Transcript for:
Principles of Drug Action Overview

all right so today we're going to do chapters four five and eight which is our principles of drug action so we're going to talk all about how your body um uses the drugs the pharmaco kinetics the phaco dynamic phases the um how a drug becomes a drug um and how we have to talk about how it affects our older population okay make sure you understand which Pages you're reading you're good all right so pharmacokinetics pharmacokinetics is the study of drugs uh how it moves to the body okay we know we the reason we do this is because we want to be able to predict the actions and side effects and all of these things we watch it how it affects the body and all these side effects because we know if it works on this then it may do that that's the whole point okay all right so I'm um we're going to talk about the four categories of Pho kinetics in just a second but we our greatest barrier for any drugs is crossing many membranes we know there's different membranes right there's your blood brain barrier there's your fental um the placental barrier right these are sometimes good things sometimes we need to get past them right we want our bab we want our brain to get treated for the brain tumor so we have to be able to cross the barrier um and we're going to talk about this okay absorption desription distribution metabolism and excretion that's all what we were just saying on this other page I'm not going to read it because you can read it's basically what we're about to talk about absorption so this is how it moves from the side of administration across body membranes to your bloodstream okay so when I get my medication through my mouth then I get my medication through IV I all those things how long does it take for it to get into my bloodstream okay that is absorption the formulation is the biggest Factor okay this is um what we're going talk so our liquids we know our liquid tablet our liquid po medicines work really fast over our po medications our enteric coated delayed release they may take longer okay so our formulation is a big one um I know when I was a kid and I had like an allergic reaction my mom always gave me badril um the liquid badril because she says it worked faster and it does because it doesn't your body doesn't have to naturally break down the capsule or the pill or whatever it's already broken down for it and it's easier to absorb that way um our doses can affect our absorption obviously if we have a high dose versus a low dose versus you know inter Coatings versus things like that because it's how long the body has to break it down okay our route of administration our fastest route of administration for absorption is IV period okay then it's Im so intramuscular so our intravascular or IV is first next is intramuscular okay because we know our muscles have a lot of blood flow okay they have a lot of vessels right there that's why we give you a shot of Naran okay if we need you to wake up okay and then subq then po then transdermal okay uh so it can get slower and slower and slower we know PO is one of the slowest forms okay the size of the drug molecule that again goes with dose in the drug formulation um the surface area of absorption site so that's what we're talking about subq sometimes when you give something subq you know you're giving it in that fat tissue okay a lot people have different amounts of fat tissue okay if we have a very obese patient um with a BMI of very high BMI right we have a lot of fat tissue it's going to obviously take a long time for that medication to absorb all the way down through the subq fat and into the bloodstream okay so and that's the surface area Okay digestive motility if my stomach isn't moving if my colon if my intestines aren't making um stool it may take longer for them to work okay blood flow is another one if um especially IV or IM right if it's getting the bloodstream but the bloodstream is slow it's GNA only pick up what it can okay and keep going and then it's got still got to take it to where it's going so it delays absorption um also food food is a big one if we take our medications on empty stomachs we usually increase the r the absorption okay and if we take it on full sto um if we take it on a full stomach we decrease the absorption because then our body has to absorb all of the food digest all the food and then the pill okay so that's why a lot of these medications we like you to take them on an empty stomach okay all right so the degree of ionization this just means basically if your stomach if your medication is acidic and your stomach acid is an acid okay it's actually easier to absorb into the bloodstream because it doesn't have to over that acid base balance to break it down that's why a lot of times they're inter coated because salicylic acid is an acid okay and if it's more alkaline then we have to fix it okay um so the pH of the local environment the pH of the medication itself can also affect drug um absorption we talked about the Foods um and then dietary and herbal supplements okay we should have drug and Drug to drug interactions a lot of drugs interact with each other especially if you give them at the same time and the same stomach an acids are the worst okay because they decrease the pH of your stomach an acids neutralize your stomach acid right that's how they work okay and if my stomach acid isn't acid anymore it might not can break down the same the pill right because the pill has got that coating and it needs the acid to break it down for it to work we is a big one same thing for Herbal products and our dietary supplements we know that um we cannot take herbal supplements at the same