Minocycline pharmacokinetics and pharmacodynamics in dogs: dosage recommendations for treatment of meticillin-resistant Staphylococcus pseudintermedius infections.
BACKGROUND
Although minocycline is not licensed for use in dogs, this tetracycline has therapeutic potential against meticillin-resistant Staphylococcus pseudintermedius.


OBJECTIVE
The aim of this study was to establish rational dosage recommendations for minocycline use in dogs. Specific objectives were to generate and analyse minocycline pharmacokinetic (PK) data on plasma and interstitial fluid (ISF) concentrations, plasma protein binding and pharmacodynamic (PD) data on antimicrobial activity against S. pseudintermedius.


METHODS
Six healthy dogs from a research colony were used in this study.


METHODS
Dogs were administered 5 mg/kg intravenously and 10 mg/kg orally (p.o.) of minocycline hydrochloride in separate crossover experiments. In vivo drug concentrations in plasma and in ISF collected by ultrafiltration were measured by high-performance liquid chromatography. Pharmacokinetic analysis was performed on plasma and ISF concentrations. PK/PD analysis was completed using in vitro data on plasma protein binding and minocycline susceptibility in 168 S. pseudintermedius isolates.


RESULTS
Minocycline distributed to the ISF to a higher degree than predicted by the protein-unbound fraction in plasma. A large volume of distribution after oral administration, with plasma and ISF elimination half-lives of 4.1 and 7.4 h, respectively, demonstrated that the ISF serves as a drug reservoir for sustained tissue concentrations. Monte Carlo simulation, used to assess target attainment at different drug dosages, indicated that p.o. administration of 5 mg/kg twice daily is sufficient to inhibit S. pseudintermedius strains with minimal inhibitory concentrations ≤0.25 μg/mL.


CONCLUSIONS
Besides dosage recommendations for therapy of meticillin-resistant Staphylococcus pseudintermedius infections in dogs, the study also provides PK/PD data necessary to consider species-specific clinical breakpoints for minocycline susceptibility testing.
Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark.
Marit G
MG
Maaland
Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark.
Luca
L
Guardabassi
College of Veterinary Medicine, North Carolina State University, 1060 William Moore Drive, Raleigh, North Carolina, 27607, USA.
Mark G
MG
Papich
D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology; D019540:Area Under Curve; D018592:Cross-Over Studies; D004283:Dog Diseases / Q000188:drug therapy / Q000382:microbiology*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D006207:Half-Life; D016106:Methicillin Resistance; D008911:Minocycline / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D013207:Staphylococcal Skin Infections / Q000188:drug therapy / Q000662:veterinary*; D013210:Staphylococcus / Q000187:drug effects*; D014018:Tissue Distribution
D000900:Anti-Bacterial Agents; D008911:Minocycline