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Absorption is the journey of a drug travelling from the site of administration to the site of action. [ 1 ] [ 2 ] The drug travels by some route of administration ( oral , topical-dermal , etc.) in a chosen dosage form (e.g., tablets , capsules , or in solution ). [ 3 ]
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
Drug administration via the nasal cavity yields rapid drug absorption and therapeutic effects. [33] This is because drug absorption through the nasal passages does not go through the gut before entering capillaries situated at tissue cells and then systemic circulation and such absorption route allows transport of drugs into the central nervous ...
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.
Enterohepatic circulation of drugs. Enterohepatic circulation is the circulation of biliary acids, bilirubin, drugs or other substances from the liver to the bile, followed by entry into the small intestine, absorption by the enterocyte and transport back to the liver.
Due to this, the absorption of fat-soluble vitamins may decrease. Therefore, it is recommended to take a multiple-vitamin supplement during orlistat therapy. [9] [12] Cetilistat, a new lipase inhibitor, is an experimental drug for obesity. In October 2016 the drug was still in clinical trials. [13]
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.
The conventional drug delivery system is the absorption of the drug across a biological membrane, whereas the targeted release system releases the drug in a dosage form. The advantages to the targeted release system is the reduction in the frequency of the dosages taken by the patient, having a more uniform effect of the drug, reduction of drug ...