Maximum first pass metaboilsm is seen by which route ?
Ans. is 'd' i.e., Oral First pass metabolism is seen with oral and rectal routes. Maximum first pass metabolism is seen with oral route. In rectal route, drug absorbed into external hemorrhoidal veins bypasses liver, but not that absorbed into internal haemorrhoidal veins -First pass metabolism occurs, but less than oral route (avoids first pass metabolism to 50%). Most rapid onset of action is seen with I. route. Bioavailability by I. V route is 100%.
Intravenous
Interaaerial
Rectal
Oral