time and sometimes you can't take them at all not just the same time but take them at all together because it will increase um or decrease the absorption of the medication okay all right so distribution is now we've got it in our bloodstream and this is how it gets to where it's got to go this is the transport the distribution Center okay um the simplest Factor determining distribution is blood flow to body tissues okay if I have poor Venus or arterial blood flow I cannot get it there fast okay if I have all this Arro arthos sclerosis if I have plots if I have um excess plaque if I just have a poor working heart okay it's going to delay the distribution it's not going to get it to where I need it to go fast um and then we also have certain tissues like our bone area our teeth eyes fat tissue it loves to just snatch up those drugs and take them we don't like that because I want my drugs to work okay so that's another reason that's another thing when they're developing the drug they have to figure out how to overcome okay um so many drug Mo many drug molecules form drug protein complexes they bind to the plasma proteins and never reach the target cells so what this is talking about okay sorry is that when you absorb the medication the medication um you're absorbing it you broke it down now you've got all these particles or these like little molecules of the drug okay the molecules pick up a partner that protein complex sometimes the protein complex is too big all right if it binds and it can't get it off it says whoa this is a stage five Clinger I can't get rid of you and the protein complex is huge then it can't get through those membranes okay then it never gets to where it needs to go that's all it's saying these are things that can affect distribution if we have a high uh protein bound drug we may have this problem okay if it can't cross that capillary membrane if it can't cross a membrane in general it can't get to that body tissue okay that's all it's saying this other one is um saying that drugs and other chemicals that complete compete for the same binding sites increase the risk of toxicity so what that means is when we have a let's say we have a medication let's say it's ke um I'm sorry not chemo let's say we have we give you morphine and Fentanyl for some reason we gave you both okay both of these work on moo and Kappa and Delta they both work on mo one of the three pain receptors okay or all of them if I have two drugs competing for that same receptor that's how it works right it sits on the receptor okay if they're all competing from this we're going to have more of this fentanyl everywhere or we're going to have more of those moo Kappa and Deltas being triggered right and we know that if we give you two forms of the same medic uh uh two medications that compete for the same receptors or binding sites we can overdose right that's all it's saying okay so whether this is drug to drug drug to Food Drug to herbal supplements that's why we have to monitor what you're getting in addition to these medications okay um we can and displacement we're going to talk about displacement right now so addition so addition means that they adds together so this is when you give two medications and the two medications uh add to each other and provide better relief so I think of like my combo narcotics like my hydrocodone acetominophen which is like lurap or Norco right the reason they're combin comboed is because they add to each other and the addition will um so now it works on both my moo Kappa Delta receptors and it works on these in my brain to dilate think the way as the way Tylenol works so it's providing better coverage of my pain synergism is um it increases the effects of the drug and you're going to say well isn't that addition okay the way your book explains it is addition is 1 plus one is two I know addition synergism is 1 + 1 is seven okay somehow when you add these two together you're getting this increased in fact I can't think of a medication that does that but this it can happen Okay when you're giving the two drugs together and it increases the effects tfold the antagonisms that's their uh antagonists just like in a book That's What's blocking it okay so sometimes we give antagonists because we want that move we want those receptors to be blocked so nothing can sit there and it says hey I'm sitting here you can't so we are blocking it so we don't have that reaction so like the best one I think of is are um beta blockers okay so beta blockers I mean they literally block they block the beta receptors from being triggered when you're blocking beta receptors you're blocking that fight ORF flight so a lot of times when you have anxiety like when I went in to the doctor for nursing school they told me that I had anxiety they said do you want a beta blocker and I said no because I don't want to mess up my heart okay um because that's we'll get there but I said no not really but the reason that they offered that is because when you're about to go take a nursing test your fight ORF flight and that anxiety is being triggered okay your fight or flight's being triggered you're you're anxious you're sweating you're you know shaking all these things because you think you're about to have to attack this beay but it's really just a nursing test you don't need all that so if we give a beta blocker it'll block that response from happening and then you block that that response okay so then you're not anxious anymore um our displacements that's for our receptors so our receptor sitting here like this okay it's filled with morphine our moo and our Kappa with our morphine okay so the receptor is being triggered it's releasing