The pharmacokinetics of maropitant citrate dosed orally to dogs at 2 mg/kg and 8 mg/kg once daily for 14 days consecutive days.

The pharmacokinetics of maropitant were evaluated in beagle dogs dosed orally with Cerenia® tablets (Pfizer Animal Health) once daily for 14 consecutive days at either 2 mg/kg or 8 mg/kg bodyweight. Noncompartmental pharmacokinetic analysis was performed on the plasma concentration data to measure the AUC(0-24) (after first and last doses), Ct (trough concentration-measured 24 h after each dose), Cmax (after first and last doses), tmax (after first and last doses), λz (terminal disposition rate constant; after last dose), t(1/2) (after last dose), and CL/F (oral clearance; after last dose). Maropitant accumulation in plasma was substantially greater after fourteen daily 8 mg/kg doses than after fourteen daily 2 mg/kg doses as reflected in the AUC(0-24) accumulation ratio of 4.81 at 8 mg/kg and 2.46 at 2 mg/kg. This is most likely due to previously identified nonlinear pharmacokinetics of maropitant in which high doses (8 mg/kg) saturate the metabolic clearance mechanisms and delay drug elimination. To determine the time to reach steady-state maropitant plasma levels, a nonlinear model was fit to the least squares (LS) means maropitant Ct values for each treatment group. Based on this model, 90% of steady-state was determined to occur at approximately four doses for daily 2 mg/kg oral dosing and eight doses for daily 8 mg/kg oral dosing.

Pharmacokinetics of ceftiofur crystalline-free acid sterile suspension in the equine.

Absolute bioavailability and dose proportionality studies were performed with ceftiofur in horses. In the absolute bioavailability study, thirty animals received either an intravenous dose of ceftiofur sodium at 1.0 mg/kg or an intramuscular (i.m.) dose of ceftiofur crystalline-free acid (CCFA) at 6.6 mg/kg. In the dose proportionality study, 48 animals received daily i.m. ceftiofur sodium injections at 1.0 mg/kg for ten doses or two doses of CCFA separated by 96 h, with CCFA doses of 3.3, 6.6, or 13.2 mg/kg. Noncompartmental and mixed-effect modeling procedures were used to assess pharmacokinetics (PK). CCFA was well absorbed with a bioavailability of 100%. AUC(0-∞) and C(max) increased in a dose-related manner following administration of the two doses of CCFA at 3.3, 6.6, and 13.2 mg/kg. The least-squares mean terminal half-life (t(½) ) following the tenth daily i.m. injection of ceftiofur sodium at 2.2 mg/kg was 40.8 h, but the least-squares mean t(½) following the second i.m. injection of CCFA at 6.6 mg/kg was 100 h. The time that plasma ceftiofur equivalent concentrations remain above a threshold concentration of 0.2 µg/mL has been associated with efficacy, and following administration of two 6.6 mg/kg doses of CCFA, the mean time above 0.2 µg/mL was 262 h. Simulations with the nonlinear mixed-effect PK model predicted that more than 97.5% of horses will have plasma ceftiofur equivalent concentrations >0.2 µg/mL for 96 h after the second 6.6 mg/kg dose of CCFA.

The pharmacokinetics of mavacoxib, a long-acting COX-2 inhibitor, in young adult laboratory dogs.

The pharmacokinetics of mavacoxib were evaluated in an absolute bioavailability study, a dose-proportionality study and a multi-dose study in young healthy adult laboratory Beagle dogs and in a multi-dose safety study in Beagle-sized laboratory Mongrel dogs. When administered as the commercial tablet formulation at 4 mg/kg body weight (bw) to fasted dogs, the absolute bioavailability (F) of mavacoxib was 46.1%; F increased to 87.4% when mavacoxib was administered with food. Following intravenous administration, the total body plasma clearance of mavacoxib was 2.7 mL·h/kg, and the apparent volume of distribution at steady-state was 1.6 L/kg. The plasma protein binding of mavacoxib was approximately 98% in various in vitro and ex vivo studies. The dose-normalized area under the plasma concentration-time curve was similar in Beagle and Beagle-sized Mongrel dogs when mavacoxib was administered with food. Mavacoxib exhibited dose-proportional pharmacokinetics for single oral doses of 2-12 mg/kg in Beagle dogs and for multiple oral doses of 5-25 mg/kg in Beagle-sized Mongrel dogs. Only minor accumulation occurred when mavacoxib was administered at doses of 2-25 mg/kg bw orally to laboratory dogs with a 2-week interval between the 1st two doses but with a monthly interval thereafter. Across all three Beagle studies (n = 63) the median terminal elimination half-life (t(½) ) was 16.6 days, with individual values ranging 7.9-38.8 days. The prolonged t(½) for mavacoxib supports the approved regimen in which doses are separated by 2-4 weeks.

Pharmacokinetic properties of toceranib phosphate (Palladia, SU11654), a novel tyrosine kinase inhibitor, in laboratory dogs and dogs with mast cell tumors.

Toceranib phosphate (Palladia, SU11654), an oral tyrosine-kinase inhibitor, is under investigation for the treatment of mast cell tumors in dogs. The pharmacokinetics of toceranib phosphate has been characterized in dogs. Means of the following pharmacokinetic parameters were estimated following a 1.0 mg/kg i.v. dose to laboratory beagles: plasma clearance of 1.45 L/kg/h, volume of distribution of 29.7 L/kg, and terminal half-life of 17.7 h. Following single oral doses of 3.25 mg/kg administered to laboratory beagles, mean C(max) estimates ranged from 68.6 ng/mL to 112 ng/mL with t(max) ranging from 5.3 h and 9.3 h postdose. Terminal half-life was estimated at 31 h. Oral bioavailability was 76.9%. There were no statistically significant (P > 0.05) differences with any pharmacokinetic parameter due to fed/fasted state or with time during 13 weeks of every-other-day dosing at 3.25 mg/kg. Toceranib concentrations were proportional with dose over the range of 2.0 to 6.0 mg/kg. The pharmacokinetics of toceranib in client-owned dogs of a variety of pure and mixed breeds with mast cell tumors was similar to that in healthy laboratory dogs. In summary, toceranib phosphate exhibited moderate clearance, a high volume of distribution, and a moderate elimination half-life. After a single oral dose at 3.25 mg/kg, the concentration vs. time curve showed broad, sustained exposure with measurable concentrations for more than 48 h. These pharmacokinetic parameters support every-other-day administration of toceranib phosphate at an initial dose of 3.25 mg/kg for the treatment of mast cell tumors in dogs.