Aditoprim Research Articles

A physiologically based pharmacokinetic/pharmacodynamic model to determine dosage regimens and withdrawal intervals of aditoprim against Streptococcus suis.

Introduction: Streptococcus suis (S. suis) is a zoonotic pathogen threatening public health. Aditoprim (ADP), a novel veterinary medicine, exhibits an antibacterial effect against S. suis. In this study, a physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model was used to determine the dosage regimens of ADP against S. suis and withdrawal intervals. Methods: The PBPK model of ADP injection can predict drug concentrations in plasma, liver, kidney, muscle, and fat. A semi-mechanistic pharmacodynamic (PD) model, including susceptible subpopulation and resistant subpopulation, is successfully developed by a nonlinear mixed-effect model to evaluate antibacterial effects. An integrated PBPK/PD model is conducted to predict the time-course of bacterial count change and resistance development under different ADP dosages. Results: ADP injection, administrated at 20mg/kg with 12 intervals for 3 consecutive days, can exert an excellent antibacterial effect while avoiding resistance emergence. The withdrawal interval at the recommended dosage regimen is determined as 18days to ensure food safety. Discussion: This study suggests that the PBPK/PD model can be applied as an effective tool for the antibacterial effect and safety evaluation of novel veterinary drugs.

Dosing Regimen of Aditoprim and Sulfamethoxazole Combination for the Glaesserella parasuis Containing Resistance and Virulence Genes.

Glaesserella parasuis (G. parasuis) causes Glasser’s disease in pigs and causes high mortality in piglets. The new drug Aditoprim (ADP) alone or combined with Sulfamethoxazole (SMZ) is one of the good choices for treating respiratory infections. The objective of this study was to recommend the optimal dosing regimen for the treatment of G. parasuis infection which contains resistance and virulence genes by ADP/SMZ compound through pharmacokinetics–pharmacodynamics (PK-PD) modeling. The whole genome of the virulent strain G. parasuis H78 was obtained and annotated by whole genome sequencing. The results show that G. parasuis H78 consists of a unilateral circular chromosome with prophages in the genome. The annotation results of G. parasuis H78 showed that the genome contained a large number of virulence-related genes and drug resistance-related genes. The in vitro PD study showed that the antibacterial effect of ADP/SMZ compound against G. parasuis was time-dependent, and AUC/MIC was selected as the PK-PD modeling parameter. The PK study showed that the content of ADP/SMZ compound in pulmonary epithelial lining fluid (PELF) was higher than plasma, and there were no significant differences in ADP and SMZ PK parameters between the healthy and infected group. The dose equation to calculate the optimal dosing regimen of ADP/SMZ compound administration for control of G. parasuis infection was 5/25 mg/kg b.w., intramuscular injection once a day for 3~5 consecutive days. The results of this study provide novel therapeutic options for the treatment of G. parasuis infection to decrease the prevalence and disease burden caused by G. parasuis.

Preparation of Aditoprim Injection against Streptococcus suis in Pigs and a Dose Regimen Based on Pharmacokinetic-Pharmacodynamic Modeling.

In order to effectively treat the infection of Streptococcus suis and reduce the emergence of drug-resistant bacteria, an aditoprim (ADP) injection was developed in this study. The pharmaceutical property investigation results demonstrated that ADP injection was a clear yellow liquid with 10 g ADP distributing in every 100 mL solution uniformly. Its pH value and drug content were around 6.20 and 99.35~100.40%, respectively. And quality assessment preliminarily indicated its reliable quality and stability. Additionally, the bronchoalveolar lavage fluid method was first applied to evaluate accurate ADP concentration at infection site in this study. Through pharmacodynamic assay, the MIC, MBC and MPC of ADP against Streptococcus suis CVCC 607 was 2 μg/mL, 4 μg/mL and 12.8 μg/mL, respectively. The bacteria growth inhibition curves showed that ADP was a concentration-dependent antibacterial drug, and the PK-PD model parameter of AUC/MIC was selected. The pharmacokinetic parameters of alveolar fluid evaluated by WinNonlin software revealed similar pharmacokinetic process of ADP in healthy pigs and infected pigs. Combined with pharmacokinetics-pharmacodynamics (PK-PD) modeling, the dosage regimen of 3~5 days with an interval of 12 h at 4.10 mg/kg or 5.91 mg/kg could be adopted to treat the infection of Streptococcus suis. Consequently, this ADP injection with a multi-dose protocol would be a promising antimicrobial product for efficient treatment of S. suis infection of pigs.