it's a opiate right it's telling your body to relieve the pain if I overdose on the morphine I need something to kick that out and move it away and it needs to sit there that's Narin nxone okay so displacement means it literally removes whatever's sitting there and it sits there and nothing else can and it'll block it until it wears off okay that's how it works all right we've talked about these blood the barriers right the blood brain brain and the fetal placental barrier sometimes they're a good thing right we don't want all of our drugs to affect our babies or to affect our brains but sometimes we do need to them them to affect it right so if my baby was in stress um they would give me me the medication because and they that's the kind of medication you want to pass because I want my they're not going to inject my baby directly through my stomach right okay that's the whole point sometimes we need to sometimes we don't things we have to talk about when we talk about distribution all right metabolism so metabolism is how your body um breaks down the drug and gets it ready for excretion okay your liver is the primary site don't even worry about anything else where does it work your liver okay so if my liver doesn't work it can't do this and then we become toxic let's talk about it so our hepatic enzyme I don't care what enzyme it is don't worry about that right and inactivates it where does it work the liver okay your liver does this your liver inactivates the drug your liver acceler we just talked about this it breaks it down it adds those protein molecules on it so that the proteins can go to the um kidney and they signal it for excretion that's it okay so we can have um enzyme induction and enzyme Inhibitors so when we have this is talking about the the hepatic enzyme okay if I have an enzyme induction so or which means induce induction means to start okay so this will increase the metabolic uh activity of the liver we need to know when drugs do that okay because is it just stimulating your liver to accelerate just for the strug no it's excreting it it's telling your liver to accelerate period so medications that can induce your um hepatic enzymes that means that you're going to burn through a lot of stuff very fast that's important so like if I give you morphine and then I give you an enzyme induction medic medication has an enzyme induction I may burn through that morphine a lot faster than someone who's not on those kinds of medicines then they're going to need more pain medicine more often okay that's important to know our Inhibitors these are the bad ones okay these are the ones that are blocking or stopping the enzyme from um from working okay so they're basically reducing the metabolic activity of the liver so if your liver is not metabolizing the medication it's not just metabol not metabolizing that medicine it's not metabolizing any medicine so now we're going to have an over um not overdose but we can have an overdose okay we have a toxic level of medication in our bloodstream and then because our bodies cannot metabolize it to get it ready for excretion we have toxicity we don't like toxicity because that's when we have all those really really bad side effects okay if my liver doesn't work all right what we're talk about right here your metabolic activity may be decreased in patients that are older and their infants if they have severe liver disease and liver disease that's like therosis hepatitis um liver failure things like that okay so these patients we have to monitor how much drugs we're giving them if their liver is not working that means that they're not metabolizing the drug they're going to become toxic okay I got to write that hepatitis down okay it can also be genetic pharmacogenetics is the study of genetic variation okay pharmaco pH Pharmacy genetics genetic disorders sometimes especially um sometimes genes can play a factor in how well your body metabolizes um I know in level two we're going to talk about psych drugs okay a lot of Psych drugs have um an interaction with if you have any kind of Asian a specific Asian descendant Gene um you can't take them because you cannot metabolize them so you don't become toxic or they don't work at all okay that's all it means okay dosage is in patients with decreased metabolic activity that means all these okay need reduced doses they the doses dosages must be reduced so we don't decide that nurses don't re decide that but I do recognize that before I kill someone okay all right so our first pass effect so this there are medications that have first pass effects this is a very confusing thing for a lot of you but okay your body um you take the pill your body absorbs it okay it distributes it to where it needs to go but when it gets to your liver okay which one which one thing we did not talk about is sometimes your medication needs to be metabolized for it to work okay sometimes it has to have that extra protein molecule P then when you take it to wherever it's going it finally works sometimes that happens this is talking about I absorb it my hepatic circulation and goes to the liver the liver metabolizes it but when it metabolizes it it inactivates it so when it inactivates it it leaves the liver and it goes into the circulation and then they basically don't work okay there's a lot of medications that have that first pass effect okay not the same thing as a first dose phenomenon it's a first pass effect um so there are ways to get overcome this if you have this if this medication doesn't work the first time you get take it okay if it's not working at all your body's realizes what it is and it's saying hey I I already to got rid of you get out and it