Ok, in this video we're going to start talking about antibiotics. So if you are following along with cards in the dark green section which starts on card 127, but before we get into specific antibiotics, I want to go over some key concepts regarding antibiotic therapy. So antibiotics can be either broad spectrum or narrow spectrum. If they are broad spectrum, then they are effective against a wide variety of bacteria; if they are narrow spectrum, then they may only be effective against a few strains of bacteria. So it's better to go with the narrow spectrum if we can because a broad spectrum antibiotic can really do a lot of damage to the naturally occurring microRNAs. So, good and bacteria may get killed with that broad spectrum antibiotics. And then the other thing I want to talk about here is the difference between bactericidal antibiotics and bacteriostatic antibiotics. So bactericidal antibiotics are going to kill bacteria. They are lethal to bacteria whereas the bacteriostatic antibiotics slow the growth of the bacteria and then they let your immune system kind of finish the job. So if you have an immunosuppressed patient whose immune system isn’t fully functioning, then something bacteriostatic is probably not going to be the best because it really relies on the immune system to finish the job off. They will likely need something bactericidal. In terms of starting antibiotics, you always want to take a cultural sensitivity prior to initiating an antibiotic therapy. So when we take a sample, maybe a sputum sample, it could be a wound sample or even a blood sample, we take the sample we grow it out to see what the cause of agent is, like what the bacteria is, is it causing the infection. And then we do a sensitivity which determines which antibiotics can be used to kill or so the growth of that bacteria. So which antibiotic is going to be effective against that bacteria. That is the sensitivity part of a cultural sensitivity.
Sometimes antibiotics are giving the patients prophylactically. So for example, a patient who has an artificial joint, like my mom who has an artificial knee, she actually has an artificial shoulder now, when we have these artificial joint then it's absolutely the right thing to do that, to take an antibiotic prior to any dental work or any kind of surgical procedure to prevent the risk of infection in that artificial joint. And then lastly, it's really important for you to tell your patient that they need to complete the entire course of antibiotic as prescribed. They should not stop in the middle when they start feeling better or anything like that. They need to complete the entire course in order to prevent antibiotic resistance in the future.
OK so now that we got some of these key concepts out of the way, I'm going to start talking about some antibiotics that affect the cell wall.
So the first one is probably one that you've heard of, the penicillin. So penicillin is more of a narrow spectrum, penicillin. And then amoxicillin is more of a broad spectrum penicillin agent. Another one that you'll see in the hospital at least i see very frequently is piperacillin-tazobactrum. So that is another penicillin that can be used. So if you would use these medications against bacterial infections, they weaken the bacterial cell wall, causing cell’s death. Side effects can include GI upset and then allergy is the big important one you need to know for penicillins. So this can be dyspnea and rash, then difficulty breathing, rash, ……. These medications can also cause renal toxicity. In terms of key points you never want to administer a penicillin to a patient who has a history of allergies to either penicillin or cephalosporin and then you're definitely going to monitor the patient for signs and symptoms of an allergic response.
OK, the next one that affects the cell wall are cephalosporins. So there's a bunch of different medications of that kind that fall under this umbrella of cephalosporins. So this includes cephalexin, cefazolin, and ceftriaxone. You know they all start with that cef- in the beginning. So again, these are used against bacterial infection. They weaken the bacterial cell wall, causing cell death. In terms of side effects, we going to have some of the same side effects, so GI upset is one, allergy is another, and then super-infections are also someone comment. So things like C. diff or a yeast infection can occur after therapy. Key points again, you do not want to administer medications to a patient who either has a history of allergies to either penicillin or to cephalosporins. And then your patient should not consumer alcohol during therapy and it's advisable that they take this medicine with food.
OK and then the next class are carbapenems. So this will include imipenem, cilastatin, kind of abbreviated and if you have my card just on there. Indications. You would use this medication for serious bacterial infection. This is a broad spectrum antibiotic. It destroys the bacteria cell wall, causing cell death. In terms of side effects, we have GI upset, rash, and then possible super-infections such as C. diff or a yeast infection. Key points again. If a patient is allergic to penicillin or to cephalosporins, then they may also have a reaction to carbapenems. So you need to be cautious with that.
