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Drugs, their pharmacodynamics and pharmacokinetics Name: Instructor: University: Course: Code: Drugs, their pharmacodynamics and pharmacokinetics Question 1 Orally administered drugs are introduced into the system through the mouth. They move through the digestive system till they arrive at their target sites.
Here, they are absorbed into the blood through the epithelial cells and into the blood stream. From the bloodstream, they may enter the tissue fluid and then into the cell where they are metabolized and converted into active form. During this process, the drugs encounter several obstacles in their path that they have to overcome. They occur at almost every stage of the process from administering to action at the target sites. The main barriers are the cell plasma membrane, epithelial cells, endothelial cells, blood capillaries, glomerular membrane, capillaries and renal tubules among others. The plasma membrane is a lipid barrier. It only allows passage of lipophilic molecules and hydrophilic molecules, like water, into the cell. It is partially permeable to larger molecules such as larger lipophilic ones. The intestine is the main site for absorption be it drugs or food. The gastrointestinal epithelium also acts as great barrier to the movement of drugs. This layer is a single cell thick. These cells are closely packed together making it difficult to for drugs to move from the intestines into the blood stream. The layer is covered with a mucosal membrane which bars the movement and absorption of the drug. The drug has to go through two plasma membranes to get to the bloodstream. ...
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