Comparison of the kinetics of sodium meclofenamate versus meclofenamic acid after oral administration to sheep.

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; t2max were 60.0 +/- 10.61 min and 127.50 +/- 22.5 min for the sodium and acid form, respectively. The elimination rate constants (beta) were not significantly different, but the absorption half-lives were (14.69 +/- 3.21 min for the sodium form and 61.07 +/- 21.7 min for the acid form). The bioavailability was 48.6 +/- 4.3% for sodium meclofenamate and 65.1 +/- 2.8% for meclofenamic acid. Thus, the chemical form (sodium versus acid) alters the oral bioavailability and tmax of meclofenamates in adult sheep. These findings agree with the behaviour of meclofenamates in man.