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January 15th, 2013.docx

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Dalhousie University
NESC 3237
Sean Barrett

January 15th, 2013 January-15-13 2:31 PM Factors that alter metabolism  Stimulation and depression of enzymes o Enzymes are responsible for changing the composition of molecules and making them usually more safe for the body and facilitating its elimination o There are drugs that can increase or reduce function of these enzymes o Sometimes by using the drug a lot, your body may increase the production of the drug involved  Age o As you get older, function of the liver decreases, which makes your much more sensitive to drugs that affect your metabolism  Species o Not all species metabolize all drugs in the same fashion, so the effects of drugs on metabolism between species may be different Stimulation of enzymes  Heavy drinkers have higher levels of alcohol dehydrogenase o Which is why the more you drink, the more alcohol you can tolerate  Causes metabolic tolerance o So if you're heavy drinker for many years and then quit, you'll still have this abundance of alcohol dehydrogenase  St John's Word o Used as a natural antidepressant o Works by stimulating an enzyme that is associated with the metabolism of oral contraceptives So can make your birth control ineffective  Depression of enzyme activity  Grapefruit juice can block the enzyme that destroys many drugs in the intestine (blocks first pass metabolism) o Will increase effectiveness of drugs like viagra Species differences  Many species have different enzymes and different levels of them o Very important when developing new drug and testing safety of new drug  So effects of drugs may not translate perfectly between species Age  As organisms grow and as they age enzyme levels change and different enzymes are used causing different concentrations of the drug and different metabolism  Elderly people more sensitive to drugs because of their decreased liver function Time course for blood level of drugs  Time course for absorption and excretion summed into the resultant, which is the effect of the drug you actually feel  Fast absorption causes high peaks and short duration  Slow absorption causes low peaks and long duration Therapeutic window  Require that a certain blood level be maintained, but not so high that the effects are toxic  Hard to do with rapidly absorbing drugs  So many drugs for therapeutic effects designed to release slowly over an extended period of time **Start of Lecture 2** Within-subject design  Each subject is their own control  Each subject tested in each condition  Advantages o Better control condition - no individual variation  Disadvantages o Take more time, but uses fewer subjects o possible interactions between conditions o Attrition o Carry-over effects possible Between-subject design  Subjects randomly assigned to different condition  Advantage o No interaction between conditions o Faster  Disadvantage o Need more subjects to average out between subject variation Balanced placebo design  Cross expectation with pharmacology  Involves 4 groups o Expect drug, get drug o Expect drug, get placebo o Expect placebo, get drug o Expect placebo, get placebo Three group design  Often used when testing new therapeutic drug o Placebo control o Experimental drug o Treatment with known effectiveness  Becoming less and less commonly used o Because of ethical considerations regarding the use of placebo groups in some cases, such as conditions where not treating can prove fatal, or conditions such as depression Non-experimental research  Look for relationship between two measured events, but you are not manipulating any of the variables, you just measure both  Often done as field research  This only generates correlational data, so you can not infer cause and effect relationships  So we can't say smoking causes impulsivity or that impulsivity causes smoking, just that the two are correlated Retrospective introspection  Give a drug, and ask subject to evaluate the effects they felt as a result of the drug  Results very dependent on how the questions
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