never your body can never use the medication you can give them more of the dose a higher dose or you can change the route bual and IV have a decreased um risk of having that first pass effect because mainly this is oral so if you increase the dose so instead of taking two we take 4 milligram okay in if we give it IV over or bual over oral this can decrease this risk from happening okay all right so now we have excretion excretion happens where in the kidneys because that's how you get rid of things okay but what can your body get rid of it can get rid of free drugs so any kind of extra drug you have it's too much it gets rid of it water Sol ible agents electrolytes small molecules okay not large ones small ones that is what's filtered by the kidneys that is what's able to be excreted by the kidneys okay so drugs with um Dr drug protein complexes and large large substances are secreted in the distal tube of um of nefron what that means is that if it's really big it's going to take a little bit longer for it to be secreted okay that's all it means if my kidneys don't work can I get rid of it no I'm going to need that lower dose okay if I'm in renal failure if I have some kind of diminished excretion if I'm a child if I'm an older person I may need a lower dose because I don't want to become toxic right and when we talk about that how would you know someone's in renal failure well besides they tell you um we're checking our kidney function those kidney function tests your liver function tests that's your lfts so lft's liver function test okay so that's your a and your alt and for your kidney that's your bu in your creatinine or your GFR one of the three all three doesn't matter we're checking one of them okay they would be elevated cross the that would be kidney um dysfunction okay alter kidney function and that means that we might need to have a lower dose okay your respiratory system you can breathe off medications um you can sweat off medications you can get rid of it in your bile which means through your stool so I if anyone's ever been around someone with that's just had surgery a lot of times they have surgery and then they put that mask on them and then they take it off right and they're waking up and I swear you can just smell it on their breath the the the gas smells awful I can't it smells horribly I don't like it um but your body is just trying to get rid of it because it's trying to wake up um we all know that when you drink alcohol next day you sweat you have the alcohol sweats okay you're sweating off that alcohol that's what we're talking about when you're sweating off the medications okay all right so now we're going to talk about blood concentration so we the minimum effect of concentration when we talk about concentration we're talking about plasma concentration which means in your blood okay so when they draw your blood levels of them they can draw a specific um test that tests the blood levels um of a medication okay so it'll be like a vamin that's what it is it measures how much vcomin which is a medication is in your blood or whatever okay our minimum effect of concentration is the amount of drug required to produce a therapeutic effect sometimes it's a good thing sometimes we like a minimum effective dose because we don't want to overdose them our toxic concentrations are the ones when we have those serious adverse reactions and then the therapeutic that's a sweet spot it's neither minimum or toxic we're right in the middle we love a therapeutic range or therapeutic um sorry a therapeutic index okay our therapeutic index that tells you how much um make sure this is somewhere on here yeah a therapeutic index so we can have a narrow therapeutic range or a wide therapeutic range okay um if we have a wide one that's great I think this is somewhere in here but we're going to talk about it right now you have a wide therapeutic range that means I can take 1 milligram or 100 milligrams and I'm good I'm not going to become toxic I have a big window to give you enough coverage to do whatever I want you to do if we have this a narrow meaning I have one to like five milligrams I can give you before you overdose we have got to um pay attention Okay we're going to talk about the next slide about how we pay attention to those but um that means that we have a they're not safe okay they need extra blood levels we need to make sure we're monitoring those blood levels of that medication because we have such a narrow therapeutic index or a narrow therapeutic range that if we go over or under we will kill someone okay bad things we don't like doing that okay all right so onset I mean it is what it is so that's onset is how long it takes for your body to produce an effect therapeutic effect your Peak is the highest concentration of of medication in your blood the duration is how long it takes for the drug um how long the medication remains therapeutic okay not how long it stays in your system how long it remains therapeutic half life is the length of time needed to decrease the plasma level by 1/ half so that's telling you how long it's staying in your body okay um and then our trough is our lowest concentration so let's let's go over this let's make it really simple onset that cuz what's the first question they're going to ask you after you push that morphine how long do I have until this works okay that's your onset how long it takes to work so we know that IV is the fastest right I IM is the second fastest then we get into um subq Po and trans and then our other routes okay our Peak we're going to peek and trough together our duration how let mean tell that tells me how long I may I need an um peek and I'm sorry