Cefadroxil in the horse: pharmacokinetics and in vitro antibacterial activity

Sodium cefadroxil was administered as a single intravenous dose (25 mg/kg) to six healthy adult mares. Plasma samples were collected over a 24-h period and cefadroxil concentrations were measured by microbiological assay. The pharmacokinetic behavior of the drug was appropriately described in terms of a one-compartment open model. Values for the major pharmacokinetic terms were: extrapolated initial plasma concentration = 59.2 +/- 15.0 micrograms/ml; half-life = 46 +/- 20 min; apparent volume of distribution = 462 +/- 191 ml/kg; and body clearance = 7.0 +/- 0.6 ml/min.kg. In a subsequent study, a suspension of cefadroxil monohydrate was administered intragastrically (25 mg/kg) to the same six horses. Plasma concentrations of the drug peaked at 1-2 h but, in general, absorption was both poor and inconsistent. The data were unsuitable for determination of cefadroxil bioavailability from this oral dosage form. Ninety-nine isolates of eleven bacterial species obtained from clinically ill horses were tested for susceptibility to cefadroxil. All strains of Streptococcus equi, Streptococcus zooepidemicus, coagulase-positive staphylococci, Corynebacterium pseudotuberculosis and five out of six strains of Actinobacillus suis were highly susceptible to the drug (MIC less than 4 micrograms/ml). Escherichia coli, Klebsiella pneumoniae and Salmonella sp. showed intermediate susceptibility (MIC 4-16 micrograms/ml), while all isolates of Corynebacterium (Rhodococcus) equi, Enterobacter cloacae and Pseudomonas aeruginosa proved to be highly resistant to cefadroxil (MIC greater than 128 micrograms/ml).     

Soil Solution Chemistry and Throughfall Under Adjacent Stands of Japanese Larch and Sitka Spruce at Three Contrasting Locations in Britain

Soil solution and throughfall chemistry were investigated inadjacent stands of Japanese larch and Sitka spruce at threesites in Britain. Throughfall was collected in open funnel collectorsand soil solution was collected using tensionless tray lysimetersat the base of the H horizon and ceramic cup suction samplersat the base of the B horizon. Sampling took place fortnightlyfor 14 months and samples were analysed for the major ions anddissolved organic carbon. Most ions were present in higher concentrationsunder spruce than larch. Most notably under the spruce at allsites SO₄ in throughfall and NO₃ Ca and Al in the B horizonwere present in greater concentrations. However there were notrends in fortnightly concentrations of any ion, associatedwith the presence and absence of needles on the larch. Whensolutes are expressed as fluxes the only consistent effect ofspecies on the B horizon is higher quantities of NO₃ and NH₄under spruce. The study suggests that in areas exposed to atmosphericpollution, thinned stands of larch could have a beneficial rolerelative to Sitka spruce, in the maintenance of low acidityand aluminium concentrations in drainage water.     

Drug metabolism in the newborn rabbit

A number of drugs that are metabolized through the action of enzymes present in liver microsomes in the adult rabbit are not metabolized in livers of newborn rabbits. The development of metabolic pathways during a period of 4 weeks is presented. Evidence is given for the presence in livers of baby rabbits of inhibitors of some of these drug-enzyme systems.     

A comparison between supplements to silage of high digestibility offered to dairy cows

Grass silage containing 180 g crude protein and 660g digestible organic matter per kg DM was offered to forty-two dairy cows for 20 weeks in a self-feeding system. In addition, supplements of either mineralized barley (130 g crude protein per kg DM) or barley plus groundnut (180 g crude protein per kg DM) were offered. The mean daily milk yields were 18·5 and 19·4 kg per cow respectively.