14.03 Sympathomimetics (Alpha (Clonodine) & Beta (Albuterol) Agonists)

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Sympathomimetic drugs. Also called, known as adrenergic agonist medication. People say adrenergic drugs, there are different words that people use for this ANS drugs. And I highly recommend that you watch the autonomic nervous system video before you watch this one because it will help you to understand all the different receptors in the sympathetic nervous system and parasympathetic nervous system has and what are the physiological responses when you activate or if there is a medication that goes and binds to the receptor and activate them. In this video, we gonna learn about the sympathomimetic drugs based in, I have divided these drugs in a 3 section to Mixed agonist. And in this medication, in this section, we’ll look at the medication that works on more than 1 sympathetic nervous system receptors. Alpha agonist, we’ll, in that one, take a look the medication that particularly works for on the alpha 1 and then alpha 2. And we’ll take a look at into this lastly the Beta agonist, especially, we’ll go over Beta 2 agonist medication that goes and binds to this beta 2 receptors in our body.So, let’s take a look in the Mixed Agonist. The first drugs we gonna take a look at into is the Epinephrine. And this is really important drug, not only as a nurse that you need to know in, for NCLEX, but this is really important drug if you gonna work in an intensive care unit after you become a nurse. ‘Cause you’ll be using this drugs a lot of time as a drips and also some mostly in code blues as well. Mostly, not mostly, but all the time, I would say. So, these drugs work on 3 different receptors in our body. The Alpha 1, Beta 1 and Beta 2. And these are the sympathetic nervous system receptors. When these drugs goes and binds to alpha 1 receptors in our body, what it does, it causes the vasoconstriction, and it increases the drainage of aqueous humor and decreases the intraocular pressure because that aqueous humor gets drainage out of the eye, that will decrease the intraocular pressure. Now, when this drug goes and binds to the beta 1, it has a positive inotropic and chronotropic. So, it will increase the force of contraction rate, I mean, heart rate. Force of contraction of heart, heart rate and eventually it will, this will increase the cardiac output. And finally, this medication also works as a, on the beta 2 receptors in our body which will relax the bronchial smooth muscles and vascular smooth muscles. So, what it will do, it will cause the bronchial smooth muscle relaxation, so the trachea will enlarge and there will be, air movement will be easy throughout the lung. And when it relaxes the vascular smooth muscles, it’s gonna cause the vasodilation. Now, there’s a thing to remember. The beta 2 receptor are, like if you have watched the autonomic nervous system video, the beta 2 receptors are mainly located into the bronchial smooth muscles. There are only few from our present in vascular smooth muscles. So, even though it causes the vasodilation, vasodilation is not a significant. So, the blood pressure does not decrease significantly. And this beta 2 vasodilation will be over shadowed by alpha 1 because when the alpha 1 mostly present in the vascular smooth muscle, it will cause the vasoconstriction, so the blood pressure will go up ‘cause this effect is gonna be more compared to this beta 2 vasodilation. Because there are not too many receptors, there are not too many beta 2 receptor present on the vessels. So, if you, now we understood the mechanism of action and what receptor it binds to and what is the physiological response of this epinephrine drug.Let’s take a look into the indication like in which disease process we can use this drug and what are the side effects. So, obviously, definitely, in shock, we can use this medication. And the reason we use this in shock is usually like either if it is a hypovolemic shock, if it is a septic shock, or cardiogenic shock, or neurogenic shock, mostly happens is the decrease in blood pressure. And, we will use this drug as a IV drip to increases the blood pressure and also to increase the force, and the force of the contraction of the heart and also the rate. So, the cardiac output will increase as well. So, all the vitals organ in our body get perfused. Since this medication also relaxes the bronchial smooth muscles, we can use this medication for the bronchospasm. Now, what if we give this medication for the bronchospasm IV? Well, it’s gonna definitely have a effect on different organs on top of this bronchial smooth muscles. So, that is the reason, whenever there’s a bronchospasm, we give the racemic mixture of epinephrine. Now, when we give the racemic mixture, what I mean by that, is this epinephrine will be diluted into the normal saline and the concentration of the epinephrine