Model-Informed Drug Development for Antimicrobials: Translational PK and PK/PD Modeling to Predict an Efficacious Human Dose for Apramycin.

Apramycin represents a subclass of aminoglycoside antibiotics that has been shown to evade almost all mechanisms of clinically relevant aminoglycoside resistance. Model-informed drug development may facilitate its transition from preclinical to clinical phase. This study explored the potential of pharmacokinetic/pharmacodynamic (PK/PD) modeling to maximize the use of in vitro time-kill and in vivo preclinical data for prediction of a human efficacious dose (HED) for apramycin. PK model parameters of apramycin from four different species (mouse, rat, guinea pig, and dog) were allometrically scaled to humans. A semimechanistic PK/PD model was developed from the rich in vitro data on four Escherichia coli strains and subsequently the sparse in vivo efficacy data on the same strains were integrated. An efficacious human dose was predicted from the PK/PD model and compared with the classical PK/PD index methodology and the aminoglycoside dose similarity. One-compartment models described the PK data and human values for clearance and volume of distribution were predicted to 7.07 L/hour and 26.8 L, respectively. The required fAUC/MIC (area under the unbound drug concentration-time curve over MIC ratio) targets for stasis and 1-log kill in the thigh model were 34.5 and 76.2, respectively. The developed PK/PD model predicted the efficacy data well with strain-specific differences in susceptibility, maximum bacterial load, and resistance development. All three dose prediction approaches supported an apramycin daily dose of 30 mg/kg for a typical adult patient. The results indicate that the mechanistic PK/PD modeling approach can be suitable for HED prediction and serves to efficiently integrate all available efficacy data with potential to improve predictive capacity.

Pharmacokinetics and relative bioavailability of an oral amoxicillin-apramycin combination in pigs.

A new compound granular premix of amoxicillin (20% w/w dry mass)/apramycin (5% w/w dry mass) was developed, and its pharmacokinetics and relative bioavailability were determined in pigs following oral administration following a cross-over study design. The pharmacokinetic parameters of amoxicillin (t1/2λ = 6.43 ± 4.85h, Cmax = 3.2 ± 1.35 µg·mL-1, Tmax = 1.92 ± 0.58, AUCINF = 8.98 ± 2.11 h·µg·mL-1) and apramycin (t1/2λ = 8.67±4.4h, Cmax = 0.23 ± 0.12 µg·mL-1, Tmax = 2.25 ± 0.82 h, AUCINF = 12.37 ± 8.64h·µg·mL-1) when administered as the amoxicillin-apramycin granular premix did not significantly differ from those for the single-ingredient powder form of each component. The relative bioavailability of amoxicillin following oral administration of the amoxicillin-apramycin granular premix was 22.62% when compared to the intramuscular administration of commercial amoxicillin sodium-powder. This is the first report of a new amoxicillin-apramycin combination which has a potential veterinary application the for prevention and treatment digestive tract infections in pigs.

Correlation between apramycin and gentamicin use in pigs and an increasing reservoir of gentamicin-resistant Escherichia coli.

OBJECTIVES: Resistance towards the veterinary drug apramycin can be caused by the aac(3)-IV gene, which also confers resistance towards the important human antibiotic gentamicin. The objectives of this study were to investigate the temporal occurrence and the genetic background of apramycin and gentamicin resistance in Escherichia coli strains from pork, healthy pigs and diagnostic submissions from pigs and to investigate potential relationships to the use of apramycin and gentamicin at farm and national levels. METHODS: Data on Danish E. coli isolates from healthy pigs (indicator bacteria), diagnostic submissions from pigs (clinical isolates) and pork were obtained from the national surveillance of antimicrobial resistance and from routine diagnostic laboratories. Antimicrobial consumption data were obtained from the Danish Medicines Agency (1997-2000) and from the VetStat database (2001-2004). The genetic background for gentamicin resistance was investigated by PCR. Relationships between antimicrobial usage and resistance were analysed by chi2 test and logistic regression. RESULTS: At the farm level, the occurrence of apramycin/gentamicin cross-resistance was correlated to the use of apramycin (P < 0.001). At the national level, occurrence of apramycin/gentamicin cross-resistance in clinical E. coli O149 isolates was significantly correlated with the amounts and duration of apramycin use. The aac(3)-IV gene was detected in all tested cross-resistant isolates. CONCLUSIONS: Apramycin consumption at farm level is most probably driving the increasing occurrence of apramycin/gentamicin cross-resistant [aac(3)-IV positive] E. coli in diseased pigs and healthy finishers at slaughter. The duration of use and amounts used both had a significant effect on the prevalence of apramycin/gentamicin cross-resistance in diseased weaning pigs at the national level.

Susceptibility of Escherichia coli from growing piglets receiving antimicrobial feed additives.

