First pass effect refers to the administration of certain drugs by the gastrointestinal tract, has not yet absorbed into the blood circulation in the intestinal mucosa and liver metabolism, leaving the prototype dose into the blood circulation to reduce the phenomenon, also known as the first hurdle effect. After oral administration of certain drugs through the intestinal mucosa and liver and subjected to inactivate metabolic, drug into the systemic circulation is reduced, reduce the efficacy effect. The phenomenon of drug effect due to the route of administration make the difference in the treatment of science is important.
first pass effect
first pass effect (First Pass Effect) also known as the first hurdle effect, the first pass effect. The absorption of all oral drugs to go through the gastrointestinal wall, and then into the portal vein. Some drugs are almost no metabolism, while others in the gastrointestinal wall or the liver is extensively metabolized, eliminate, to first-pass effect. A role to make enhance the metabolism, reducing the absorption of the treatment effect decreased. Parenteral administration such as injection, subcutaneous or sublingual administration to avoid first pass effect. Large doses of oral drugs can intestines, liver metabolism is saturated, it is assumed to absorb completely, when the dose of the oral and parenteral administration of the same blood concentration, the same effect varied widely, and intravenous injection of the same dose in the urine drug metabolism things big, that the first had occurred. cirrhosis of the liver and the portal vena cava anastomosis in patients with the role of reduced, increase drug bioavailability. This is called first-pass effect.
Overviewfirst pass effect, administration of certain drugs by the gastrointestinal tract has not yet absorbed into the blood circulation in the intestinal mucosa and liver metabolism, leaving to enter the blood
first pass effect
loop prototype drug reduced the phenomenon, also known as the first hurdle effect. After oral administration of certain drugs through the intestinal mucosa and liver and subjected to inactivate metabolic, drug into the systemic circulation is reduced, reduce the efficacy effect. The phenomenon of drug effect due to the route of administration make the difference in the treatment of science is important. Enter the large cycle of drugs reduced oral drugs through the intestine, intestinal or liver metabolism, known as the first pass effect, also known as first pass metabolism. Parts of the intestine, intestinal and liver first pass effect. Intestine, digestive juices, digestive enzymes, and even the enzyme produced by the intestinal flora can make certain drugs inactivation, such as oral insulin by protein hydrolysis enzyme is almost completely inactivating the intestinal wall because of the role of monoamine oxidase allows the tyramine failure in the intestinal wall, and if isoproterenol oral, a phenomenon known as the first-pass effect. the first pass effect by the enzyme concentration and blood velocity impact, the higher the concentration of enzyme in the liver, the blood flow faster, the first pass effect more obvious. first-pass effect is stronger, less to enter the drug in the blood. Oral medication absorbed in the gastrointestinal tract to the liver through the portal vein, some easily metabolic inactivation of drugs through the intestinal mucosa, most of the destruction of the first through the liver into the blood circulation of the effective dose to reduce, lower efficacy, which kinds of phenomena called first pass effect. Therefore, the drug in the intestinal mucosa by the inactivation of the enzyme after oral administration via the portal vein to both cases, the liver is converted to first-pass effect. acid damage to the drug occurred prior to absorption changes; drugs to plasma proteins was reversible combination, the combination of drugs biological effects without metabolic excretion, temporary storage in the blood. When the plasma concentration decreases, the combination of drugs can release the free drug, both in dynamic equilibrium; subcutaneous or intramuscular injection, the drug first along the connective tissue proliferation into the blood circulation via the capillaries and lymphatic endothelial cells.
influencing factorsdrug "first pass effect" also known as the first pass effect, the drug is absorbed reaches the systemic circulation jibei of metabolism. Can be divided into three types:
first pass effect
1, hepatic first pass effect. Can occur after oral medication, intravenous or sublingual administration can be avoided.
2, intestinal first-pass effect.
3, pulmonary first pass effect, very few drugs, such as chloroform.
double most of the oral medication will occur simultaneously digestive tract and liver first pass effect. Such as nitroglycerin, oral completely absorbed by the liver, 90% of glutathione and organic nitrate ester reductase system inactivated. nitroglycerin sublingually, it can be directly absorbed by the oral mucosa into the superior vena cava, and then to the systemic circulation, rather than the liver can play a curative effect. Sublingually 1 to 2 minutes therapeutic effect.
chlorpromazine intramuscular After, the plasma concentration than oral administration of the same dose of chlorpromazine is 3-10 times higher. The reason is because after the oral administration of chlorpromazine, the first pass by the gastrointestinal mucosa. By the first pass on the clinical, but also significantly reduce the bioavailability of the drug nitroglycerin, reserpine, propranolol, lidocaine, America metoprolol, salbutamol, Ritalin, morphine, meperidine. Aspirin, cortisone, and imipramine hydrochloride and so on.
avoid method use a model to characterize the physiological significance in vivo after intravenous and oral administration of propranolol disposal, successfully simulated after oral administration, first-pass effect on the the impact of drugs in vivo disposal process of the people the discovery of the biological use of degree significantly lower, and under certain conditions, in the propranolol oral absorption of the first pass process of its doors vein in the concentration of liver metabolic enzymes may be will generate transient ( part of) the role of saturation, nonlinear dynamics observed in the past, people of this saturation mechanism of the Department of propranolol oral reason, and this transient and saturation effects propranolol dose and dosage forms. To avoid first-pass effect:
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