duration in halflife tell me how long it's going to take number one how long is it going to how long is it going to last so how long is this morphine going to last okay it should last for you know two hours right but I know that I can't give them another dose until it's 4 hours that is because of the halflife so if it takes you know 2 hours for the half the um the half life of the drug takes two hours that means in two hours I will have half the concentration in my blood that means in two more hours I will not have any more of the drug in my system meaning that I can take another dose okay so your duration and your halflife they kind of go together so this tells me how long it's going to work is the duration your halflife is how long it's staying in my body which is important because if it's going to stay in my body for a really long time time I can't just give you another dose whenever it wears off okay because if you still have more of it circulating around we can become toxic so those kind of go hand in hand and then our Peaks and our troughs so our Peak is our highest our trough is our lowest okay we talked about that um so when we measure Peaks and troughs that's important to measure with our medications that have that narrow therapeutic index okay especially our IV versions because if we are still have that high plasma concentration if our concentration is still up here that Peak is still happening because our kidneys don't work because we have some kind of alteration in something and then you give them another dose of the medication and my PE and I'm still at my Peak that means you basically overdose them okay so we measure troughs before like 30 minutes before you give an IV meas medication we measure our Peaks after Administration so that's 15 to 30 minutes um for IV 30 minutes to 1 hour for IM and 1 hour for po I'm going to say it one more time 15 to 30 minutes after completion of the IV medication 30 minutes to an hour after I am Administration and one hour after po Administration that's when we should have our Peaks that's when we should see the highest amount available in our blood we measure our troughs like 15 30 minutes before we give our next dose to make sure that we're still don't have this High concentration okay we measure a trough before to make sure that they're low okay and we've talked about our you know that tells you the the the bioavailability how fast it's going to work the on the onset and the peak right so R IV i m then po all right so how drugs reach and maintain therapeutic effects so let's talk about this we like drugs to take drugs every day right if you have a blood pressure medication we usually to take it every day that reason why is because we wanted to maintain this therapeutic range okay um so let's talk about what that means the loading dose loading doses are um when you give the the biggest one that I give for a low like this is like a bolus okay hein's A big one if you give Hein Ivy we give you a big old fat bolus and then like over a minute or two and then we keep you on that maintenance dose okay so let's go to maintenance dose and we'll come back maintenance dose is keep giving the drug whether it's IV po subq whatever it is you're maintaining that drug concentration in that therapeutic range and you're allowing it to to keep working and working and working and not letting that halflife um not letting it become toxic but also not letting it wear off okay that's what a maintenance dose does our loading doses that's how we quickly get you to that therapeutic range so that's why we give you that Bolis that we might like give that high dose of it right and that way we get to that maintenance easier and then we can maintain it and keep it going because like heprin thins your blood we like heprin to thin your blood so if we need to give you Bist heprin and then we maintain we get that therapeutic effect of our blood is thin and it's dissolving the clot then we can maintain that dose and keep going and we can dissolve the clot until it's gone but we've got to get there so instead of taking three days we just Bolis it for you okay safely but we do all right so pharmacodynamics is how medicine changes in your body um it helps produce I'm sorry helps predict if the drug will produce a change we're going to talk about it right so when we're talking about those um how a drug becomes a drug and it's doing all those clinical investigations and we're we're studying how it works on the body before we give it to a bunch of people this is what we're talking about all right if you haven't had um statistics you may not know what I'm talking about but I'm going to talk about a bell curve which is just like this okay okay I'll see if I can find a piece of paper and show you um it looks like a belt okay it has a peak and it has two sides when you use it this is a bell curve okay this is what we're talking about right so this is a uh our frequency distribution this is our graphical representation of the number of patients responding to the drug at different doses so the peak of the curve the top of it indicates the largest number of patients that respond to the drug these outliers um mean that they're not they don't respond to it okay what this doesn't tell you is how big the response is so let's say we're we're measuring the effectiveness of morphine you know I love everyone knows what morphine is okay so I gave everybody on the in this 100 patients I gave 100 patients 5 milligrams of morphine 50% or a lot of more than 50% had a response these people had either too much of a response or not not enough of a response okay but or didn't have a response at all I should say so if I measured