Concerns regarding an apparent association between the use of antimicrobial feed additives (AFAs) in food animal production and a concomitant increase in antimicrobial drug resistance among zoonotic enteropathogens have provided the impetus to propose cessation of their use. While AFAs have been used in food animal production for nearly 50 years, the future use of AFAs will require an understanding of the effects of different classes of antimicrobials on the antimicrobial resistance of commensal flora. The present study examines the effect of three AFAs (apramycin, carbadox, and chlortetracycline) on the antimicrobial susceptibility of Escherichia coli in growing piglets and on animal performance. Three replicate trials were conducted using growing piglets fed standard diets with and without antimicrobial feed additives (AFAs). Fecal samples were cultured selectively for E. coli at regular intervals from all piglets from birth to market and antimicrobial susceptibility testing of E. coli isolates was performed using a replica-plate screening method and a broth microdilution method. While resistance to tetracycline in E. coli varied widely by sample, group, and trial, a significant increase in the percentage of resistant isolates was observed in piglets receiving AFAs when compared to controls (p < 0.0001). Resistance to apramycin increased in E. coli from piglets fed apramycin when compared to controls (p < 0.0001). However, upon removal of apramycin, resistance in E. coli declined to baseline levels by day 75. Piglets receiving AFAs demonstrated improved feed efficiency during phase 4 (p < 0.001), and higher average daily gains in phases 3 and 4 (p < 0.0001). This study suggests that antimicrobial resistance to AFAs in E. coli is drug-dependent and that some antimicrobials may be suitable for continued use in feeds during specified growth periods without concern for persistence of resistant E. coli populations.

Effects of antibiotic regimens on the fecal shedding patterns of pigs infected with salmonella typhimurium.

An experiment was conducted to determine (i) the effects of antibiotic regimens on the shedding patterns of pigs infected with Salmonella Typhimurium and (ii) whether antibiotic resistance increases the incidence of pathogen shedding. The experiment involved 48 50-day-old pigs challenged with Salmonella Typhimurium and receiving one of four antibiotic regimens including (i) intramuscular injection of ceftiofur sodium followed by inclusion of oxytetracycline in the feed; (ii) apramycin in the feed for 14 days followed by oxytetracycline; (iii) carbadox in the feed until pigs reached 35 kg followed by oxytetracycline; (iv) no antibiotics (control). Fecal samples were collected preinoculation, 2 and 4 days postinoculation (DPI) and at weekly and biweekly intervals thereafter to determine shedding patterns. Salmonella Typhimurium isolates from 2, 4, 7, 21, 42, and 70 DPI were analyzed for antibiotic resistance. A time effect (P < 0.05) was observed, indicating that the proportion of isolates resistant to at least one antibiotic varied over time. Overall resistance was determined to be 46% at 2 DPI and increased significantly (P < .05) thereafter. Treatment x time and antibiotic x time interactions were also observed (P < 0.05) as the percentage of isolates resistant to each test antibiotic increased over time. In no case did the development of antibiotic resistance result in an increased incidence of shedding of the original inoculate. The incidence of shedding was reduced in pigs receiving the apramycin-oxytetracycline treatment, when compared to control pigs; however, no differences were observed between antibiotic treatments.

Kinetic disposition, systemic bioavailability and tissue distribution of apramycin in broiler chickens.

Apramycin was administered to chickens orally, intramuscularly and intravenously to determine blood concentration, kinetic behaviour, bioavailability and tissue residues. Single doses of apramycin at the rate of 75 mg kg-1 body weight were given to broiler chickens by intracrop, i.m. and i.v. routes. The highest serum concentrations of apramycin were reached 0.20 and 0.76 hours after the oral and i.m. doses with an absorption half-life (t1/2(ab.)) of 0.10 and 0.19 hours and an elimination half life (t1/2(beta)) of 1.22 and 2.31 hours respectively. The systemic bioavailability was 2.0 and 58 per cent after intracrop and i.m. administration, respectively, indicating poor absorption of the drug when given orally. Following i.v. injection, the kinetics of apramycin was described by a two-compartment open model with a (t1/2(alpha)) of 1.5 hours, (t1/2(beta)) of 2.1 hours. Vd(ss) (volume of distribution) of 4.82 litre kg-1 and C1(B) (total body clearance) of 1.88 litre kg-1 hour-1. The serum protein-binding of apramycin was 26 per cent. The highest tissue concentrations of apramycin were present in the kidneys and liver. No apramycin residues were detected in tissues after six hours except in the liver and kidneys following intracrop dosing and kidneys following i.m. administration.

[Apramycin blood concentrations and distribution in the body of calves after different methods of administration]. / Kruvni kontsentratsii i razpredelenie na apramitsina v organizma na teleta sled razlichni nachini na prilagane.

