Eight horses underwent IVRLP at two occasions through a 23-gauge 2cm long butterfly catheter. Regional anaesthesia of the ulnar, median and medial cutaneous antebrachial nerves was performed prior, and an 8cm rubber tourniquet was placed on the proximal radius for 30minutes following the infusion. The first infusion consisted of 2g of amikacin sulphate and 10mg of dexamethasone phosphate diluted with 0.9% NaCl to a total volume of 100ml. The second perfusion was performed after a 2-week washout period, the same protocol was used but without dexamethasone phosphate. Synovial fluid samples were collected from the metacarpophalangeal joint at T=0, 0.5, 2, 12, 24 and 36h post-infusion. Synovial fluid amikacin sulphate concentrations were determined by use of liquid chromatography/tandem mass-spectrometry. All horses (n=8) remained healthy throughout the study, and no adverse effects associated with the study were encountered. No statistically significant differences were found in synovial fluid amikacin sulphate concentrations between the treatment and the control group at any of the time points. In conclusion, dexamethasone phosphate can be used in IVRLP concomitantly with amikacin sulphate in cases of distal limb inflammation and pain without decreasing the synovial fluid concentration of amikacin sulphate.