Apotil is effective following a single subcutaneous injection. The concentration of tilmicosin achieved in the lung is substantially higher than that in serum. In calves, the concentration of tilmicosin in the lung has been found to remain above the MIC90 for Mannheimia haemolytica for at least 72 hours following a single subcutaneous injection at the recommended dose.
Tilmicosin is eliminated from the udder without the need for milking. Injecting cows with tilmicosin at the beginning of the dry period resulted in an initial concentration of tilmicosin in dry-udder secretion of 8000 µg/ml. By day 11 of the dry period, it had decreased to 100 µg/ml. By day 30, tilmicosin was not detected in dry-udder secretions.