will be so low and will give this one as a breathing treatment. So, we’ll give as a aerosols or inhalers, kinda like that stuff. So, have a local effect in the bronchial muscles only, not throughout the body. So, that’s kinda interesting thing too. And also, we use this medication for glaucoma, as well as it decreases the intraocular pressure. Since this one causes the vasoconstriction, so, what if we give if this medication locally to a certain area of the body? Let’s say, if we need to give a local anesthetic medication. They usually give this epinephrine with the local anesthetic. And the reason they do, it’s this one will cause the local vasoconstriction . Now, it will cause the vasoconstriction, so the medication, the anesthetic medication, the local anesthetic that we give will stay in the area for a longer time compared to, compared when we give it on without this epinephrine. So, they usually use this medication with anesthetic. So, the anesthetic medication effect will stay longer than usual. And also, this medication also we use this one for hypotension since it causes the potent vasoconstriction.Let’s take a look at into the side effects as well. Now, whenever we think about the side effects of any kind of anes drugs, is usually the physiological effect this medication has on our body that we do not want. So, for example, for this epinephrine, well, they do not want any kind of GI effect. Let’s say their blood pressure is going down and we want to give this medication to increase the blood pressure. However, if you look at into the sympathetic nervous system, there are many other effects sympathetic nervous system has on our different body parts like the GI. Now, we don’t want GI effect. So, but, it will have GI effect. So, it can cause nausea, vomiting and kinda like that stuff as a side effects. Like a, sometime it can increase the heart rate really high. So, the patient may feel the heart palpitation, it can cause the cardiac arrhythmia as well, sweating and also the headache. Now, since, this also this medication is used for hypotension, but if we give it too much, it can cause a hypertension. And when you, like, when you will start working in the intensive care unit after you’re done with the nursing, you may see they are many patient, like one patient will react differently than other patients especially for this IV vasopressors, so like this epinephrine, norepinephrine, dopamine, dobutamine, all kind of medication that we use in critical care. All the patient will react differently. So, you have to be really careful when you’re titrating this drug in order to achieve the goal blood pressure.Okay. The next medication, we gonna take a look into the norepinephrine. Now, if you remember, the epinephrine has a effect in alpha 1, beta 1 and beta 2. However, this drug does not have effect on beta 2. These drugs work on alpha 1 and beta 1. When it works on the alpha 1, it causes the vasoconstriction, and decreases the intraocular pressure. In beta 1, positive inotropic and chronotropic gonna increase the force of contraction and the rate of contraction in the heart. And eventually, it gonna increases the cardiac output. So, what are the indication? We can use this for the shock. We talked in the previous slide as well that in the shock, it causes the like hypotension, like a vasodilation throughout the body. In most of the shock, then we can use this medication for the, to increase the blood pressure. So, all the vitals organs can get perfused. Hypotension and Cardiac Arrest. So, now, and also, the side effects is gonna be the same as we talked in the previous slide. It’s like all these arrhythmia, hypertension, heart palpitation, headache, nausea, vomiting and sweating.Now, the next drug is dopamine. This is really interesting drug and important drug to know, falls into the mixed agonist category. Now, this medication is dose dependent. So, dopamine, when you give this medication 2 to 5 mcg/kg/min, it works only on dopamine receptors. And what does this dopamine receptor does? It dilates the renal and coronary and splachnic vessels. And when it does, the kidney will get more blood flow. Since the vasodilation will decrease (the blood flow), the pressure in the kidneys. So, that’s why we use this medication sometime in the cardiogenic shock. So, the kidney can get the enough blood perfusion. Now, in the beta 1, when we give this medication from 5 to 10 mcg/kg/min concentration, it will work on beta 1. And when it works on the beta 1, we’ll have positive inotropic and chronotropic effect which will increase the heart rate and the cardiac output. I mean, the force of contraction as well. And that will increase the cardiac output. However, if we give dose greater than 10 mcg/kg/min, it’s gonna cause the potent vasoconstriction, it gonna increases the blood pressure. So, this drug is kinda is totally dependent on how much dose you