Explanation: What is happening here is that the antibiotic is being actively transported into the proximal tubule during the process called tubular secretion.
Tubular secretion is when materials are transferred from peritubular capillaries to the renal tubular lumen. It is one of the many steps of the blood filtering process and the final goal is to secrete waste in form of urine.
In conclusion, the antibiotic is almost completely excreted, because it is actively transported into the proximal tubule during tubular secretion.
