The U.S. Food and Drug Administration has approved Excede sterile suspension, a new long-acting antibiotic formulation for horses from Pfizer Animal Health, the company announced in a release.

Excede Sterile Suspension is used to treat lower respiratory tract infections in horses caused by susceptible bacterial strains of Streptococcus equi ssp. zooepidemicus. Excede acts as a sustained release product that offers an extended duration of action with fewer injections compared to other antibiotic treatments on the market. Veterinarians administer two intramuscular injections to affected horses 4 days apart. Therapeutic drug concentrations against Streptococcus equi ssp. zooepidemicus are maintained for a total of 10 days from the initiation of treatment.

"Excede Sterile Suspension has been used by veterinarians for many years with great success in cattle and swine," said Thomas Lenz, DVM, senior director of Equine Veterinary Services. "Pfizer Animal Health is excited to be able to offer this safe and effective antibiotic for treatment in horses in just two doses for a full course of therapy."

Excede Sterile Suspension is a cephalosporin antibiotic in the form of ceftiofur crystalline free acid. Ceftiofur, like other β-lactam antimicrobials, exerts a bactericidal effect by inhibiting bacterial cell wall synthesis. This interference is due primarily to covalent binding to the penicillin-binding proteins, which are essential for synthesis of the bacterial wall. After intramuscular injection, ceftiofur is released from the crystalline form in oil over time, and then rapidly metabolized to desfuroylceftiofur, the primary active metabolite. Ceftiofur is the only cephalosporin approved for use in horses and is known for its low toxicity and high margin of safety