Pharmacokinetics and lung and muscle concentrations of tulathromycin following subcutaneous administration in white‐tailed deer (Odocoileus virginianus)

Abstract

Respiratory tract infections are common in farmed North American white-tailed deer (Odocoileus virginianus). Tulathromycin is approved for use in cattle but not deer but is often employed to treat deer. The pharmacokinetic properties and lung and muscle concentrations of tulathromycin in white-tailed deer were investigated. Tulathromycin was administered to 10 deer, and then, serum, lung, and muscle tulathromycin concentrations were measured using liquid chromatography-mass spectrometry (LC-MS). The mean maximal serum tulathromycin concentration in deer was 359 ng/mL at 1.3 h postinjection. The mean area under the serum concentration-time curve, apparent volume of distribution, apparent clearance, and half-life was 4883 ng·h/mL, 208 L/kg, 0.5 L/h/kg, and 281 h (11.7 days), respectively. The maximal tulathromycin concentration in lung and muscle homogenate from a single animal was 4657 ng/g (14 days) and 2264 ng/g (7 days), respectively. The minimum concentrations in lung and muscle were 39.4 ng/g (56 days) and 9.1 ng/g (56 days), respectively. Based on similarity in maximal serum concentrations between deer and cattle and high lung concentrations in deer, we suggest the recommended cattle dosage is effective in deer. Tissue concentrations persisted for 56 days, suggesting a need for longer withdrawal times in deer than cattle. Further tissue distribution and depletion studies are necessary to understand tulathromycin persistence in deer tissue; clinical efficacy studies are needed to confirm the appropriate dosage regimen in deer.

Should Airway Interstitial Fluid Be Used to Evaluate the Pharmacokinetics of Macrolide Antibiotics for Dose Regimen Determination in Respiratory Infection?

“…The lungs may have a much higher macrolide concentration than the thigh. Others also reported that lung tissues contain higher macrolide concentrations than those of muscle [ 20 ], fat [ 21 ], and skin [ 22 ]. In addition, higher clarithromycin concentrations were found in pulmonary epithelial lining fluid (PELF) than the serum of mice [ 19 ].…”

“…Based on these results, they recommended “standard PK/PD concepts can be applied to determine a regimen for a macrolide”. However, the ISF of different tissues has different macrolide concentrations; lungs have higher concentrations than muscle, fat, and skin [ 20 , 21 , 22 ]. In addition, pulmonary ISF concentrations of a macrolide are much higher than those of plasma [ 38 ].…”