Each drug has pharmacokinetics that must be defined for the substance to be used in humans and animals. Currently, one of the basic analytical tools for pharmacokinetics studies is high-performance liquid chromatography coupled with mass spectrometry. For this analytical method to be fully reliable, it must be properly validated. Therefore, the aims of this study were to develop and validate a novel analytical method for 4-acetamidobenzoic acid, a component of the antiviral and immunostimulatory drug Inosine Pranobex, and to apply the method in the first pharmacokinetics study of 4-acetamidobenzoic acid in pigs after oral administration. Inosine Pranobex was administered under farm conditions to pigs via drinking water 2 h after morning feeding at doses of 20, 40, and 80 mg/kg. For sample preparation, we used liquid–liquid extraction with only one step—protein precipitation with 1 mL of acetonitrile. As an internal standard, we used deuterium labeled 4-acetamidobenzoic acid. The results indicate that the described method is replicable, linear (r² ≥ 0.99), precise (2.11% to 13.81%), accurate (89% to 98.57%), selective, and sensitive (limit of quantitation = 10 ng/mL). As sample preparation requires only one step, the method is simple, effective, cheap, and rapid. The results of the pilot pharmacokinetics study indicate that the compound is quickly eliminated (elimination half-life from 0.85 to 1.42 h) and rapidly absorbed (absorption half-life from 0.36 to 2.57 h), and that its absorption increases exponentially as the dose is increased.

Isoxazoline derivatives have rapidly become cornerstone ectoparasiticides in veterinary medicine, providing high efficacy and long-lasting protection against fleas, ticks, and other arthropods in companion animals and, more recently, in food-producing species. This review summarizes current knowledge on the chemistry, pharmacology, and toxicology of the main veterinary isoxazolines - fluralaner, afoxolaner, sarolaner, and lotilaner - with particular emphasis on safety profiles and broader One Health considerations. Chemically, these compounds are highly lipophilic, fluorinated molecules with distinctive stereochemistry; the selective use of biologically active S-enantiomers has improved potency while limiting off-target effects. Isoxazolines act through non-competitive antagonism of γ-aminobutyric acid (GABA) - and L-glutamate-gated chloride channels in arthropods, resulting in sustained neuronal hyperexcitation and parasite death, with markedly higher affinity for arthropod than mammalian receptors. Pharmacokinetically, the compounds exhibit variable oral bioavailability but share extensive plasma protein binding, large volumes of distribution, low clearance, and long elimination half-lives, which underlie their prolonged clinical efficacy but also raise concerns regarding tissue accumulation and delayed adverse effects. Controlled studies generally demonstrate wide safety margins; however, post-marketing pharmacovigilance has identified rare but sometimes serious neurological adverse events, particularly in predisposed animals or in the context of impaired efflux transport, such as ABCB1/MDR1 mutations or P-glycoprotein inhibition. The authorization of fluralaner for use in laying hens and evidence of residues in eggs approaching established maximum residue limits emphasize the importance of continued residue monitoring and refinement of withdrawal periods. Moreover, the environmental persistence of isoxazolines and their pronounced toxicity to non-target invertebrates highlight emerging ecotoxicological concerns. Collectively, veterinary isoxazolines represent a highly effective yet complex class of antiparasitic agents whose safe and sustainable use requires integrated pharmacological, toxicological, residue, and environmental risk assessment.

Background: Renal replacement therapy (RRT), widely used in the treatment of renal injury during sepsis, aims to eliminate the toxins and proinflammatory cytokines involved in the pathomechanism underlying septic shock. Dialysis filters are characterized by a high adsorption potential for cytokines in RRT in the case of septic renal injury. For the treatment of sepsis with antibiotics, it is of key importance to achieve the desired values of PK/PD indices. Continuous renal replacement therapy (CRRT) may affect antimicrobial clearance, increasing their elimination in some cases. Methods: The aim of this study was to determine the degree of adsorption for linezolid on three different types of filters used in CRRT. In our in vitro study, a continuous veno-venous hemofiltration (CVVH) was conducted using three types of filters: polysulfone (PS), polyethyleneimine-treated polyacrylonitrile (PAN PEI), and non-PEI-treated polyacrylonitrile (PAN). Each type of filter was used in three CVVH cycles, involving the use of 600 mg of linezolid dissolved in 700 mL of bovine blood or in 700 mL of 0.9% NaCl. In each case, the total volume of the obtained solution was 1000 mL. Blood samples were collected at particular time points to measure their drug concentration. The differences in mean drug/NaCl adsorption and drug/blood adsorption were determined using a one-way ANOVA with multiple comparisons via Tukey’s post hoc test; a p-value of <0.05 was considered significant. Results: A significant adsorption of linezolid was found for PAN PEI filters, both in samples obtained from bovine blood and 0.9% NaCl solutions, at the endpoint. In PAN PEI samples, the concentration of linezolid in 0.9% NaCl solutions decreased from 594.74 μg/mL to 310.66 μg/mL after 120 min (the difference was established at 52%). In blood samples, the initial concentration was 495.18 μg/mL, which then decreased to 359.84 μg/mL (73% of the beginning value). No significant adsorption was demonstrated on PAN or PS filters. Conclusion: There is a need for in vivo research to confirm the effect of filter type on linezolid concentration in patients undergoing CRRT.

