Abstract
The study objective was to determine the disposition of gamithromycin in plasma, peripheral blood polymorphonuclear cells (PMNs), pulmonary epithelial lining fluid (PELF), and bronchoalveolar lavage (BAL) cells in alpacas. A single subcutaneous injection of gamithromycin (6.6 mg/kg) was administered to six healthy adult alpacas. At various time points after administration, gamithromycin concentrations were analyzed via LC-MS/MS in plasma, PMNs, PELF, and BAL cells until Day 14 post-injection. Plasma gamithromycin concentrations were measured in all six alpacas; the remaining three body compartments were analyzed in four alpacas. Gamithromycin rapidly concentrated in blood PMNs, BAL cells, and PELF. Shorter T-max, and lower C-max,C- and AUC were observed in plasma than in the other three compartments. C-max was highest in BAL cells (26001.80 +/- 12400.00 ng/ml) and PMNs (2573.00 +/- 963.30 ng/ml) compared to PELF (660.80 +/- 413.70 ng/ml) and plasma (452.30 +/- 196.20 ng/ml). Mean terminal half-lives were 72.60 +/- 14.10 h in plasma, 56.60 +/- 10.60 h in PELF, 62.80 +/- 85.30 h in PMNs, and 93.60 +/- 124.80 h in BAL cells. No injection site reactions occurred. One alpaca developed colic but no other adverse reactions were noted. Overall, gamithromycin was highly concentrated in white blood cells and pulmonary fluids/cells. Clinical utilization of gamithromycin in alpacas should be done with caution until further investigation of potential for colic.