The pharmacokinetic behaviours of amoxicillin (AMX) and clavulanic acid (CA) in swine were studied after either an intravenous or oral administration of AMX (10 mg/kg) and CA (2.5 mg/kg). The concentrations of these two medicines in swine plasma were determined using high‐performance liquid chromatographic‐tandem mass spectrometry, and the data were analysed using a noncompartmental model with the WinNonlin software. After intravenous administration, both substances were absorbed rapidly and reached their effective therapeutic concentration quickly. CA was eliminated more slowly compared with AMX. Moreover, the distribution volume of AMX was larger than that of CA, suggesting that AMX could penetrate tissues better. After oral administration of the granular formulation, no significant difference was observed in the mean elimination half‐life value between AMX and CA. The mean maximal plasma concentrations of AMX and CA, reached after 1.14 and 1.32 hr, were 2.58 and 1.91 μg/m, respectively. The mean oral bioavailability of AMX and CA was 23.6% and 26.4%, respectively. After oral administration, the T>MIC50 for three common respiratory pathogens was over 6.12 hr. Therefore, oral administration could be more effective in the clinical therapy of pigs, especially when administered twice daily.

Protocatechuic acid (PCA) is an antiviral agent against Avian Influenza virus (AIV) and Infectious Bursal Disease (IBD) virus, but its antiviral mechanism is unknown. In this study, we evaluated the humoral and cellular responses to PCA in specific pathogen-free (SPF) chickens. One hundred forty 35-day-old SPF chickens were randomly divided into 7 groups. The birds were inoculated with the commercial, attenuated Newcastle Disease Virus (NDV) vaccine and then received orally with 10, 20 or 40 mg/kg body weight of PCA for 30 days. Immune organ indexes, anti-Newcastle Disease Virus (NDV) antibodies and lymphocyte proliferation, but not body weight, were significantly increased in chicken treated with 40 mg/kg PCA, compared to the control birds treated with Astragalus polysaccharide (ASP). Survival rate was 70% and 60%, respectively, in the chickens with 40 mg/kg PCA, 20 mg/kg PCA while 50% survival was found in the birds treated with 125 mg/kg ASP. PCA treatment resulted in significantly lower viral load and reduced shedding. These results indicate that PCA may improve poultry health by enhancing both the humoral and cellular immune response.

Altrenogest, a synthetic progestogen, is characterized by its estrus synchronization in mares, ewes, sows, and gilts. To investigate the pharmacokinetic profile and evaluate its accumulation in gilts, 18 oral doses of 20 mg altrenogest/gilt/day were given to eight healthy gilts at an interval of 24 hr. Plasma samples were collected, and altrenogest was determined by ultra‐high‐performance liquid chromatography with mass spectrometry. WinNonlin 6.4 software was used to calculate the pharmacokinetic parameters through noncompartmental model analysis. After the first administration (D 1), the pharmacokinetic parameters, including Tmax, Cmax, and the elimination half‐life (T1/2λz), were similar to those observed after the final administration (D 18). However, the mean residence time at D 1 was significantly lower than D 18. As a whole, the mean steady‐state plasma concentration (Css), degree fluctuation (DF), accumulation factor (Rac), and area under the plasma concentration–time curve in steady state (AUCss) were 22.69 ± 6.15 ng/ml, 270.64 ± 42.51%, 1.53 ± 0.23, and 544.63 ± 147.49 ng hr/ml, respectively. These results showed that after 18 consecutive days of oral administration of altrenogest, plasma concentrations of altrenogest had a certain degree of fluctuation, without significant accumulations.

The pharmacokinetic properties of three formulations of vitacoxib were investigated in horses. To describe plasma concentrations and characterize the pharmacokinetics, 6 healthy adult Chinese Mongolian horses were administered a single dose of 0.1 mg/kg bodyweight intravenous (i.v.), oral paste, or oral tablet vitacoxib in a 3‐way, randomized, parallel design. Blood samples were collected prior to and at various times up to 72 hr postadministration. Plasma vitacoxib concentrations were quantified using UPLC‐MS/MS, and pharmacokinetic parameters were calculated using noncompartmental analysis. No complications resulting from the vitacoxib administration were noted on subsequent administrations, and all procedures were tolerated well by the horses throughout the study. The elimination half‐life (T1/2λz) was 4.24 ± 1.98 hr (i.v.), 8.77 ± 0.91 hr (oral paste), and 8.12 ± 4.24 hr (oral tablet), respectively. Maximum plasma concentration (Cmax) was 28.61 ± 9.29 ng/ml (oral paste) and 19.64 ± 9.26 ng/ml (oral tablet), respectively. Area under the concentration‐versus‐time curve (AUClast) was 336 ± 229 ng hr/ml (i.v.), 221 ± 94 ng hr/ml (oral paste), and 203 ± 139 ng hr/ml, respectively. The results showed statistically significant differences between the 2 oral vitacoxib groups in Tmax value. T1/2λz (hr), AUClast (ng hr/ml), and MRT (hr) were significantly different between i.v. and oral groups. The longer half‐life observed following oral administration was consistent with the flip‐flop phenomenon.