Study Guides (238,207)
Canada (115,009)
Toxicology (18)
TOX 2000 (7)

Biomed Tox notes.pdf

61 Pages
Unlock Document

University of Guelph
TOX 2000
Nigel Bunce

Page 212BIOMEDICAL TOXICOLOGYOBJECTIVESTo understand the following conceptsToxicants and toxicity Exposure and hazardbenefitToxicokinetics including absorption distributionstorage biotransformation and eliminationMechanisms of toxicity including target specificity typesof target interaction and pathogenesisGenetic toxicology genes as a targets and DNA repair Origin and consequences of mutationsToxicity testing including general approaches and design Acute to chronic testing and specific effects testingIn vivo and in vitro testing issues in the use of animals The diet as a source of toxicants Effects of nutritional status on response to toxicantsTo demonstrate principles discussed in this section exampletoxicants will be usedEmphasis will be placed on developinga sound understanding of the basic toxicology principlescovered21TOXICANTS AND TOXICITYOur body is composed of chemicals endogenous substancesrequired for life but capable of producing illness whenproduced or ingested in excessAll living organisms areconstantly and unavoidably exposed to chemicals foreign to thebody exogenous which we now call xenobiotics and whichinclude both manmade and natural chemicalsWhen anychemical results in an adverse response the disease state isreferred to as toxicosis poisoning and the chemical isreferred to as the toxicant poisonThe question often arisesWhat substances are toxic A significant figure in thehistory of science and medicine Paracelsus 14931541answered this question in his statement All substances arepoisons there is none that is not a poisonThe right dosedifferentiates a poison from a remedyThis statement hastwo very important biomedical principles pertaining topharmacology and toxicologyThe first principle is that anadverse reaction to a chemical has a threshold dose abovewhich detrimental effects can be measured Figure 21 Simply stated all chemicals are toxic but exposure to a lowdose of a chemical does not necessarily result in poisoning The second principle is the doseresponse relationship inwhich toxic responses increase in severity known as thegraded response as the amount dosage of the toxicantincreases Figure 22This will be discussed in more detailin the section on toxicity testingPage 22Figure 21 The dependence of biological function on concentration oftrace elements such as Fe Cu and SeFigures 22 The standard dose response curve can be used inpopulations withresponding as dose increases or in anindividual with an increase in severity as dose increases Page 23Toxicity is a measure of virulence or potency of a chemicalsability to produce toxicosisThe amount of a chemical thatunder specific conditions causes adverse effects is referred toas toxicity and is determined by toxicity studies Section 26 Toxicity is expressed as milligrams of toxicant per kilogram ofbody weight that will produce a toxic responseThe toxicendpoint may be death lethal dose LD or some other adversebiological response ranging from reduced weight gain tohepatotoxicityTerms used to define toxicity include LethalDose LD or LD and Toxiceffect Dose TD50550HepatotoxicityThe various percentages attached indicatedoses required to cause the adverse effect to that percentage oftest animalsSuch data assists medical toxicologists inpredicting the severity of toxicosis after an exposure to atoxicantThe preferred approach however is to avoidtoxicosis and to use toxicity data to determine safe levels ofchemical exposure Figure 23Figure 23 Use of Dose response curves to demonstrate safetyof a drug and TD toxicity data is helpful but oneIn such cases LD5050wishes to know the dose at which no adverse effects occur Terms such as Maximum Tolerated Dose MTD and NoObserved Effect Level NOEL have been generated inlaboratory animal studiesThese values however arestatistically less reliable and are also prone to extrapolationerror when considering human exposureNote that the
More Less

Related notes for TOX 2000

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.