Rapid determination of 2,4-diaminopyrimidine residues through sample pretreatment using immunomagnetic bead purification along with HPLC–UV

To reduce matrix interference and realize simultaneous detection of multiple homologous compounds (trimethoprim (TMP), diaveridine (DVD), ormetoprim (OMP), baquiloprim (BQP), and aditoprim (ADP) in pig, cattle, chicken, and fish muscles), an immunomagnetic bead (IMB)-based sample purification pretreatment with HPLC–UV was developed. A broad-spectrum monoclonal antibody (mAb, named 14C6) was prepared and conjugated with carboxylic-acid-functionalized magnetic nanoparticles using the active ester method to obtain IMBs for sample purification. The extraction solvent was optimized based on the extraction efficiency. Good linearity was observed for all the five analytes (10–200 μg/kg) with the LOD and LOQ of 5 and 10 μg/kg, respectively. The mean recoveries ranged from 62.5% to 76.9%, while the coefficient of variation was <12.2%. The IMB method afforded greater sample purification and enrichment than those achieved with the SPE column-based conventional method. Hence, the IMB-based sample purification is a useful tool to determine 2,4-diaminopyrimidine residues in edible animal tissues.

Antibacterial activity of combined aditoprim and sulfamethoxazole against Escherichia coli from swine and a dose regimen based on pharmacokinetic-pharmacodynamic modeling.

The mortality of livestock caused by pathogenic Escherichia coli (E. coli) still accounts for a large proportion of deaths in large-scale production and reproduction, which causes devastating economic losses to the pig breeding industry. The aims of this study were to investigate the antibacterial activity of combined aditoprim (ADP) and sulfamethoxazole (SMZ) against clinical isolates of E.coli from pigs and to develop a pharmacokinetic-pharmacodynamic (PK-PD) model to formulate the optimal dose of ADP/SMZ for the treatment of pig colibacillosis. Blood and ileum fluid samples were collected at different times after single intramuscular injection of ADP/SMZ (5/25mg/kg b.w.) to healthy pigs and E.coli-infected pigs. Concentrations of ADP and SMZ in plasma and ileum fluid were analyzed by HPLC. The peak concentration (Cmax ) and the area under the concentration-time curve (AUC0-24h ) in ileum fluid of healthy pigs were 1.76±0.27µg/ml and 18.92±2.87µg·h/ml for ADP and 19.15±2.63µg/ml and 125.70±11.86µg·h/ml for SMZ, respectively. Cmax and AUC0-24h in ileum fluid of infected pigs were 1.88±0.13µg/ml and 15.12±0.75µg·h/ml for ADP and 19.71±3.68µg/ml and 133.92±17.14µg·h/ml for SMZ, respectively. The minimum inhibitory concentrations (MICs) of combined ADP and SMZ (ADP/SMZ) against 185 strains of E.coli from pigs were determined. The MIC50 and MIC90 of ADP/SMZ were 0.5/2.5 and 4/20µg/ml, respectively. The MIC of the selected pathogenic E.coli SHC28 was 0.5/2.5µg/ml in Mueller-Hinton broth and 0.25/1.25µg/ml in ileum fluid, respectively. In vitro, the mutant prevention concentration, the post-antibiotic effect, growth, and time-killing curves in vitro and ex vivo of ADP/SMZ against the isolate SHC28 were assayed for PD studies. The results showed that ADP/SMZ exhibited strong concentration-dependent antimicrobial activity against E.coli. After integrating the in vivo pharmacokinetic parameters of infected pigs and ex vivo PD data using the sigmoid Emax (Hill) equation, the AUC24h /MIC values in ileum fluid for bacteriostatic, bactericidal, and bacterial eradication were 18.84, 65.39, and 110.68h, respectively. In conclusion, a dosage of 3.45/17.25mg/kg ADP/SMZ by intramuscular injection daily for 3 consecutive days may be sufficient to treat swine colibacillosis due to E.coli with a MIC of 0.5/2.5µg/ml.

The antibacterial activities of aditoprim and its efficacy in the treatment of swine streptococcosis

Aditoprim (ADP) has potential use as an antimicrobial agent in animals. However, its pharmacodynamic properties have not been systematically studied yet. In this study, the in vitro antibacterial activities of ADP and its main metabolites were assayed, and the in vivo antibacterial efficacy of ADP for the treatment of swine streptococcosis was evaluated. It was shown that Salmonella and Streptococcus from swine, Escherichia coli and Salmonella from chickens, E. coli, Streptococcus, Mannheimia, Pasteurella from calves, Streptococcus and Mannheimia from sheep, and E. coli, Flavobacterium columnare, Acinetobacter baumannii and Yersinia ruckeri from fishes were highly susceptible to ADP. Haemophilus parasuis from swine, Staphylococcus aureus, Aeromonas punctate, Mycobacterium tuberculosis, Streptococcus agalactiae from fishes, and Klebsiella from calves and sheep showed moderate susceptibility to ADP, whereas E. coli, Actinobacillus pleuropneumonia, Pasteurella, S. aureus, Clostridium perfringens from swine, S. aureus, C. perfringens from chickens, and S. aureus from calves were resistant to ADP. The main metabolites of ADP showed equal activity to that of their parent compound, and the prevention and therapeutic dosages of ADP recommended for swine streptococcosis were 10 and 20~40 mg/kg b.w., respectively. This study firstly showed that ADP had strong antibacterial activity and had potential to be used as a single drug in the treatment of bacterial infectious diseases.