OK and then the last one I am gonna want to go over in this video is a… an antibiotic that is used for very serious infections again. So this is vancomycin, very common antibiotic that you will see in the hospital. So it's used for serious infections and antibiotic associated C. diff infections. Mode of action. It destroys the bacterial cell wall, causing cell death just like all these other ones we have been talking about. Side effects are super important to know for vancomycin. So the two big ones that you absolutely have to know if your test, include ototoxicity and renal toxicity, or kidney damage. Other side effects can include infusion reactions as well as phlebitis. Very hard on the vein. So we often… if the patient’s to be on vancomycin for a while, we will put them in a PICC line and administer vancomycin through that PICC line. Key points. We're gonna wanna monitor vancomycin trough levels and possibly peak levels when the patient starts on the therapy. If you recall towards the beginning of this whole video series we talked about therapeutic index and risk of toxicity, so there is a definite high risk of toxicity with vancomycin, because it has a very narrow therapeutic range. We need to get over the minimum effect of concentration. We need to stay under the toxic levels. So we need to hit this very specific range in terms of blood levels. So that's why your patient will have numerous …… to get the dose just right. And then we also need to really keep an eye on their creatinine levels because of the risk of kidney toxicity. So the way I remember the key side effects of this. Vancomycin is a stretch of that van. So I think of someone listening to music super-loud in their van, like way to out and it causes ototoxicity. They are also not drinking any fluid so they are super dehydrated and that ends up with kidney toxicity. So I just imagine someone driving with the super-loud music and dehydrated and then their kidney’s suffering because of that. So that helps to remember ear damage, kidney damage.
OK and that is it for this video so we will pick it up with more antibiotics in my next year.
Questions 1. A 6-year-old boy presents to his pediatrician for follow-up of recurrent hay fever and asthma. He usually has two to three attacks per week. For symptom control, he uses an albuterol inhaler, but his parents would like to try something more. They would like him to take something that would lessen the amount of attacks he has. Although corticosteroids would probably work best for prophylaxis, they are contraindicated in children. Which of the following drugs would decrease the amount of asthma attacks by preventing an arachidonic acid derivative from binding to its receptor?
A. Aspirin
B. Celecoxib
C. Ipratropium
D. Montelukast
E. Zileuton
2. A 15-year-old female presents to her primary care physician complaining of runny nose and itchy eyes. She said that she first had these symptoms during the spring a few years ago, but each year, they have been bothering her more. You know there are multiple ways to interfere with the signaling that is causing her symptoms. Which of the following drugs would prevent the release of the main chemical mediator in her case?
A. Cromolyn sodium
B. Diphenhydramine
C. Ranitidine
D. Loratadine
E. Theophylline
Answers 1. The answer is D: Montelukast. Arachidonic acid is the precursor for the eicosanoids such as prostaglandins and leukotrienes. First, phospholipase A2 cleaves cell membrane phospholipids to release arachidonic acid. Arachidonic acid can then be converted into prostaglandins by cyclooxygenase (inhibited by aspirin and celecoxib) or into leukotrienes by lipoxygenase (inhibited by zileuton). Prostaglandins are drivers of inflammation. Leukotrienes cause bronchoconstriction, mucus production, and increased vessel permeability leading to the symptoms of asthma. Montelukast works by blocking leukotriene binding to its receptor. Ipratropium and albuterol work on autonomic nervous system receptors rather than on the arachidonic acid pathways. Ipratropium is a parasympathetic antagonist, whereas albuterol is a sympathetic agonist— both work to relax bronchial smooth muscle and decrease secretions. 2. The answer is A: Cromolyn sodium. This patient has a classic history of allergic rhinitis, commonly called hay fever. Symptoms are caused by itching and vasodilation from histamine binding to H1 receptors. The histamine is released from mast cells as they degranulate, which is caused by antigen linking two IgE molecules attached to their cell membrane. Mast cells must be “sensitized” before they can react this way, which occurs when IgE made by plasma cells attaches to receptors on mast cell membranes. Mast cell stabilizers such as cromolyn sodium prevent the release of histamine.
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