foreign introduction to pharmacology and introduce you to one of the fundamental concepts which is pharmacodynamics we're going to break down what a drug is how drugs produce their effects on the body and introduce you to the different types of drug targets and then in later pharmacodynamics lectures we're going to expand on these topics all right so first of all what is a drug in Pharmacology a drug is a chemical substance that when administered to a living organism produces a biological effect drugs can be used for therapeutic purposes to treat diseases or they can be used for non-therapeutic purposes such as recreational or experimental use this also includes the caffeine in your coffee on an ice latte now and it also includes experimental tools that are used in researching diseases or finding new therapeutic treatments now medicine is what we usually refer to as a drug that is used to treat cure or alleviate a diseases symptoms these are what we refer to as therapeutic drugs or therapeutic agents and a lot of medicines actually contain more than one active ingredient so there will be a lot of other things in a therapeutic formulation so it may contain other substances such as stabilizers or solvents for example a brand of medication used to treat high blood pressure might contain two different types of blood pressure lowering drugs in a single pill okay another example that we might consider a drug might be something like a Venom or a toxin because these substances produce a biological effect on a living organism so a poison is a substance that causes a harmful effect on the body but the thing is the difference between a drug or medicine and a poison might be in the dose if a substance is taken at therapeutic levels it's very safe and effective but if taken in overdose it can lead to dangerous outcomes such as liver damage and failure and we're going to break this down in later lectures where we cover concentration response relationships and the relationship between the dose of a drug that's given and the effect it has so that's the definition of a drug the question now is how are drugs classified drugs can be classified in different ways based on their chemical structure mechanism of action which is how the drug achieves its biological effects okay so how the drug does what it does for example going back to lowering blood pressure how does it lower blood pressure another way is based on therapeutic use so what is the drug designed to do for example drugs can be classified as depressants analgesics or antibiotics based on their effects on the body okay so then how do you name drugs because many drugs have multiple different names there are three main systems for naming drugs we have chemical generic and proprietary chemical names are based on the Drug's chemical structure and are often complex and difficult to remember they are primarily used by chemists and researchers so it's not really used when talking about the medications that are given to patients next are generic names which are simpler names given to drugs by Regulatory Agencies ones that have been approved for use these names are not owned by any particular company and are used by multiple manufacturers now it's really important for these approved names to be different from each other this is to avoid confusion with other drugs that are already approved and on the market because we don't want to prescribe One Drug to a patient who ends up being given another drug that has similar sound or spelling to it that is a completely different effect and then we have proprietary names also known as brand names okay so these are created by drug companies and are used to Market their products these names are protected by trademarks and are unique to a particular product essentially the naming systems have different characteristics and uses chemical names are important for research and development while generic names are important for prescribing and dispensing drugs and proprietary names are important for marketing and brand recognition let's go through an example so here we have an example for a very commonly used drug if you're a medicinal chemist then you will tell you a lot about the drug but if you aren't then not really now if we were to use a generic name or a trade name most people would be familiar with the drug the generic name for this compound is ibuprofen ibuprofen is the approved name suggested by the manufacturer and approved by the regulatory authority to use and describe the chemical entity if you aren't familiar with ibuprofen then you are likely to be familiar with at least one of the trade or brand names for this drug one of the trade names is nurofen another is Advil it's the same chemical entity but it is manufactured and marketed by two different pharmaceutical companies you can see the differences between chemical name generic name and trade name all right so if coveted water drug is and the different systems that are used to classify drugs let's now subtract complexity and start to look at how drugs produce their effects within the body we're going to introduce pharmacodynamics which is the study of how drugs produce their biological effects and how drugs will affect the different systems of the body it involves understanding the interactions between drugs and their target receptors enzymes and other molecules in the body and how these interactions lead to changes in cellular function organ function and ultimately the overall response of the organism but before we start breaking this down why is this important because there's no point in going through this without actually asking what our purpose is here so why is pharmacodynamics important well because understanding pharmacodynamics is important for the development of safe and effective drugs by studying how drugs interact with the body we can predict their effects optimize their thirsting regimenes and minimize their potential for