Safety assessment of aditoprim acute, subchronic toxicity and mutagenicity studies.

Aditoprim (ADP), a new developed dihydrofolate reductase (DHFR) inhibitor, has great potential in clinical veterinary medicine because of its greater pharmacokinetic properties than structural analogs. Preclinical toxicology studies were performed to assess the safety of ADP including an acute oral toxicity test, a subchronic toxicity test and five mutagenicity tests. In the acute oral toxicity test, ADP was administered singly by oral gavage to Wistar rats and Kunming mice. The LD50 calculated was 1400 mg kg(-1) body weight (BW) day(-1) in rats and 1130 mg kg(-1) BW day(-1) in mice. In a subchronic study, Wistar rats were administered ADP at dose levels of 0, 20, 100 and 1000 mg kg(-1) diet for 90 days. Significant decreases were observed on body weight and food efficiency in the high-dose group. Treatment-related changes in clinical serum biochemistry were found in the medium- and high-dose groups. Significant increases in the relative weights of livers and kidneys in females and testis in males in the 1000 mg kg(-1) diet, and significant decrease in relative weights of livers in males in the 100 mg kg(-1) diet were noted. Histopathological observations revealed that the 1000 mg kg(-1) ADP diet could induce lymphocytic infiltration and hepatocytic necrosis near the hepatic portal area. The genotoxicity of ADP was negative in tests, such as the bacterial reverse mutation assay, mice bone marrow erythrocyte micronucleus assay, in vitro chromosomal aberration test, in vitro cho/hgprt mammalian cell mutagenesis assay and mice testicle cells chromosome aberration. Based on the subchronic study, the no-observed-adverse-effect level for ADP was a 20 mg kg(-1) diet, which is about 1.44-1.53 mg kg(-1) BW day(-1) in rats.

Determination of aditoprim and its oxidative metabolites in plasma and microsomal incubation mixtures by high-performance liquid chromatography.

A high-performance liquid chromatographic method is presented for the determination of aditoprim (ADP) and its two oxidative metabolites in biological fluids including sheep plasma and the incubation medium of liver microsomes. The compounds were separated using a highly deactivated C18 column; the mobile phase consisted of an 0.05 M phosphate buffer (pH 6) and acetonitrile in a ratio of 90:10 (v/v). The eluate was quantified by ultraviolet detection at 230 nm. Calibration curves were linear from 0.25 to 5 micrograms/ml. The limit of detection was 0.05 microgram/ml. In an in vivo kinetic study in sheep, N-monodesmethyl-ADP and N-didesmethyl-ADP appeared to be equally important metabolites. In contrast, in in vitro metabolism studies using liver microsomes from different animal species including sheep, N-didesmethyl-ADP was formed predominantly.

Some pharmacokinetic data of aditoprim and trimethoprim in healthy and tick-borne fever infected dwarf goats.

Aditoprim (AP) is a new dihydrofolate reductase inhibitor, which is structurally related to trimethoprim (TMP). The pharmacokinetics of AP (10 mg/kg) and TMP (20 mg/kg) were assessed in healthy dwarf goats. Therapeutic efficacy against rickettsial infections was tested in tick-borne fever (TBF) infected goats. The animals were given TMP (n = 5) or AP (n = 5) by i.v. injection, and subsequently the drugs were administered orally (same groups, similar doses). Finally, both groups were infected with TBF and the i.v. experiment was repeated. Plasma concentration-time curves for both drugs followed first-order two-compartment decay. For TMP, mean t1/2 beta +/- SEM (h) was 0.84 +/- 0.06 (i.v. control) and 0.90 +/- 0.06 (i.v. infected), respectively, whereas for AP values of 8.00 +/- 0.31 (i.v. control) and 10.28 +/- 0.67 (i.v. infected) were obtained (P less than 0.05). Mean Vd beta +/- SEM values (l/kg) were 3.84 +/- 0.27 (i.v. control) and 4.07 +/- 0.85 (i.v. infected) for TMP (NS) and 7.02 +/- 0.63 vs 9.29 +/- 0.21 (P less than 0.05) for AP. After i.v. injection, rumen fluid concentrations of AP were significantly (P less than 0.05) higher and more persistent than those of TMP. For AP, the plasma and rumen fluid concentrations at 3 h were 1.20 +/- 0.06 micrograms/ml and 0.85 +/- 0.17 microgram/ml, respectively. After oral administration of TMP, Cmax in plasma was 0.12 +/- 0.01 microgram/ml and the maximum was reached after 1.2 +/- 0.16 h; systemic bioavailability (F) was 10.3% (relative to AUC i.v.). Oral treatment with AP resulted in a Cmax value of 0.21 +/- 0.02 microgram/ml with Tmax of 22.5 +/- 1.65 h and a F value of 71%. Based on WBC, serum ALP and rectal temperature responses, it was concluded that both TMP and AP were inactive against Ehrlichia phagocytophila.