J vet Pharmacol Therap. 2018;1–5. wileyonlinelibrary.com/journal/jvp | 1 © 2018 John Wiley & Sons Ltd Thiamphenicol (TP) and its fluorinated derivative florfenicol (FF) are antimicrobials widely used in veterinary medicine. They act by binding to the 50S ribosomal subunit, leading to inhibition of pro- tein synthesis and bacteriostatic effect. FF and TP are used in a broad spectrum of infections caused by, for example., Pasteurella multocida, Staphylococcus aureus, Haemophilus sp., Bacteroides sp., and Streptococcus sp. in companion animals, farm animals and fish (Beers, Schoutens, Vanderlinden, & Yourassowsky, 1975; Switala & Debowy, 2005; Wei, Shien, Chang, & Chou, 2016; Wei et al., 2016; Yoshimura, Takagi, Ishimura, & Endoh, 2002). Pharmacokinetics (PK) of these two agents were described in cattle (Abdennebi, Sawchuk, & Stowe, 1994; Varma, Adams, Powers, Powers, & Lamendola, 1986), pigs (Haritova, Lashev, & Pashov, 2002; Jiang, Zeng, Chen, Liu, & Fung, 2006), rabbits (Abd El-Aty, El-Sooud, & Goudah, 2001; Park, Lim, Kim, Hwang, & Yun, 2007), dogs (Castells et al., 1998; Park, Lim, Kim, Hwang, & Yun, 2008), and sheep (Abdennebi, Khales, Sawchuk, & Stowe, 1994; Jianzhong, Xiubo, Haiyang, & Walter, 2004). As for birds, the scientific literature is rich in studies on FF PK in chickens (Afifi & Elsooud, 1997; Chang et al., 2010; Shen, Hu, Wu, & Coats, 2003) and turkeys (Switala et al., 2007; Watteyn, Croubels, De Baere, De Backer, & Devreese, 2018). Ismail and El-Kattan (2009) investigated FF kinetics in pigeons and quail while El-Banna (1998) assessed it in healthy and Pasteurella- infected ducks following intravenous (IV) and intramuscular injec- tion. The latter study, however, was carried out using microbiological assay which has significant drawbacks compared with chromato- graphic techniques (Marzo & Dal Bo, 1998). The literature on TP in poultry is limited to PK in chickens (Chen & Pu, 2008) and turkeys (Switala et al., 2007). There are no available data on TP PK in ducks. Considering physiological differences between waterfowl and other birds (Dorrestein & Vanmiert, 1988), it seems that simple extrapola- tion of dosage protocols from terrestrial birds to ducks may not be justified. Therefore, the aim of the study was to compare FF and TP PK in ducks after single IV and oral (PO) administration. Received: 23 May 2018 | Revised: 8 August 2018 | Accepted: 22 August 2018 DOI: 10.1111/jvp.12714 SHORT COMMUNICATION Pharmacokinetics of florfenicol and thiamphenicol in ducks Marta Tikhomirov | Błażej Poźniak | Andrzej Smutkiewicz | Marcin Świtała Department of Pharmacology and Toxicology, Faculty of Veterinary Medicine, Wrocław University of Environmental and Life Sciences, Wrocław, Poland Correspondence Marta Tikhomirov, Department of Pharmacology and Toxicology, Faculty of Veterinary Medicine, Wrocław University of Environmental and Life Sciences, Wrocław, Poland. Email: marta.tikhomirov@upwr.edu.pl Funding information Ministry of Science and Higher Education of the Republic of Poland – KBN, Grant/Award Number: 3 PZ6K 03724 Abstract The pharmacokinetics of florfenicol (FF) and thiamphenicol (TP) after single intrave- nous (IV) and oral (PO) administration was investigated in Mulard ducks. Both antibi- otics were administered at a dose of 30 mg/kg body weight, and their concentrations in plasma samples were assayed using high-performance liquid chromatography with ultraviolet detection. Pharmacokinetic parameters were calculated using a noncom- partmental method. After IV administration, significant differences were found for the mean residence time (2.25 ± 0.21 hr vs. 2.83 ± 0.50 hr for FF and TP, respec- tively) and the general half-life (1.56 ± 0.15 hr vs. 1.96 ± 0.35 hr for FF and TP, re- spectively) indicating slightly slower elimination of TP as compared to FF. The clearance, however, was comparable (0.30 ± 0.07 L/hr/kg for FF and 0.26 ± 0.04 L/ hr/kg for TP). The mean volume of distribution was below 0.7 L/kg for both drugs. Pharmacokinetics after PO administration was very similar for FF and TP suggesting minor clinical importance of the differences found in the IV study. Both antimicrobi- als showed rapid absorption and bioavailability of more than 70% indicating that PO route should be an efficient method of FF and TP administration to ducks under field conditions. KEYWORDS antimicrobials, ducks, florfenicol, pharmacokinetics, thiamphenicol