adverse reactions okay so then how does a drug exert its effects on the body it does this by modifying existing processes including physiological or biochemical processes a lot of drugs exert their effects via specific chemical interactions or covalent bonds hydrophobic interactions or electrostatic okay with particular molecular targets drug targets can be proteins enzymes receptors or other cellular components which will break down later in this lecture so the drug is going to bind to the Target molecule which then modifies the function of its molecular Target to produce a biological effect so either activate or inhibit its function leading to a physiological response the ability of a particular drug to bind to its molecular Target is determined by both the structure of the drug and the structure of the molecular Target okay and the type of interactions formed between the drug and its Target is important as well one thing I want to point out is that there are drugs that produce their effects on the body by acting on simple physical or chemical processes these are called non-selective interactions or effects what this means is that these drugs aren't interacting with a specific molecular Target but instead are modifying a more General physical or chemical process let's go through some examples a great example are antacids like calcium carbonate or magnesium hydroxide which are commonly used for indigestion these don't have a particular molecular Target but rather they modify a chemical process within the body they work by neutralizing stomach acid through a simple chemical reaction so they don't Target any specific molecule or pathway there are weak base that acts on the acidic environment of the stomach because your stomach produces large amounts of hydrochloric acid which AIDS in the digestion of food so the hydrochloric acid in the stomach will react directly with the antacid and therefore the acid will become neutralized so you will end up with a reduction in the acidity of the stomach that's pretty cool okay so there's our antacids another example of a type of drug that exerts is effect by modifying a non-selective process are asthmatic agents an example is osmotic laxatives which you may know are useful the treatment of constipation okay but they're also used for the preparation of particular GI procedures such as a colonoscopy so what these osmotic laxatives do is they're going to draw water into the colon which increases the bulk and softness of stool promoting bowel movements this effect is not due to any specific interaction with a drug Target but rather to the physical process of water movement okay so these laxatives contain molecules that are difficult for the GI tract to absorb so there's going to be a higher concentration of these molecules that stay within the GI tract so there's going to be an increase in soil concentration inside the GI tract which then stimulates osmotic activity because water follows solute so what happens is it's going to cause water to move from the gut capillaries into the inside of the GI tract okay so that's how laxatives work both antacids and osmotic agents in this case osmotic laxatives are examples of drugs that have non-selective effects on the body so in summary some drugs can exert their effects through non-selective interactions with simple chemical and or physical processes without targeting any specific molecule or pathway all right so it's good to be aware of these types of drugs let's now move on and break down the different types of drug targets and how different drugs affect these targets all right now the majority of drugs produce their effects via selective interactions with proteins so they will bind to a protein and alter the function of that protein we refer to the site where a drug binds to exert its action as a molecular Target although protein molecules aren't always the molecular targets of drugs they just make up the majority of them and we can divide these protein targets for drug action into four main groups we have iron channels carrier proteins enzymes and receptors each of these targets play plays an important role in cellular function and can be targeted by drugs to achieve therapeutic effects so again drugs can enhance the activity of a protein inhibited or modify its normal function so let's go through each of these four different types of proteins and use examples of how drugs can act on that type of Target starting with iron channels ion channels are membrane proteins that allow the passage of ions such as sodium potassium and calcium across cell membranes so they are formed by a single protein or a group of proteins that are embedded within the plasma membrane these channels are really important in cellular cell communication between excitable cells so neurons muscles even cells that are involved in secretion so when iron channels are open they're going to create an open pore or passage between the extracellular fluid and the inside of the cell or intracellular fluid and they are characterized by having specificity or selectivity for different types of ions so for example there are channels that are selective for sodium ions potassium ions or calcium ions and the channel name will depend on the selection the different types of ions so a channel that is selective or only allows sodium to pass will be referred to as the sodium Channel and what determines whether an ion can move through the open pore is influenced by the charge of the iron as well as the size of the molecule okay now ion channels can exist in different types of States so they can either be in an open or closed State and these channels are regulated to make sure that they are open or closed in response to different types of physiological signals because cells such as neurons and muscle cells rely on ION channels to create the appropriate signals that allow those cell types to do their job effectively okay so we want to