Introduction: Isoxazoline derivatives such as fluralaner, sarolaner, lotilaner, and afoxolaner are a new class of insecticide and acaricide compounds. These compounds are characterised by rapid action and high efficacy over a period of up to several weeks. A method for identifying all four isoxazoline derivatives in animal and human plasma has not been proposed to date. Therefore, the aim of this study was to develop and validate a novel analytical method for the determination of fluralaner, sarolaner, lotilaner, and afoxolaner in laying hen plasma and to revalidate the proposed method in human, canine and feline plasma. Material and Methods: The plasma concentrations of isoxazoline derivatives were determined by ultra-high performance liquid chromatography–tandem mass spectrometry. Analytical samples were prepared by precipitating proteins with a mixture of 96% acetonitrile and 4% ammonium hydroxide (v/v). Chromatographic separation was achieved on a chromatographic column (1.8 μm 2.1 × 100 mm) using 0.1% formic acid in water and 0.1% formic acid in acetonitrile with gradient elution. Results: The results indicate that the described method is replicable, linear (r ² = 0.99), precise (1.66% to 14.97%), accurate (1.19% to 11.67%), selective and sensitive (limit of quantitation = 1 ng/mL). Depending on the studied compound and animal species, total recovery reached 85–99%, and the matrix effect did not exceed 15% in any of the analyses. Conclusion: The proposed method is simple, effective, inexpensive and rapid because it requires only a single-step sample preparation protocol.

Doxycycline (DOX) is one of the most used antibiotic in large-scale farming. However, its effect on Yellow mealworm remains unknown. Therefore, this study aimed to determine the bioavailability and systemic distribution of DOX after its inclusion in the diet of Tenebrio molitor larvae and to demonstrate whether this antibiotic affects the total protein content in the haemolymph and the biomass gain of the insects. Larvae were divided into a control group (C) and an experimental group (E) fed with DOX hyclate at 250 mg/kg for two weeks. DOX levels were measured in whole larvae and carcasses using UPLC-MS/MS at various time points from 0.25 to 14 days, while total haemolymph protein was determined on days 0, 2, 3, 7 and 14 using A280 protein measurements with spectrometer-based method. In group E, DOX concentrations in whole larvae were significantly higher ( ) compared to carcasses across the experiment. The total protein content in the haemolymph of larvae in group E was significantly lower on days 3, 7 ( ) and 14 ( ) compared to group C. There were no significant differences in the larval biomass between groups C and E. The obtained results indicate for the first time that DOX is partially absorbed (approximately 30%) from the digestive tract of T. molitor larvae and causes a significant reduction in the level of total protein in the haemolymph, although this change does not significantly affect the larval biomass. These results provide preliminary evidence that DOX can be distributed within T. molitor larvae.

Renal replacement therapy (RRT), widely used in the treatment of renal injury in the course of sepsis, aims to eliminate the toxins and proinflammatory cytokines, involved in the pathomechanism underlying septic shock. Dialysis filters characterised by a high adsorption potential for cytokines in RRT when septic renal injury is the case. It is of key importance in the antibiotics treatment of sepsis to achieve desired values of PK/PD indices. Continuous renal replacement therapy (CRRT) may affect antimicrobial clearance, increasing their elimination in some cases. The aim of this study was to determine the degree of adsorption for linezolid, on three different types of filters used in CRRT. In our in vitro study a continuous veno-venous hemofiltration (CVVH) was conducted using 3 types of filters: polysulfone (PS), polyethyleneimine-treated polyacrylonitrile (PAN PEI) and non-PEI-treated polyacrylonitrile (PAN) filters. Each type of filter was used in 3 CVVH cycles, involving the use of 600 mg of linezolid dissolved in 700 ml of bovine blood or in 700 ml of 0.9% NaCl. In each case the total volume of the obtained solution was 1000 ml. Blood samples, at particular time points, were collected in order to measure drug concentration. The differences in mean drug/NaCl adsorption and drug/ blood adsorption were determined using one-way ANOVA with multiple comparisons by Tukey post-hoc test. A p-value of < 0.05 was considered to be significant. A significant adsorption of linezolid was found for PAN PEI filter, both in samples obtained from bovine blood and 0.9% NaCl solutions, at the endpoint. No significant adsorption was demonstrated on PAN or PS filters. There is a need for in vivo research to confirm the effect of filter type on linezolid concentration in patients undergoing CRRT.