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Medications delivered to the distal one-third of the rectum at least partially avoid the "first pass effect" through the liver, which allows for greater bio-availability of many medications than that of the oral route. Rectal mucosa is highly vascularized tissue that allows for rapid and effective absorption of medications. [15]
First-pass metabolism may occur in the liver (for propranolol, lidocaine, clomethiazole, and nitroglycerin) or in the gut (for benzylpenicillin and insulin). [4] The four primary systems that affect the first pass effect of a drug are the enzymes of the gastrointestinal lumen, [5] gastrointestinal wall enzymes, [6] [7] [8] bacterial enzymes [5] and hepatic enzymes.
Intravascular administration does not involve absorption, and there is no loss of drug. [4] The fastest route of absorption is inhalation. [5] Absorption is a primary focus in drug development and medicinal chemistry, since a drug must be absorbed before any medicinal effects can take place. Moreover, the drug's pharmacokinetic profile can be ...
Systemic administration is a route of administration of medication, nutrition or other substance into the circulatory system so that the entire body is affected. [1] Administration can take place via enteral administration (absorption of the drug through the gastrointestinal tract) [ 2 ] or parenteral administration (generally injection ...
Furthermore, after absorption from the gastrointestinal tract, such drugs must pass to the liver, where they may be extensively altered; this is known as the first pass effect of drug metabolism. Due to the digestive activity of the stomach and intestines, the oral route is unsuitable for certain substances, such as salvinorin A .
Whether a drug is taken with or without food will also affect absorption, other drugs taken concurrently may alter absorption and first-pass metabolism, intestinal motility alters the dissolution of the drug and may affect the degree of chemical degradation of the drug by intestinal microflora.
Drug delivery systems have been around for many years, but there are a few recent applications of drug delivery that warrant 1. Drug delivery to the brain: Many drugs can be harmful when administered systemically; the brain is very sensitive to medications and can easily cause damage if a drug is administered directly into the bloodstream.
Administering medication rectally. Enteral administration is food or drug administration via the human gastrointestinal tract. This contrasts with parenteral nutrition or drug administration (Greek para, "besides" + enteros), which occurs from routes outside the GI tract, such as intravenous routes. Enteral administration involves the esophagus ...