give to a patient. Now, it will have that kind of physiological effect accordingly. So, that’s why there are like a different uses for this medication. We can use this medication to increase the blood pressure, if we give dose higher than 10 mcg/kg/min. We can increase the blood flow to the kidney if we give dose between 2 to 5 mcg/kg/min, and can use this medication for the cardiogenic shock if you use this medication in this concentration because it will increase the cardiac output and the, also will increase the heart rate and also the force of contraction. So, these drugs are kinda little bit interesting also and tricky at the same time.The next drug is dobutamine. Now, dobutamine works on beta 1 and beta 2. This medication does not have any effect on dopamine receptors because this medication is kinda like people always get confused with dopamine ‘cause they kinda like look like the same, they kinda like sounds like the same, but there’s a difference. Dobutamine does not work on dopamine receptors. However, this is kinda good drug than dopamine. If we have to just, if you’re just giving it for the congestive heart failure or cardiogenic shock, because this one particularly works on beta 1. And that will have a positive inotopic and chronotropic effect, then increase the heart rate and cardiac output as well. Now, when it works on the beta 2, I told you, like there are not many beta 2 receptors on vessels, blood vessels, however, there are some. So, it can cause the vasodilation. Now, when it increases the heart rate, and force of contraction plus decreases the systemic vascular resistance, which is blood pressure, by doing this vasodilation, heart workload will be decreased. ‘Cause heart won’t have to pump really hard in order to get the blood out of the heart because there’s not much systemic vascular resistance. So, this medication is really really good for congestive heart failure and also for the cardiogenic shock and usually, this medication is also used as IV medication, IV drips in critical care areas. And this is not a dose dependent drugs as well. This is not a dose dependent drugs like dopamine.Now, the next category we gonna take a look at into the Alpha 1 agonist. Now, there’s a main 4 drugs fall into this category. Phenylephrine, Methoxamine, Metaraminol and Midodrine. And when this medication goes and binds to alpha 1 receptors in our vessels, it causes the potent vasoconstriction. That’s why we can use this medication in a shock where we have to increase the blood pressure, to maintain the blood pressure during anesthesia, because if a patient is under anesthesia effect, they get the hypotension, so we can use this one. And also, for the orthostatic hypotension. I have seen Midodrine used for orthostatic hypotension often. Now, if we use this medication as a nasal spray, it can decreases the nasal congestion. Because there are small blood vessels in our nose, in nasal area, what happens during the nasal congestion, because there’s so much secretion, either due to the allergy, or any kind of, some kind of reason. That they secretes the more, more secretions in our nose and that causes the nasal congestion. They are dilated during the nasal congestion. So, when we give this medication as the nasal spray, it will cause the potent vasoconstriction in our nasal area. And what it will do, it will decrease the all secretion in our nose. So, that’s why we can use this medication for nasal congestion as well. So, if you’re using this medication as a nasal spray, it may not have a systemic effect but in some cases, if people use it more than the recommended, it can have really bad systemic effect. Like it can cause the high blood pressure, heart rate’s gonna go up, and so forth. Now, the side effects, is like, as we talked like the side effects of this medication are the non-wanted physiological effect of the medication that we gonna have. So, like you know, like a sympathetic nervous system, it get activated, you can have anxiety, restless, like all kind of stuff. You can have EKG change, blurred vision, fatigue, can go to depression, it can cause the cardiac arrhythmia, and since it decrease in urine output, and GI system is gonna be inhibited, so, it can cause the anorexia as well.Okay. Alpha 2 agonist. This is also really good interesting category to learn. Now, since if you have watched the autonomic nervous system video, whenever we excite this alpha 2 receptor, which are located centrally. Remember, these receptors are located centrally. When we excite these receptors, if we give a medication that goes and binds to this receptors, it’s gonna decrease sympathetic nervous system, okay? So, it’s gonna do the actually opposite by exciting this receptor, exciting this sympathetic nervous receptor which are located centrally in brain, it’s gonna decreases the sympathetic nervous system effect peripherally. So, this medication can cause