Textbook Notes (368,629)
Canada (162,027)
Psychology (9,696)
PSYC62H3 (313)
Chapter 3

chapter 3

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Suzanne Erb

Chapter 3 PHARMACOKINETICS -The difference in potency can be explained on the basis of how easily or quickly these drugs get to their sites of action, and how quickly they induce those actions. -In order for a psychotropic drug to exert any effects on an organism, it must get to its sites of action in the nervous system. -The effects of a particular drug on an organism depend heavily on the rate of accumulation and the concentration of the drug at its sites of action and the duration of the contact at those sites. -These are a function not only of the amount of drug administered but also of its pharmacokinetic, which refers to the dynamic processes involved in the movement of drugs within biological systems with respect to the drugs absorption, distribution, binding or localization in tissues, metabolic alteration, and excretion from the body. -The field of pharmacokinetics is primarily concerned with what the body does to the drug; together these determine the type, degree, and duration of a drugs effects. -Differences among organisms in their pharmacokinetics, due to genetic differences, the presence of other drugs, disease, and physiological and psychological status, can result in 5- to 20-fold differences in their reactions to a given amount of drug within species, and 20-100 hold differences in their reactions across species. Drug Absorption -Must pass through several biological membranes -For an orally administered drug to exert an action on the brain, it must pass though a variety of biological membrane before it can reach the cells of the brain that are responsible for the drugs psychoactive properties. -several factors, such as the salt form of the drug, the particle size of the dosage form, and the suspending agent used, can affect the degree of absorption. -One of the most fundamental factors affecting the passage of molecules from one side of a membrane to the other is the relative concentration of the molecule on the two sides. -The greater the differential concentration of the molecules on the two sides, the more readily the molecules will diffuse from the site of higher concentration to the site of lower concentration. -Because biological membranes consist of lipid materials group of fats and fat like substances, the most important factor in a drugs ability to pass though these membranes is its lipid-solubility =lipophilicity that is its capability of being dissolved in fat. -Penetration into the brain may decrease if the drugs lipophylicity is too high but in general it is increases to a optimal penetration point= the faster if can get to the brain to exert the psychoactive effect. -The drug must also be somewhat soluble in water to be effectively transported by the blood stream, so it can dissolve in the plasma. -The most effective drugs are the ones that are some what soluble in oil and water. -The relative solubility in each medium is a major factor in a drugs ability to get into the brain. www.notesolution.com
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