everyone's Pain Scale 0 to 10 these people would still be zero these PE I mean still be a 10 so I went from a 10 out of every one of these 100 patients had a 10 out of 10 pain okay I gave them 5 milligrams of morphine these did not have a change after I gave them morphine and I reassessed the appropriate time um they stilled 10 out of 10 pain these patients overdosed okay these patients didn't have I'm sorry didn't they didn't overdose because it doesn't tell you the magnitude these patients didn't have a response either but it could be good could be bad this the peak okay this means that my pain went lower didn't doesn't know how much because it doesn't tell me that it just went lower so you get a check basically instead of it being on like a a number scale it's like a yes your pain went lower no your pain didn't so that these are the NOS this is the yes so whether my pain went from a nine out of um from a 10 to a 10 to a nine out of 10 or whether my pain went from a 10 out of 10 to a zero out of 10 it's right here we all get put in the same spot okay our median effective dose this means that when we put it on our frequency distribution curve that the these amount of people have that therapeutic response okay this is how we get our average or our standing doses so we gave a 100 people this specific dose at least 50% of them had the response we wanted to these people might have had too much it might have been too much for them these people might not have been enough but at least 50% had a good therapeutic response that we wanted this does work that's why some people require more some people require less okay I might only need 2 milligrams of morphine you may need six milligrams of morphine but 50% of people said that four milligrams of morphine works for them that's what it's saying our median lethal dose so we don't test this on humans so this is we test this like on human cells or on animals okay not humans so this amount of drug killed everyone this one I don't know what this side tells you but these people didn't die but 50% of the people did die that's all it means okay that's where we get our our um toxicity ranges from okay our medium toxicity R dose this means that 50% started having those adverse toxic effects okay right so these were due test on humans um because it's not lethal we don't test the lethal on anybody this is what we test them on so 50% of student um of the patients had some kind of um altered function or toxicity effect okay we already talked about this drug safety margin or the therapeutic index arrange we were just talking about how that narrow therapeutic index causes a um the N the more narrow the therapeutic index the more unsafe the medication can be the more serum lab tests we have to do the more checking we have to do for the patients the wide therapeutic index is good all right so now we're going to have these lovely curve okay I'm going to show you how what this one looks like okay so this is our um three phases of our graded response curve this is what we're talking about phase one is down here okay so this means that we give you five milligrams of this medication and a few of the cells are targeted but not all the ones we want to I think of this as chemo okay we we don't want it to um you know kill you but we also want it to work so this isn't this isn't targeting enough cells so we give you a little more so now we're giving you 10 or 15 milligrams okay this is where we want to be this means that there is going to be a safe amount of drug administered and that it is targeting the amount of cells we want to and we're having that therapeutic response when we get to that Plateau that means that there is no therapeutic effects have increased that means I'm not targeting any more cells than I want to right it's still the same amount of cells are being targeted but I may have an increased risk of adverse effects this is where I get toxic okay all right zombies potency means how strong it is right some medications have a higher post potency than others um doesn't mean they work you know better May mean that they have that wide or narrow therapeutic index our efficacy is how well it works okay so it's the magnitude of re of maximal response that can be produced by a by a specific drug how well it works okay all right so we've kind of talked about this already but we've t talk about how medications they sit on those receptors okay our um specific drugs versus our non-specific drugs our specific drugs are going to sit on this one receptor only and never touch anything else okay we like it when that happens because that means that it's only going to work right here okay our non-specific drugs these work on multiple receptors that's not always a great thing that means increased risk of side effects right if I'm hitting multiple different cells or multiple different receptors that means I may have more side side effects so we talk about beta blockers that's a big one that we talk about sometimes they're not selective maybe it works on beta 1 and beta 2 now we're working on two different receptors now we're having double the side effects okay or my chemo all right chemo is a big one for those non-specific um medications because our non if we have um chemom medication our chemo drugs or our chemotherapy right that kills cancer it it stops um a lot of them stop cell growth okay and a lot of them are not specific so they stop all cell growth that's why you lose your hair because it can't make new replications of cells to make hair that's what your hair is okay um yeah so that's why you lose your hair that's why you might have um decreased white blood cells that I you have this have that have this have