Search results
Results from the WOW.Com Content Network
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.
Ethanol does not bind to plasma proteins or other biomolecules. [13] [2] [3] The rate of distribution depends on blood supply, [4] specifically the cross-sectional area of the local capillary bed and the blood flow per gram of tissue. [13] As such, ethanol rapidly affects the brain, liver, and kidneys, which have high blood flow. [2]
Drug metabolism is the metabolic breakdown of drugs by living organisms, usually through specialized enzymatic systems. More generally, xenobiotic metabolism (from the Greek xenos "stranger" and biotic "related to living beings") is the set of metabolic pathways that modify the chemical structure of xenobiotics, which are compounds foreign to an organism's normal biochemistry, such as any drug ...
Pharmacologists have linked drugs to glucuronic acid to allow for more effective delivery of a broad range of potential therapeutics. Sometimes toxic substances are also less toxic after glucuronidation. The conjugation of xenobiotic molecules with hydrophilic molecular species such as glucuronic acid is known as phase II metabolism.
For example, oxytocin has a half-life of typically about three minutes in the blood when given intravenously. Peripherally administered (e.g. intravenous) peptides like oxytocin cross the blood-brain-barrier very poorly, although very small amounts (< 1%) do appear to enter the central nervous system in humans when given via this route. [31]
For example, antibiotics that kill gut bacteria often reduce enterohepatic drug circulation and this requires a temporary increase of the drug's dose until the antibiotic use is discontinued and the gut repopulates with bacteria. This effect of antibiotics on enterohepatic circulation of other drugs is one of several types of drug interactions.
These drugs increase the permeability of the blood–brain barrier temporarily by increasing the osmotic pressure in the blood which loosens the tight junctions between the endothelial cells. By loosening the tight junctions normal injection of drugs through an [IV] can take place and be effective to enter the brain. [ 8 ]
The other elimination pathways are less important in the elimination of drugs, except in very specific cases, such as the respiratory tract for alcohol or anaesthetic gases. The case of mother's milk is of special importance. The liver and kidneys of newly born infants are relatively undeveloped and they are highly sensitive to a drug's toxic ...