J. Vet. Med. zyxwvuts A. zyxwvutsr 42, 177-183 zyxwvu (1995) zyxwvut @ 1995 Blackwell Wissenschafts - Verlag, Berlin ISSN 0931-184X zyxwvutsrq Catedra de Farmacologia, Facultad de Veterinaria, Uniwersidad Complutense de Madrid, Spain Comparison of the Kinetics of Sodium Meclofenamate Versus Meclofenamic Acid after Oral Administration to Sheep T. ENCINAS, E. VINAGRE, J. C. BOGGIO, M. L. DE VICENTE, M. I. SAN ANDRES and C. RODRIGUEZ Address of authors: Dra. Teresa Encinas Cerezo, Citedra de Farmacologia, Facultad de Veterinaria, Universidad Complutense de Madrid, Avda. Puerta de Hierro s/n 28040, Madrid, EspGa With 2 figures and 1 table (Received for publication July 8, 1994) Summary Meclofenamates are non-steroidal anti-inflammatory agents used in ruminants for the prevention and the treatment of anaphylactic processes. The objective of the present work was to study possible kinetic variations due to the chemical form of meclofenamates administered by the oral route to adult sheep. Six Rubia del Molar female sheep (2-3 years old, 47-57 kg) were used. Initially, an intravenous administration of sodium meclofenamate (2.2 mg/kg bwt) was given; the obtained kinetic results were in agreement with data from other authors. Oral administrations (20 mg/kg bwt) of sodium meclofenamate and meclofenamic acid were then given. When the reticular groove was opened, both drug forms showed a single meclofenamate plasma peak; tZmu were 60.0 -C 10.61 min and 127.50 -C 22.5 min for the sodium and acid form, respectively. The elimination rate constants zyxwv (B) were not significantly different, but the absorption half-lives were (14.69 -C 3.21 min for the sodium form and 61.07c 21.7 min for the acid form). The bioavailability was 48.6 k 4.3% for sodium meclofenamate and 65.1 zy f 2.8% for meclofenamic acid. Thus, the chemical form (sodium versus acid) alters the oral bioavailability and t, of meclofenamates in adult sheep. These findings agree with the behaviour of meclo- fenamates in man. Introduction Meclofenamic acid [N-(2,6 dichloro-m-tolyl) anthranilic acid] and its sodium salt (sodium meclofenamate) are non-steroidal anti-inflammatory agents. These com- pounds have anti-inflammatory and antipyretic actions in horses and ruminants and may have clinical value in the treatment and prophylaxis of allergic diseases, mastitis and parturition induction in ruminants (WELLS et al., 1973; BURKA and SCARNELL, 1978; MITCHELL and FLINT, 1978; MITCHELL et al., 1990; LOHUIS et al., 1991). It has been demonstrated that the efficacy of meclofenamates was directly related to the plasma levels of the free drug (AITKEN et al., 1975). In human beings, the acid form U.S. Copyright Clearance Center Code Statement: 0931 - 184X/95/4203 - 0177$11.00/0