In pharmacology, Enteral (Greek, enteros : Intestine) is a term used to describe routes of drug administration that involve absorption of the drug through the gastrointestinal tract. The term may also be used to describe something as residing in the gastrointestinal tract. This is contrasted with the term parenteral (Greek para: Besides + enteros: Intestine), 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[link]

Enteral administration may be divided into two different categories, oral and rectal.

Drug absorption from the intestine[link]

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.^[1]

Factors influencing gastrointestinal absorption:

• Gastrointestinal motility.
• Splanchnic blood flow.
• Particle size and formulation.
• Physicochemical factors.

First pass metabolism[link]

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.

See also[link]

• Enteric (disambiguation)

References[link]

v t e Routes of administration / Dosage forms Oral Digestive tract (enteral) Solids Pill Tablet Capsule Time release technology Osmotic controlled release capsule (OROS) Liquids Solution Softgel Suspension Emulsion Syrup Elixir Tincture Hydrogel Buccal / Sublabial / Sublingual Solids Orally Disintegrating Tablet (ODT) Film Lollipop Lozenges Chewing gum Liquids Mouthwash Toothpaste Ointment Oral spray Respiratory tract Solids Smoking device Dry Powder Inhaler (DPI) Liquids pressurized Metered Dose Inhaler (pMDI) Nebulizer Vaporizer Gas Oxygen mask Oxygen concentrator Anaesthetic machine Relative analgesia machine Ophthalmic / Otologic / Nasal Nasal spray Ear drops Eye drops Ointment Hydrogel Nanosphere suspension Mucoadhesive microdisc (microsphere tablet) Urogenital Ointment Pessary (vaginal suppository) Vaginal ring Vaginal douche Intrauterine device (IUD) Extra-amniotic infusion Intravesical infusion Rectal (enteral) Ointment Suppository Enema Solution Hydrogel Murphy drip Nutrient enema Dermal Ointment Liniment Paste Film Hydrogel Liposomes Transfersome vesicles Cream Lotion Lip balm Medicated shampoo Dermal patch Transdermal patch Transdermal spray Jet injector Injection / Infusion (into tissue/blood) Skin Intradermal Subcutaneous Transdermal implant Organs Intracavernous Intravitreal Intra-articular or intrasynovial injection Transscleral Central nervous system Intracerebral Intrathecal Epidural Circulatory / Musculoskeletal Intravenous Intracardiac Intramuscular Intraosseous Intraperitoneal Nanocell injection Additional explanation: Mucous membranes are used by the human body to absorb the dosage for all routes of administration, except for "Dermal" and "Injection/Infusion". Administration routes can also be grouped as Topical (local effect) or Systemic (defined as Enteral = Digestive tract/Rectal, or Parenteral = All other routes).

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