that because chemo has a very broad um or non-specific receptor or non-specific action okay we like drugs that have specific actions because we know exactly how they're going to work where they're going to work and what side effects to look for okay so agonists our agonists are things that bind to the receptor and produce the same response so this is our um this is our BFFs okay these are our impersonators that are really good right they sit on in that in the receptor they look just like the thing that normally sits there looks right and it produces the same or even better results we like agonists the good impersonators our partial agonists those are our cheap impersonators we don't they work but they're not great okay so when they bind to the receptor it at least allows them to sit there okay but they don't prod they don't make the big bucks they're not the good personages so they're weak they don't they're not as effective as the agonists okay and then we have our antagonists this is the bully okay our bully is going to sit in that receptor or tell you you know it sits in that receptor and it says I'm sitting here you can't sit here n boo boo and then when it sits in that receptor it doesn't stimulate the receptor's response so it blocks all those receptors that have that key fit that say stimulate this response it's it allows um think of it like an access to to a door okay our agonists have a perfect key it has that master key okay it means it's going to work no matter what I put it in the key slot and I turn it it's going to turn every time our partial agonists that means it's going to be similar to the master key but it doesn't work on all the doors okay it doesn't produce the same effects the door doesn't always open our antagonists are when someone tries to break into your house okay so I have what I thought I thought I stole the right key but I didn't it fits in the slot but it won't turn okay and so when it won't turn or doesn't stimulate the resp response nothing else can sit in the slot when I still have the key in there right so it blocks all the other things from sitting on the receptor and then it doesn't initiate the key your car to start or your door to open or whatever it's supposed to do so it blocks it and it doesn't produce that effect okay some this is a good we talked about how antagonists are good sometimes we need that block to happen so that we don't you know if I'm drunk and I put the wrong key in the in the slot for my car and it doesn't CR prank I might just give up and call an Uber right that's a good thing because I shouldn't drive drunk but that's what antagonist does all right so now old people old people are at super big risk for um altered pharmacokinetics their kidneys don't work their livers don't work they take a bajillion meds they counteract with each other they have an increased risk of adverse effects because they cannot get the body get it out so how does it um affect them sorry I lost my place in my nose um yeah so these people may need lower doses right okay diminished gastric motility that's a big one right my everything slows down every one of your old patients is constipated all of them okay because the gastric motility the muscles get tired stop doing it it's why you get constipated you have an increased risk gastric pH so it doesn't absorb the drugs like you're supposed to right it over absorbs them or it um doesn't break them down like they're supposed to okay and if my stomach's not going anywhere the the medications cannot get absorbed and can't go anywhere we also have diminished distribution because we have lots we have a lot more fat because we reduce our muscle mass and we increase our body fat we have less water less plasma we have a decreased cardiac output so my H my my heart can't pump all that stuff where it needs to go and so now it can't it can't get it out okay can't get it to those target cells that increased body fats a big one especially with our subq right because we know the body surface area can um if we have lots a lot more fat that means a lot less um blood flow to the areas right so it takes it longer to get distributed and if we have more body fat we may have more fat in our vessels right that's more plaque slows down distribution our livers suck okay they have a reduced first pass effect that's good right so good and bad right so if we know if we if it has a first pass effect so they double the dose and then you give it to old person they may overdose right that's bad but it also may work well they don't need a high dose right these people with our decreased metabolism and excretion they need lower doses because they don't their liver doesn't work it doesn't metabolize to drugs that means we have more drugs hanging out in our system and we have more drugs hanging out in our system we become what toxic okay our Half-Life increases so that means it takes it longer for it to get rid of it which means we were going to be what toxic excretion um excretion also our kidneys are not filtering good are not filtering well our blood flow to our kidneys isn't great that means that they're not going to work great everything's decreased okay that means we aren't going to be able to excrete these drugs which means if we have more drugs hanging out in our system what are we going to become toxic so what do we need to measure before we give medications to any of these patients our liver function tests and our kidney function tests so our be our creatinine our GFR for our kidneys our a or alt for our liver okay that is what it's for all right that is the end of drug action thank God all right good luck you have any questions put them in the discussion board