Enteral administration is food ordrug administration via thehuman gastrointestinal tract. This contrasts withparenteral nutrition or drug administration (Greekpara, "besides" +enteros), which occurs from routes outside the GI tract, such asintravenous routes. Enteral administration involves the esophagus, stomach, and small and large intestines (i.e., the gastrointestinal tract). Methods of administration include oral, sublingual (dissolving the drug under the tongue), and rectal. Parenteral administration is via a peripheral or central vein.[1] Inpharmacology, the route of drug administration is important because it affectsdrug metabolism,drug clearance, and thusdosage. The term is fromGreekenteros 'intestine'.
Enteral administration may be divided into three different categories, depending on the entrance point into the GI tract: oral (bymouth), gastric (through thestomach), and rectal (from therectum). (Gastric introduction involves the use of a tube through the nasal passage (NG tube) or a tube in the belly leading directly to the stomach (PEG tube). Rectal administration usually involves rectalsuppositories.)
The mechanism for drug absorption from the intestine is for most drugs passive transfer, a few exceptions includelevodopa andfluorouracil, which are both absorbed throughcarrier-mediated transport. Forpassive transfer to occur, the drug has to diffuse through the lipidcell membrane of theepithelial cells lining the inside of the intestines. The rate at which this happens is largely determined by two factors:Ionization andlipid solubility.[2]
Factors influencing gastrointestinal absorption:
Drugs given by enteral administration may be subjected to significantfirst pass metabolism, and therefore, the amount of drug entering the systemic circulation following administration may vary significantly for different individuals and drugs. Rectal administration is not subject to extensive first pass metabolism.
-solution.jpg)
