Pharmacology 2060A/B Lecture Notes - Lecture 4: Drug Metabolism, Glucuronidation, Bioavailability
15 Jul 2016
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Similarly,+ essential+ endogenous+ molecules+ synthesized+by+drug+metabolizing+ enzymes+are+shown. : note+ that+ even+ things+ like+ vegetables+ considered+ to+ be+ healthy+ would+ by+ toxic+ if+ we+ didn"t+ have+ enzymes+ to+ process+ them!+ In+most+clinical+situations+the+concentration+of+ drug+ is+ much+ lower+ than+ the+ metabolic+ capacity+of+the+body. ++in+these+situations+drug+ metabolism+displays+1st+order+kinetics. + In+ zero+ order+ kinetics,+ the+ plasma+ drug+ concentration+ is+ much+ higher+ than+ the+ metabolic+capacity+of+the+body. + Intestinal+bacteria: the+ result+ of+ 1st+ pass+ metabolism+ is+ a+ decreased+ amount+ of+ parent+ drug+ that+ enters+ systemic+ circulation. + Extraction+ratio: the+ amount+ of+ metabolism+ on+ the+ first+ pass+ through+ the+ liver+ can+ greatly+ determine+ a+ drug"s+ bioavailability. , drugs+ are+ characterized+ as+ having+ high+ or+ low+ extraction+ ratio+ (er)+ depending+ on+ how+ much+ metabolism+occurs+on+the+first+pass+through+the+liver. +++ Iv+doses+(to+compensate+for+high+first++ pass+metabolism). : small+changes+in+hepatic+enzyme++ activity+produce+large+changes+in++ bioavailability. +, very+susceptible+to+drugqdrug++ interactions++ Take+ many+ passes+ through+ the+ liver+ via+ the+ systemic+ circulation+ before+ they+ are+ completely+metabolized. +++ Phase+i+metabolism: convert+ lipophilic+ drugs+ to+ more+ polar+ molecules+ by+ introducing+ or+ unmasking+ polar+ functional+ groups+such+as+hydroxyl+(qoh)+or+amine+(qnh2). + Phase+ i+ + phase+ i+ drug+ metabolizing+ enzymes+ are+ localized+to+the+smooth+endoplasmic+reticulum+(er). +
