This occurs when a substance passes from the fluid in the tubular lumen through the apical membrane, across the cytosol , and then into the interstitial fluid.
Yes, it's potent stuff. Cat receive it either as an injection or orally. It takes effect in roughly half an hour, lasting about 8 hours before another administration is necessary. Cats usually react negatively to opiates, but buprenorphine is an exception. That's one reason vets use it if they can receive the necessary special certification.
com: Buprenorphine can be detected with drug tests for 7-10 days at typical doses, although this time could vary considerably with much higher or much lower doses along with the individual's metabolism rate.. Bupe has a long 1/2 life so don't expect it to clear quickly.