the, will cause the vasodilation since it gonna decreases the sympathetic nervous system effect peripherally. Now, the medication that falls into this category is Clonidine, Methyldopa, and this is really an interesting drug too, Dexmedetomidine. And I’ll get back to that one really quick once we are done with this. So, it causes the vasodilation. So, this medication can be used for high blood pressure, and this medication, one of them is used for the sedation and that is Dexmedetomidine. It took me a long time to pronounce that. Alright. It’s also called the Precedex, that’s the trade name. Precedex. And usually used as a IV drips in a critical area for the sedation. Because this medication goes and binds to the alpha 2 receptor located in the brain and causes the sedation. And, if a patient on this medication, you have to be really really careful because I have seen many patient, when we put this medication on for sedation, their blood pressure drops significantly. Like if they’re running like, let’s say, 160/80. They will drop to like 90/60 like in 15/20 minutes if they are so labile to this medication. So, sometime, if you put the patient on this medication, you may need another vasopressor like a phenylephrine which is alpha 1 agonist and as we talked previously, like epinephrine or norepinephrine vasopressor in order to make sure we maintain the blood enough blood pressure. So, that’s the medication, this kinda really interesting to know that we use it in critical care more often for sedation. So, the side effects, this medication can cause drowsiness, dizziness, dry mouth. And if we stop this medication, like if a patient on this medication, to decrease their blood pressure, for some reason, if they stop this medication suddenly, they can have a rebound hypertension and the blood pressure can go really really up. So, this is one of the side effects. Precaution. You don’t really wanna give this medication for a patient who has a recent MI, cerebral vascular accident or stroke, Diabetes Mellitus, because, you know, like sympathetic nervous system works on liver, it can increase the glucose production. It can cause the increase in blood glucose level, okay? So, you really wanna be either careful, or avoid this medication if a patient has a Diabetes Mellitus. And renal and liver disease, if a patient has, you wanna avoid this medication as well.Alright. The next one and the last one, Beta 2 Agonist. The medication that falls under this category are Albuterol, Formoterol, Isoproterenol, Metoproterenol, Ritodine, Salmeterol and Terbutaline. What is does, as we remember, from autonomic nervous system video, that these receptors are present in bronchial smooth muscles, and uterine smooth muscles. So, when we give this medication, and activates this beta 2 receptors present here, bronchial and uterine smooth muscle is gonna dilate, both of these smooth muscles. So, and it will have the physiological effect. If they do these things, we can use this medication for asthma, we can use this to treat shock and ventricular arrhythmia, and this is for only Isoproterenol, because it has beta 1 effect as well. The other medication in this category has only beta 2, so, like this one is beta 2, only beta 2, this is beta 2 as well, this beta 2, beta 2, these are all beta 2 except this Isoproterenol. Now, there’s a Ritodrine (Sorry, I missed out that one. It’s not Ritodrine), it’s Ritodine. That medication also used to slow the uterine contraction in a pregnant woman. So, that’s the only medication has been used for right now, currently. And these medications are kinda interesting to know. If you know Albuterol, it’s used for like asthma because these are like really short acting. Like, it works in minutes. So, you wanna give this medication for like status (Sorry, not status), in asthma, when there are respiratory system is compromised and they can’t really breathe. This medication works really fast compared to the other medication in these categories. The side effects as usual, there are all other physiological effect that we do not want is restless, anxiety and tremor, headache, tachycardia, it can cause really bad heart pain; angina. And there’s also another thing to like this medication only works on beta 2, but it can have another physiological effect. So, usually, this medication, if you’re giving for asthma, we can give it as a inhaler or nebulizer, like that, but still, it’s gonna have some absorbance systematically. Systemic Absorption. So, that’s why it can cause these side effects. It can cause MI, heart palpitations, and GI system unwanted effect like nausea, vomiting, anorexia. It can cause really bad pupil dilation and muscle cramps.Okay, so, that was it about in sympathomimetic drugs. I hope you understand really well. If you have any questions, let us know or e-mail us. Thanks for watching.
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