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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 ]
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.
The drug methotrexate (bottom) is an antimetabolite that interferes with the metabolism of folic acid (top) An antimetabolite is a chemical that inhibits the use of a metabolite , which is another chemical that is part of normal metabolism . [ 1 ]
Without folic acid, bacteria cannot grow and divide. Therefore, because of sulfa drugs' competitive inhibition, they are excellent antibacterial agents. An example of competitive inhibition was demonstrated experimentally for the enzyme succinic dehydrogenase, which catalyzes the oxidation of succinate to fumarate in the Krebs cycle.
Beta blockers exert their pharmacological effect, decreased heart rate, by binding to and competitively antagonising a type of receptor called beta adrenoceptors. [1]In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect. [2]
The lower the EC 50, the less the concentration of a drug is required to produce 50% of maximum effect and the higher the potency. The EC 10 and EC 90 concentrations to induce 10% and 90% maximal responses are defined similarly. There is a wide range of EC 50 values of drugs; they are typically
The «renal clearance» rate will be determined by factors such as the degree of plasma protein binding as the drug will only be filtered out if it is in the unbound free form, the degree of saturation of the transporters (active secretion depends on transporter proteins that can become saturated) or the number of functioning nephrons (hence ...
Drug design, often referred to as rational drug design or simply rational design, is the inventive process of finding new medications based on the knowledge of a biological target. [1] The drug is most commonly an organic small molecule that activates or inhibits the function of a biomolecule such as a protein , which in turn results in a ...