Draxxin 25: Product Information (Page 2 of 4)

Swine

Following intramuscular (IM) administration to feeder pigs at a dosage of 2.5 mg/kg BW, tulathromycin is nearly completely absorbed, with peak plasma concentrations achieved within ~0.25 hr. The volume of distribution exceeds 15 L/kg, which is consistent with extensive tissue binding. This large distribution volume results in a long terminal elimination half- life (60 to 90 hours) despite a rapid systemic free drug clearance (187 mL/kg/hr). There are no gender differences in swine tulathromycin pharmacokinetics.

Comparative Bioavailability Summary

Despite slightly lower peak concentrations with DRAXXIN 25 Injectable Solution, a single IM dose of 2.5 mg tulathromycin/kg BW of either DRAXXIN Injectable Solution (100 mg/mL) or DRAXXIN 25 Injectable Solution (25 mg/mL) resulted in comparable tulathromycin total systemic exposure. Therefore, DRAXXIN 25 Injectable Solution is considered to be therapeutically equivalent to DRAXXIN Injectable Solution when administered to swine by IM injection at a dose of 2.5 mg tulathromycin/kg BW.

Calves

Following subcutaneous (SC) administration into the neck of feeder calves at a dosage of 2.5 mg/kg BW, tulathromycin is nearly completely absorbed, with peak plasma concentrations achieved within ~0.25 hr. The volume of distribution exceeds 11 L/kg4, which is consistent with extensive tissue binding. This large distribution volume results in a long terminal elimination half- life of more than 100 hours, despite a rapid systemic free drug clearance (170 mL/kg/hr). No pharmacokinetic differences are observed in castrated male versus female calves.

Comparative Bioavailability Summary

Despite lower peak concentrations with DRAXXIN 25 Injectable Solution, a single SC dose of 2.5 mg tulathromycin/kg BW of either DRAXXIN Injectable Solution (100 mg/mL) or DRAXXIN 25 Injectable Solution (25 mg/mL) resulted in comparable total systemic tulathromycin exposure. Therefore, DRAXXIN 25 Injectable Solution is considered to be therapeutically equivalent to DRAXXIN Injectable Solution when administered to calves by SC injection at a dose of 2.5 mg tulathromycin/kg BW.

4 Clearance and volume estimates are based on intersubject comparisons of 2.5 mg/kg BW administered by either subcutaneous or intravenous injection.

MICROBIOLOGY

Swine

Tulathromycin has demonstrated in vitro activity against A. pleuropneumoniae , P. multocida , B. bronchiseptica , H. parasuis , and M. hyopneumoniae. The MICs of tulathromycin against indicated pathogens collected from field studies were determined using methods recommended by the Clinical and Laboratory Standards Institute (CLSI, M31-A and M31-A3). MICs for H. parasuis were determined using Veterinary Fastidious Medium and were incubated up to 48 hours at 35 to 37°C in a CO2-enriched atmosphere. These values are represented in Table 3, below.

Table 3. Tulathromycin minimum inhibitory concentration (MIC) values * for indicated pathogens isolated from field studies evaluating SRD in the U.S. and Canada.
Indicated pathogen Date isolated No. of isolates MIC50 (μg/mL) MIC90 (μg/mL) MIC range (μg/mL)
*
The correlation between in vitro susceptibility data and clinical effectiveness is unknown.
The lowest MIC to encompass 50% and 90% of the most susceptible isolates, respectively.
Actinobacillus pleuropneumoniae 2000-20022007-2008 13588 1616 3216 16 to 324 to 32
Haemophilus parasuis 2000-2002 31 1 2 0.25 to > 64
Pasteurella multocida 2000-20022007-2008 5540 11 22 0.5 to > 64≤ 0.03 to 2
Bordetella bronchiseptica 2000-2002 42 4 8 2 to 8

*The correlation between in vitro susceptibility data and clinical effectiveness is unknown.

** The lowest MIC to encompass 50% and 90% of the most susceptible isolates, respectively

Calves

Tulathromycin has demonstrated in vitro activity against M. haemolytica , P. multocida , H. somni , and M. bovis , four pathogens associated with BRD. The MICs of tulathromycin against indicated pathogens collected from field studies using DRAXXIN Injectable Solution (100 mg/mL) were determined using methods recommended by the CLSI (M31-A2). These values are represented in Table 4, below.

Table 4. Tulathromycin minimum inhibitory concentration (MIC) values * for indicated pathogens isolated from field studies evaluating BRD in the U.S.
Indicated pathogen Date isolated No. of isolates MIC50 (μg/mL) MIC90 (μg/mL) MIC range (μg/mL)
Manneheimia haemolytica 1999 642 2 2 0.5 to 64
Pasteurella multocida 1999 221 0.5 1 0.25 to 64
Histophilus somni 1999 36 4 4 1 to 4
Mycoplasma bovis 1999 43 0.125 1

≤0.063 to > 64

* The correlation between in vitro susceptibility data and clinical effectiveness is unknown.

** The lowest MIC to encompass 50% and 90% of the most susceptible isolates, respectively.

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