open or close these channels appropriately so this is known as gating of channels or Channel gating so the opening or closing of ion channels is determined by Channel gaming okay iron Channel gating can be regulated by various types of stimuli but we're going to go through two examples voltage-gated channels and ligand-gated channels starting with voltage-k channels these are regulated by changes in the cell's membrane potential so think your neurons and your muscle cells remember that membrane potential refers to the difference in electrical charge between the inside and the outside of the cell resting membrane potential is the voltage difference across the cell membrane when cells are at rest so with voltage-geated channels in this case we have sodium channels these have two gates there's an activation gate and an inactivation gate so the inactivation gate here can be described as a ball and chain-like structure okay so these channels have three states or conformations first it can be closed but capable of opening okay so the inactivation gate here is open because the ball is just hanging free it can be completely open and activated so both gates are open or it can be closed and not capable of opening it's inactivated this is the inactivation state so voltage-gated ion channels will be influenced by whether they're in an open state or a closed State okay so some of these channels will be stimulated to open will be stimulated to open by depolarization or hyperpolarization any changes in the membrane potential determine whether the channel is open or closed alright that's voltage-gated ion channels the other type are ligand gated channels these are also called ionotropic receptors so these are large protein complexes these are iron channels that open directly in response to ligand binding so they are regulated by The Binding of chemical ligands a great example are neurotransmitters that are involved in synaptic transmission once a neurotransmitter binds this will cause the child to change shape and it's going to open up allowing ions from the extracellular fluid to enter so here we have the nicotinic acetylcholine receptor and right now this channel is in its close state so it's not allowing any ions to pass through the channel now when the ligand acetylcholine binds to the channel it will change the confirmation of the channel and earthena and it's going to allow ions in this case sodium ions to flow into the cell and down its concentration gradient okay so these are the two main types of gating channels voltage gain and ligand gating there are also some other types of buying channels that are regulated by other types of physical changes such as stretch sensitive channels and temperature sensitive channels okay so these are just the two main types okay now there are multiple different ways in which drugs can affect the activity of iron channels so drugs that Target iron channels can either block or enhance their activity altering the flow of ions and impacting cellular signaling and communication so some drugs will directly alter ion channels by binding to different sites on the Ion channel modifying the state of the channel okay so a drug can bind to the channel in such a way that it prevents the ions from moving through the channel examples of drugs that Target ion channels include local anesthetics which block sodium channels and reduce pain sensation but let's look at a more specific example by looking at drugs that affect voltage-gated sodium channels if you've seen the action potentials lecture who talked about how important these channels are in generating Action potentials in cells like neurons and muscle cells these sodium channels are usually closed in the resting state and with the neuron depolarizes that triggers the opening of these channels What happens when the Childs are open it's going to allow sodium ions to flow into the cell which allows for the continuation of action potential of the action potential so one example of a drug that directly affects voltage-gated sodium channels is tetradotoxin it's drug directly blocks the channel here so this is a neurotoxin that's found in a range of different Marine creatures and causes inhibition of neurotransmission which leads to a loss of sensation and in higher concentrations paralysis so tetradotoxin blocks these channels which then inhibit Island movement through the channel directly sorry can't pass through ions can't pass through the channel the thing is it doesn't matter whether the channel is in the urban State the inactivated State or the closed State the actions of tetradotoxin are the same so its action is independent of the state of the channel now there are also drugs that affect voltage-gated sodium channels and are dependent on the channel state for their action an example is lignocaine which is a type of anesthesia that works by binding to open or recently open channels in the nerves so when neurons are firing frequently there are more open or inactivated channels or in active channels for lignicane to bind to in those areas this is important because it allows for more targeted anesthesia in these areas with more nerve activity which is especially useful since Sensory neurons increase their firing rate with the intensity of the stimuli causing them to fire so lignocaine's interactions with these channels is used dependent meaning it is more effective in areas with higher nerve activity okay so essentially there are different ways drugs can interact with ion channels either directly such as with tetrodotoxin or dependent on their Channel State like lignitine all right that's ion channels let's now move on to the second type of protein Target for drug action which is another type of transport protein carrier proteins carrier proteins are membrane proteins that transport molecules across cell membranes here's the thing they don't form an open Channel or pore between the inside and outside