The serum concentrations of apramycin in calves were studied after i/v application at the rate of 20 mg/kg body mass, after i/m injection at 20-40 mg/kg b. m., and after oral administration (with milk) at 40 mg/kg b. m. in terms of establishing certain pharmacokinetic parameters. It was found that at i/v route of application the concentrations of the antibiotic ranged above 2 micrograms/cm3 within the interval from the 15th min up to the 8h hour. The time of half-distribution (t1/2 alpha) was 0.28 h, while the biologic half-life of half-elimination (t1/2 beta) was 2.31 h. After muscular application of apramycin at 20 and 40 mg/kg it was rapidly adsorbed at the site of injection; the maximum concentrations were 99 micrograms/cm3 and 202 micrograms/cm3, resp., from the first to the second hour. Levels above 2 micrograms/cm3 were found in the blood serum in the course of 8 to 10 hours when the antibiotic was applied at 20 mg/kg b. m., and they have persisted for more than 12 hours when it was administered at the rate of 40 mg/kg. The biologic half-life (t1/2 beta) was 1.63 h and 1.97 h, respectively. Following the oral administration of the antibiotic at 40 mg/kg subtherapeutic levels were established up to the 24 th hour, with the exception of the interval of the 6 th to 8 th when the concentrations were below the minimum therapeutic one (2 micrograms/cm3).(ABSTRACT TRUNCATED AT 250 WORDS)

Apramycin: minimal inhibitory concentrations for avian Escherichia coli and serum levels after intramuscular injection in turkeys.

The minimal inhibitory concentrations (MIC) of apramycin, a unique aminocyclitol antibiotic, for 100 Escherichia coli isolates recovered from clinical cases of avian colibacillosis were determined using the agar dilution method. All isolates were inhibited at apramycin concentration of 8.0 micrograms/ml; 90 and 50% of the isolates were inhibited at 6.6 and 3.4 micrograms/ml, respectively. A commercial injectable product containing 200 mg apramycin/ml was administered intramuscularly (i.m.) to groups of 6- and 12-week-old turkeys at 10, 15 and 20 mg/kg. Apramycin was quickly absorbed from the i.m. injection site. Mean peak serum drug concentrations were reached 1 h after treatment and were 19.5, 27.5 and 36.0 micrograms/ml, respectively. The serum elimination half-life (t 1/2) of the drug ranged between 1.75 h for the 10 mg/kg dose and 2.5 h for the 20 mg/kg dose. Very low concentrations of the drug were found 24 h after treatment. Duration of serum apramycin concentrations in relation to the MIC, dose, and age of birds was determined.

Clinical pharmacology of apramycin in calves.

The minimal inhibitory concentrations (MIC) of apramycin, a unique aminocyclitol antibiotic, were compared with the MIC of dihydrostreptomycin and neomycin for 323 Salmonella, 178 Escherichia coli and twenty-six Pasteurella multocida isolates recovered from newborn calves. Apramycin exhibited better in vitro anti-bacterial activity than dihydrostreptomycin and neomycin; isolates of Salmonella group B and E. coli resistant to the latter were sensitive to apramycin. The two-compartment open model was appropriate for the analysis of serum apramycin concentrations measured after intravenous (i.v.) administration. The distribution half-life (t 1/2 alpha) of the drug was 28 min, the elimination half-life (t 1/2 beta) was 4.4 h, and the apparent volume of distribution (V1) and the distribution volume at steady state (Vdss) were 0.34 and 0.71 l/kg, respectively. The drug was quickly and completely absorbed after intramuscular (i.m.) injection; peak serum drug concentrations were directly related to the dose administered, they were obtained 1-2 h after treatment and the i.m. t 1/2 beta was 5 h. There was no evidence of drug accumulation in the serum after three daily i.m. injections at 20 mg/kg. More than 95% of the i.v. and i.m. doses were recovered in the urine within 96 h post-treatment but the cumulative percentage of drug recovery in the urine after oral treatment was 11%. The durations of free drug concentrations in the tissues after i.v. and i.m. injection were estimated from the serum drug level data, percent of serum protein binding, Vdss, t 1/2 beta, and the MIC. Computations showed that apramycin should be administered i.m. at 20 mg/kg every 24 h in order to maintain in tissues potentially effective drug concentrations sufficient to inhibit 50% of the Salmonella, E. coli, and P. multocida isolates, and at 12-h intervals to inhibit 90% of the isolates.

[A comparison of the effectiveness of furazolidone and apramycin in the control of colibacillosis in weaned piglets]. / Een vergelijking van de effectiviteit van furazolidon en apramycine tegen colibacillose bij gespeende biggen.

To compare the effectiveness of furazolidone and apramycin (Apralan) in the treatment of oedema disease in pigs, a trial was made on a commercial farm on which colibacillosis was a recurrent problem. Medicated feed containing 100 ppm of apramycin and 400 ppm of furazolidone respectively was given for three weeks after weaning. 112 Piglets were distributed over 10 battery houses at random. Results are summarized in Figure 1.