Short Communication Pharmacokinetic behaviour of enrofloxacin in greater rheas following a single-dose intramuscular administration Jose ´ Julio de Lucas a , Joaquı ´n Luis Navarro b , Sonia Rubio a , Pablo Emilio Vignolo b , Vilma Carina Asis b , Fernando Gonza ´lez a , Casilda Rodrı ´guez a, * a Departamento de Toxicologı ´a y Farmacologı ´a, Facultad de Veterinaria, Universidad Complutense de Madrid, Spain b Centro de Zoologı ´a Aplicada, Universidad Nacional de Co ´ rdoba, Argentina Accepted 11 November 2006 Abstract The pharmacokinetic behaviour of enrofloxacin in greater rheas was investigated after intramuscular (IM) administration of 15 mg/ kg. Plasma concentrations of enrofloxacin and its active metabolite, ciprofloxacin, were determined by high performance liquid chroma- tography. Enrofloxacin peak plasma concentration (C max = 3.30 ± 0.90 lg/mL) was reached at 24.17 ± 9.17 min. The terminal half-life (t 1/2k ) and area under the curve (AUC) were 2.85 ± 0.54 h and 4.18 ± 0.69 lg h/mL, respectively. The AUC and C max for ciprofloxacin were 0.25 ± 0.06 lg/mL and 0.66 ± 0.16 lg h/mL, respectively. Taking into account the values obtained for the efficacy indices, an IM dose of 15 mg/kg of enrofloxacin would appear to be adequate for treating infections caused by highly susceptible bacteria (MIC 90 < 0.03 lg/mL) in greater rheas. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Pharmacokinetic; Enrofloxacin; Ciprofloxacin; Rhea; Intramuscular The Rheidae family is now part of the ratite food pro- duction industry. Bacterial diseases such as gastroenteritis, omphalitis, air sacculitis, sinusitis and septicemia are important causes of morbidity and mortality in rheas and young chicks have a much higher mortality rate (med- ian 50%) than adults (Navarro and Martella, 2002). The antimicrobial properties of enrofloxacin, a broad- spectrum fluoroquinolone antimicrobial agent, indicate that it might have advantages for use in these birds. In pre- vious studies, a low residence time, a fast elimination and a high volume of distribution were observed in rheas after intravenous (IV) administration of enrofloxacin (De Lucas et al., 2005). Information after intramuscular (IM) admin- istration is not however available although this route is commonly used in livestock species. The aim of the present study was to determine the pharmacokinetic profile and pharmacokinetic/pharmacodynamic integration of enro- floxacin and its active metabolite, ciprofloxacin, in young greater rheas following a single IM administration to assess whether the route could be a suitable therapeutic option in this species. Six healthy greater rheas (4–5 months of age, 3.35 ± 0.34 kg bodyweight) were used. The birds came from the experimental breeding farm (Centro de Zoologı ´a Aplicada) of the Universidad Nacional de Co ´rdoba (UCN), Argentina. The Institutional Ethics in Animal Experimentation Committee at the UCM approved the study. Enrofloxacin (Baytril 5% solution, Bayer) was injected IM at a single dose of 15 mg/kg in the iliotrochanteric-ilio- femoral muscles. Blood samples were collected from the right jugular vein at 0, 5, 10, 15, 30, 45, 60 and 90 min, and at 2, 3, 4, 6, 8, 10, 24 and 48 h after dosing. Plasma concentrations of enrofloxacin and ciprofloxacin were simultaneously quantified using high performance liquid chromatography u.v. (De Lucas et al., 2005). Linear cali- bration curves were obtained between 0.025–10 lg/mL 1090-0233/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.tvjl.2006.11.007 * Corresponding author. Tel.: +34 91 3943789; fax: +34 91 3943848. E-mail address: casilda@vet.ucm.es (C. Rodrı ´guez). www.elsevier.com/locate/tvjl Available online at www.sciencedirect.com The Veterinary Journal 175 (2008) 136–138 The Veterinary Journal