of the cell what carrier proteins do is they take different conformation shape okay and shuttle the molecule from one side to the other this process involves a series of changes in the structure of the carrier protein that influence its orientation towards the inside or outside of the cell as well as the ability of different molecules to bind to it so specifically when a soil molecule needs to be transported across the membrane it binds to the carrier protein causing a conformational change so here we have the molecule it's cured as molecule that needs to be transported and the gate to the inside of the cell is closed but open to the outside of the cell and so this is going to flip okay this flips the carrier protein so that it is no longer open to the outside of the cell but now open to the inside of the cell so the gate is close to the outside so there's a conformational change here okay the shape is changing so this change in conformation allows the solid molecule to move across the membrane and then eventually dissociating from the carrier protein inside the cell it's pretty cool right now one key feature of carrier proteins is that they're never open to both sides of the membrane at the same time this is because the solid molecule must bind to a specific site on the protein channel to be transported and this also means that the carrier proteins can be subject to competition and potential saturation of the transport mechanism okay so the binding Affinity of the solute to the carrier protein is also affected by conformational changes in that protein structure this means that the ability of different molecules to bind to a specific carrier protein can vary all right now carrier proteins can be classified in different ways one method involves characterizing them by the type of molecule they transport such as sodium glucose or potassium and there are also several types of carrier proteins including uniport Transporters that can only transport a single molecule and co-transporters that can carry multiple types of molecules simultaneously or at the same time such as sodium glucose protransporters or sodium potassium co-transporters okay if they're co-transporters move the molecules in the same direction across the membrane they are referred to as simple carriers however if the transport protein moves molecules in different directions they are known as antipod carriers so that's one method another method of characterizing carrier proteins is based on the energy source that powers the transport passive transport or facilitated diffusion occurs when molecules move down their concentration gradient without the need for external energy it doesn't require any energy whereas active transport involves the movement of molecules against their concentration gradient which requires external energy such as ATP okay so now that we've established what carrier proteins are let's look at some examples let's look at how drugs can influence this process can influence carrier proteins so drugs that Target carrier proteins can interfere with their ability to transport molecules altering cellular metabolism and function we're still looking at neurotransmission here so we have the presynaptic terminal and the person optic cell and we have a per synaptic receptor right here and what a substance binds you will produce a response in the per synaptic cell okay so remember what happens when an action potential reaches the axon terminal it's going to stimulate the voltage-gated calcium channels to open and calcium ions are going to flow into the synaptic knob where calcium triggers the release of neurotransmitters from the synaptic vesicles here which contain dopamine serotonin and noradrenaline so here we have neurotransmitters being released at the synapse where they can interact with a receptors to produce a response but what we're truly focused on here is the reuptake process these neurotransmitters are terminated their actions are terminated when they are removed from the synapse okay so generally the removal of the neurotransmitter occurs via reuptake into the presynaptic neuron via a carrier protein through the process of facilitated diffusion okay so reuptake is when the neurotransmitters are taken back up into the presynaptic neuron after they have been released into the synapse now why is this process important why are we talking about this because reuptake helps helps the regulation it helps to regulate the duration and strength of neuronal signaling it's important to the overall functioning of the nervous system and there are several different drugs that can interfere with this process and they do Serve by blocking the carrier proteins okay because if you block the carrier proteins what's going to happen you will get less of the neurotransmitter that gets taken back up into the presynaptic neuron and what happens okay so when this happens what do we do it means you've got more neurotransmitter present in the synapse and therefore you're going to enhance the actions of that neurotransmitter because remember the actions of the neurotransmitter are early terminated when they are removed from the synapse so if we're blocking the re-uptake protein okay this carrier protein here we're going to be leaving neurotransmitters in the synapse that therefore enhancing their activity so let's go through two examples including cocaine and Fluoxetine so first up cocaine so what cocaine does is it blocks the carrier proteins that are responsible for neurotransmitters such as dopamine and norepinephrine so then it has a stimulatory effect on those neurotransmitters because these transmitters are going to stay in the synapse for longer causing Euphoria and all the other effects that cocaine has so there's going to be a buildup of these neurotransmitters in the synapse okay so that's cocaine on the other hand fluoxetine is an example of a drug that is more selective for individual carrier protein