In pharmacology, Enteral (Greek, enteros , meaning :intestine") is any route of drug administration that involves absorption of the drug through the gastrointestinal tract. This contrasts with the parenteral (Greek para: "besides" + enteros), meaning outside the intestines, or more specifically in pharmacology: Methods of introducing drugs or substances into the body other than through the gastrointestinal tract, via, for example, intravenous injection.
Forms of enteral administration 
Enteral administration may be divided into three different categories, oral, gastric, and rectal. (Gastric introduction involves the use of a tube through the nasal passage or a tube in the belly leading directly to the stomach.)
Drug absorption from the intestine 
The mechanism for drug absorption from the intestine is for most drugs passive transfer, a few exceptions include levodopa and fluorouracil, which are both absorbed through carrier-mediated transport. For passive transfer to occur, the drug has to diffuse through the lipid cell membrane of the epithelial cells lining the inside of the intestines. The rate at which this happens is largely determined by two factors: Ionization and lipid solubility.
Factors influencing gastrointestinal absorption:
First pass metabolism 
Drugs given by enteral administration may be subjected to significant first 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.
See also 
Wed, 01 May 2013 07:44:21 -0700
As of Wednesday, May 1, 2013, we have a detainee population of 166, and we currently have 100 detainees tracked as hunger strikers, with 23 receiving enteral feeds (feeding tubes). Four detainees receiving enteral feeds are being observed in the ...
Thu, 23 May 2013 06:24:26 -0700
“Children are dying,” says Steve Plogsted, a clinical pharmacist who chairs the drug-shortage task force of the American Society for Parenteral and Enteral Nutrition (ASPEN). “They're not getting any calcium or any zinc. Or they're not getting any ...
Mon, 20 May 2013 16:01:13 -0700
PHILADELPHIA -- Early parenteral nutrition in critically ill adults who could not tolerate early enteral nutrition did not lead to better survival outcomes or a shorter stay in the intensive care unit when compared with standard care, researchers found.
Mon, 20 May 2013 11:06:21 -0700
The early (within 24 hours of intensive care unit [ICU] admission) provision of intravenous nutrition among critically ill patients with contraindications (a condition that makes a particular procedure potentially inadvisable) to early use of enteral ...
Tue, 21 May 2013 18:07:52 -0700
As of Tuesday morning, according to a Gitmo spokesman, 103 of Guantanamo's 166 detainees were recognized as hunger strikers, with 30 being force-fed, or "receiving enteral feeds" in the language of the military. President Barack Obama has said he will ...
Tue, 21 May 2013 02:34:44 -0700
Breasseale declined to comment on the Twitter campaign, but confirmed that 30 of the Guantanamo hunger strikers have been force-fed via an enteral feed. Stafford Smith said that Aamer is not one of them. It's unclear how many people have called the ...
Sat, 18 May 2013 12:41:22 -0700
“If detainee continues to hunger strike and clinical criteria for the initiation of enteral feeding are met …the detainee may be admitted to the Detention Hospital or designated feeding block if medically stable. Authorisation is obtained via chain-of ...
Sat, 11 May 2013 14:41:32 -0700
Twenty-four hunger strikers are now receiving enteral feeds, with three people "being observed in the detainee hospital," according to Guantanamo Bay Public Affairs Director Lieutenant Colonel Samuel E. House. His most recent report put the official ...
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