi indici (1:1:1), which had strong anti-NDV activity in vitro, were used to determine the in vivo inhibitory effects of NDV-infection in chickens. After treatment with the two formulations serum IgY titres against NDV were improved, and morbidity was reduced in the NDV-infected chickens.

4. The results suggest that the components in formulations II and IV acted synergistically to improve resistance to Newcastle disease and provide a basis for the developing an anti-NDV herbal medicine.

     

Precaecal phosphorus digestibility of inorganic phosphate sources in male broilers

1. The aim of this study, comprising two experiments, was (1) to determine in Experiment 1 the relationship of incremental dietary P (phosphorus) content on precaecal digestible P in male broilers and (2) to determine in Experiment 2 the precaecal P digestibility of various inorganic P sources at marginal levels of P supply.

2. In Experiment 1, a total of 260 male Ross 308 broilers were divided into groups of 10 birds per pen resulting in 8 replicates for treatment 1 and 6 replicates for treatments 2–4. Experimental diets were formulated to contain 4 incremental concentrations of digestible P by means of increasing concentrations of monocalcium phosphate (MCP). In the second experiment, 480-d-old male Ross 308 broilers were divided in groups of 12 birds per pen resulting in 16 replicates for the basal diet and 6 replicates for each test diet. A total of 4 inorganic P sources, MCP, monodicalcium phosphate (MDCP), dicalcium phosphate (DCP) and defluorinated phosphate (DFP) were added to the basal diet to determine the precaecal P digestibility. Three of the 4 inorganic P sources (MCP, MDCP and DCP) represented a mix of batches from different producers. At the end of both experiments, the chyme of the posterior part of the small intestine was collected. Digestibility of P and Ca was determined using titanium dioxide as indigestible marker.

3. In Experiment 1, a reduction in precaecal digestibility of P was observed above an estimated precaecal digestible dietary P concentration of 4.8 g/kg.

4. The precaecal P digestibility of the tested inorganic P sources in Experiment 2 was 78.3% for MCP, 59.0% for DCP, 70.7% for MDCP and 31.5% for DFP.

     

Ovarian remnant removal using minimally invasive laparoscopic techniques in four dogs

Four partially intact, female dogs with a median age of 6 · 5 years were presented to Angell Animal Medical Center for laparoscopic treatment of ovarian remnant syndrome. Dogs were positioned in dorsal recumbency and a three‐port laparoscopic technique was used to identify and remove en bloc any abnormal tissue in the area of the ovarian pedicles. None of the dogs required conversion to open coeliotomy and there were no major complications. Abnormal tissue, including granulosa thecal cell tumour (n = 1), was identified bilaterally in three dogs and unilaterally in one dog. Clinical signs associated with ovarian remnant syndrome resolved in all dogs following surgery.