mechanisms what fluoxetine does is blocks the carrier protein that is responsible for the reuptake of Serotonin into the nervous system this is an example of a selective serotonin react take with okay which blocks the reuptake of Serotonin and increases its availability these drugs are one of the most commonly used in the treatment of depression okay so these are the different ways in which drugs can interfere with carrier proteins to influence the actions of neurotransmitters let's now move on to the next type of drug targets enzymes so recall that enzymes are biological catalysts they speed up a reaction without being consumed other reaction and most enzymes are proteins enzymes are important for a whole range of biological processes their activity depends on their protein conformation including primary secondary tertiary and quaternary protein structures if an enzyme is denatured it's catalytic activity is gone okay so drugs that Target enzymes can either enhance or inhibit their activity altering cellular metabolism neurotransmission and function let's go through an example of a drug called near stigma that inhibits an enzyme involved in neurotransmission so you may have heard of acetylcholine okay so acetylcholine is a neurotransmitter that's important in the peripheral and central nervous system and synthesize from acetyl-coa and choline catalyzed by choline acetyl transferase now the actions of acetylcholine are terminated when acetylcholine is broken down similar to what we've just spoken about and it's broken down by an enzyme called acetylcholinesterase that is found in nerve terminals where acetylcholine is released okay so when acetylcholine is released it can then diffuse across the synapse and bind to per synaptic receptor proteins so then this acetylcholine receptor opens up allowing ions to flow inside so going back to acetylcholinesterase it breaks down the acetylcholine into choline and acetate in activating that neurotransmitter because the actions of a neurotransmitter is terminated when it's removed from the synapse so what we're doing here is we're going to break it down to choline and acetate there are several different drugs that can Target inhibit this acetylcholinesterase okay so different drugs can inhibit acetylcholinesterase and one example of a drug that inhibits acetylcholinesterase in a competitive or reversible manner is near stigma okay so neostigmine binds to and inhibits acetylcholinesterase so then what happens when we inhibit the activity of this enzyme well now we can't break down acetylcholine and so we're going to end up with increased levels of acetylcholine at the synapse so neostigmine is a drug that is involved in the treatment of myasthenia gravis which is our neuromuscular disease that's characterized by a failure of transmission at the neuromuscular Junction okay and the main neurotransmitter at the junction is acetylcholine so if we step back and think about that for a second by preventing the breakdown of acetylcholine we're going to increase the levels of acetylcholine at the neuromuscular Junction and what's this going to do it's going to enhance neuromuscular transmission okay so that's near stigma and we mentioned that this drug can bind to and inhibit this enzyme reversibly but there are also drugs that do this irreversibly which means we can't take it back okay and there's a name for this family of molecules that irreversibly inhibits this enzyme here they are known as organophosphates all right so this is an example of how enzymes can be the cause of drug action for either enhancing or inhibiting the activity altering its function okay the last type we're going to look at are receptors so these bad boys recognize and respond to the different types of chemical messages that our body uses to communicate they bind to specific signaling molecules such as hormones neurotransmitters and cytokines and transmit signals into cells so the effect of neurotransmitters hormones and other chemical mediators are controlled by receptors so drugs that Target receptors again can either enhance or block their activity altering cellular signaling and function and one common mechanism for influencing a recipe is through an activating drug which is known as an Agonist an Agonist is a drug that binds to and activates a receptor we're going to talk about this in more detail in further pharmacodynamic structure okay but just know an Agonist is a drug that binds to and activates a receptor whereas an antagonist is a drug that binds to the receptor but does not cause activation it combines to it but it doesn't activate it so when an Agonist binds to a receptor it's going to activate a signaling mechanism within the cell and which have a signaling mechanism is activated will determine the cellulite effects examples of drugs that Target receptors include beta Agonist which activate beta adrenergic receptors and increase heart rate and Airway dilation and we also have antihistamines which block histamine receptors and reduce allergic symptoms we'll break down the four main types of receptors in another lecture but for now understand that receptors are a very diverse group of proteins and can mediate a whole range of different types of effects in the body from quick responses like neurotransmission to much slower processes that are related to growth and development okay all right so we've covered a lot in this lecture so to summarize it okay drugs can affect the four main types of molecular targets for drug action we have iron channels carrier proteins enzymes and receptors by either enhancing or inhibiting their activity or altering cellular signaling and function to achieve therapeutic effects thank you for watching this video make sure you subscribe to EKG science so you don't miss a single lecture and remember subtract complexity and slow down to study the next lecture simply click the next video or you can view the entire playlist