Absorption of drugs after oral administration: modes of transport, initial passage effects and enteroheptic cycle
Guenzet, J.; Agossou, M.; Bourin, M.
Il Farmaco; Edizione Pratica 40(11): 355-382
1985
ISSN/ISBN: 0430-0912 PMID: 4076412 Document Number: 265613
After oral administration, drugs pass across digestive membranes. This transfer occurs by passive diffusion (in most cases), by pinocytosis (for biological molecules), by active transport, by passing across aqueous pores. Only a part of the administered dose is absorbed because of biotransformations (gut flora and secretions). The absorbed molecule reacts with blood and hepatic enzymes. So, we have biotransformations at different levels (liver and lungs). First pass effect and enterohepatic cycle of drugs are examined. Pharmacokinetics are complicated by all the first pass effects (mucosal, luminal, hepatic and pulmonary): the complexity of plasma level kinetics after dosing is difficult to interpret.