Evaluation of regional limb perfusion with erythromycin using the saphenous, cephalic, or palmar digital veins in standing horses

There are no reported studies evaluating the use of erythromycin for regional limb perfusion (RLP) in horses. Our hypothesis was that using the cephalic and saphenous veins forRLPwill enable delivery of therapeutic concentrations of erythromycin to the distal limb. Nineteen healthy horses participated in the study. The cephalic, saphenous or palmar digital (PD) vein was used to perfuse the limb with erythromycin. Synovial samples were collected from the metacarpo/metatarso‐phalangeal (MCP/MTP) joint and blood samples were collected from the jugular vein. Maximum concentration (Cmax) of erythromycin in theMCPjoint using the cephalic vein was 113 mg/L. TheCmaxof erythromycin in theMTPjoint using the saphenous vein was 38 mg/L. Erythromycin administered using thePDvein was not detectable in theMCP/MTPjoint of four of six horses. Concentrations of erythromycin achieved in the synovial fluid of theMCP/MTPjoint were between 152 and 452 times the minimal inhibitory concentration (MIC) forRhodococcus equi(R. equi). In conclusion, the results indicate that when using the saphenous or cephalic veins forRLP, therapeutic concentrations of erythromycin in theMTP/MTPjoint can be consistently reached.