The pharmacokinetic behaviour of enrofloxacin (ENRO) in plasma and nasal secretions of healthy pigs was investigated, after a single-dose intramuscular administration of 2.5 mg/kg body weight of the drug. Blood samples and nasal secretions were collected at predetermined times after drug administration. Concentrations of ENRO and its active metabolite ciprofloxacin (CIPRO) were determined in plasma and nasal secretions by high-performance liquid chromatography (HPLC). CIPRO was not detected probably because we investigated young weaned pigs. The data collected in 12 pigs for ENRO were subjected to noncompartmental analysis. In plasma, the maximum concentration of drug (C(max)), the time at which this maximum concentration of drug (T(max)) was reached, the elimination half-life (t(1/2)(beta)) and the area under the concentration vs. time curve (AUC) were, respectively, 694.7 ng/mL, 1.0 h, 9.3 h and 8903.2 ngxh/mL. In nasal secretions, C(max), T(max), t(1/2)(beta) and AUC were, respectively, 871.4 ng/mL, 2.0 h, 12.5 h and 11 198.5 ngxh/mL. In a second experiment conducted in 10 piglets, the relationship between concentrations of ENRO measured in the plasma and the nasal secretions has been determined following single-dose intramuscular administration of 2.5, 10 or 20 mg/kg body weight of the drug. It has been demonstrated that, among several variables, i.e., (1) the dose administered, (2) the time between intramuscular injection and blood sampling, (3) the age, (4) the sex, (5) the animal body weight and (6) the plasma concentration of the drug, only the latter influenced significantly the ENRO concentration in nasal secretions. Practically, using a generalized linear mixed model, ENRO concentrations in the nasal secretions (microg/mL) can be predicted taking into account the ENRO concentrations in plasma (microg/mL), according to the following equation:

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The penetration of oxytetracycline (OTC) in plasma and nasal secretions of healthy pigs was evaluated during the first study, in response to oral dose of 20 mg of OTC per kg of body weight (bwt) per day as a 400 mg/kg feed medication (n = 5) and to intramuscular (i.m.)-administered formulations at 10 mg/kg bwt (n = 5), 20 mg/kg bwt (n = 5), 40 mg/kg bwt (n = 5). Concentrations of OTC in plasma and nasal secretions were determined by a validated ultra-high performance liquid chromatography associated to tandem mass spectrometry method (UPLC/MS/MS). The objectives were to select the efficacy treatment and to evaluate the possibility to predict nasal secretions concentrations from those determined in plasma. The animals were housed together in each experiment. In each group, the treatment was administered once daily during 6 consecutive days, and nasal secretions and plasma were collected after 4 and 24 h at day 2 and day 6. For oral administration, only one medicated feed was prepared and distributed to all the animals together and was consumed in approximately 1 h. To meet recommendations of efficacy for OTC in nasal secretions, only the i.m. of 40 mg/kg bwt associated to an inter-dosing interval of 24 h provides and maintains concentrations in nasal secretions ≥1 μg/mL, appropriate to the MIC 50 and 90 of Pasteurella multocida and Bordetella bronchiseptica, respectively, the main pathological strains in nasal secretions. It has been demonstrated that, using a generalized linear mixed model (GLMM), OTC in the nasal secretions (μg/mL) can be predicted taking into account the OTC concentrations in plasma (μg/mL), according to the following equation: OTC(nasal secretions)  = 0.28 OTC(plasma) -1.49. In a second study, the pharmacokinetic behaviour of OTC in plasma and nasal secretions of healthy pigs was investigated, after single-dose i.m. of 40 mg/kg bwt of the drug. Blood samples and nasal secretions were collected at predetermined times after drug administration. The data collected in 10 pigs for OTC were subjected to non-compartmental analysis. In plasma, the maximum concentration of drug (C(max) ), the time at which this maximum concentration of drug (T(max) ) was reached, the elimination half-life (t½) and the area under the concentration vs. time curve (AUC) were, respectively, 19.4 μg/mL, 4.0, 5.1 h and 150 μg·h/mL. In nasal secretions, C(max) , T(max) , t½ and AUC were, respectively, 6.29 μg/mL, 4.0, 6.6 h and 51.1 μg·h/mL.

A generic method was developed for the liquid chromatographic (LC) assay of six corticosteroids and salicylic acid in different dermatological formulations containing methylparaben and propylparaben or sorbic acid as preservatives. An adequate separation was obtained using octadecylsilica as stationary phase and a mixture of acetonitrile (MeCN) and 25 mM phosphate buffer of pH 3.5 as mobile phase. Segmented gradient elution was applied from 30 to 45% of MeCN in 9.9 minutes, then from 45 to 96% in 19.0 minutes. UV detection was performed at 240 nm. The method was validated. Very good results were obtained with respect to hnearity, selectivity, precision and accuracy. the chromatographic methods, the LC methods, which are certainly the most commonly used, are mainly based on isocratic elution. Very few LC methods were developed using linear gradient elution [26,33].The aim of this paper is to describe the development of a simple and rapid generic method for the LC determination of the six CTs and SA in different pharmaceutical forms such as gels, lotions and creams. Afterwards, the method is validated and its applicability to the quantitative assay of the six CTs and SA in the gels, the lotions and the creams is tested.