Cefadroxil in the horse: pharmacokinetics and in vitro antibacterial activity.

The research investigated the behavior and effects of the antibiotic cefadroxil in horses and tested its effectiveness against various bacterial strains. Main findings showed the cefadroxil had varying effectiveness depending on the bacterial strain and mode of administration in horses.

Research Method

• An antibiotic drug, Sodium cefadroxil, was administered as a single dose through the vein to six adult mares.
• The concentration of the drug in their plasma was measured over 24 hours using a microbiological assay.
• The distribution and removal of the drug from the body was modeled and key parameters calculated.
• In a separate experiment, a suspension of the drug was administered into the stomach of the same six horses.
• Samples were taken to measure peak plasma levels and absorption of the drug.

Pharmacokinetics of Cefadroxil

• Cefadroxil’s activity in the horse’s body was best described using a one-compartment open model. This is a standard model used in pharmacokinetics to describe the absorption, distribution, metabolism, and excretion of drugs.
• The main pharmacokinetic terms, which provide information about the drug action in the body, were identified. This includes the initial plasma concentration, half-life, volume of distribution, and body clearance rate.
• The drug’s half-life—a measure of how long it takes for half the drug to be removed from the body—was found to be 46 minutes on average.
• The other identified parameters were the initial plasma concentration (59.2 micrograms/ml), the volume of distribution (462 ml/kg), and the body clearance rate (7.0 ml/min.kg).

Antibacterial Activity of Cefadroxil

• The researchers tested the susceptibility of 99 bacterial strains from 11 species to cefadroxil. These bacteria were collected from horses suffering from clinical illnesses.
• The strains of bacteria demonstrated varying degrees of susceptibility to the antibiotic. Streptococcus equi, Streptococcus zooepidemicus, coagulase-positive staphylococci, Corynebacterium pseudotuberculosis, and most strains of Actinobacillus suis were highly susceptible to cefadroxil.
• However, some strains such as Escherichia coli, Klebsiella pneumoniae, and Salmonella sp. showed intermediate susceptibility and others including Corynebacterium (Rhodococcus) equi, Enterobacter cloacae and Pseudomonas aeruginosa proved to be highly resistant to cefadroxil.
• This finding allows for selection of this antibiotic in case of infections with these susceptible bacteria, while alternative treatments would need to be considered against the cefadroxil-resistant strains.