Hey everyone, this lesson is on the macrolide antibiotics. The macrolide antibiotics all end in the suffix thromycin. Remember that, thromycin.
So examples of the macrolides include erythromycin, azithromycin, and clarithromycin. So erythromycin was the first original macrolide antibiotic and the other azithromycin and clarithromycin were derivatives of the original erythromycin. So again, remember that it is thromycin at the end of a macrolide, not mycin, but thromycin. All the macrolides have good absorption, but they do not cross the blood-brain barrier. And clarithromycin and azithromycin are absorbed better orally.
So what are some of the bacterial targets of macrolides? The macrolides are good at combating gram-positive aerobes like strep pneumoniae and methicillin-sensitive staphylococcus aureus or MSSA. They're also good in treating carini bacterium as well and diphtheria.
So in general, macrolides are good against gram-positive aerobes except enterococcus. So again, good for gram-positive coverage except for enterococcus. They're also good for gram-negative A-robes as well. They can treat morexella catarrhalis and H. influenza.
And they're also good for Legionella, Bordetella pertussis, Gonorrhea, Campylobacter, and Seminella typhi. Another one that they're also good in treating is Helicobacter pylori. But they are not useful against Enterobacteriaceae.
So Again, macrolides are good for gram-positive coverage except for enterococcus, and they're good for gram-negative aerobes except for enterobacteriaceae. So the infections that macrolides can treat include respiratory infections, so they're good for treating particular types of pneumonia, like azithromycin, so community-acquired pneumonias generally treated with azithromycin, and also... generally a third generation cephalosporin like ceftriaxone is also used.
They're also good for treating pertussis and bacterial bronchitis. They're also good for treating STIs like gonorrhea. So azithromycin is actually the treatment we use for gonorrhea. They're also good for treating helicobacter pylori infections. They're part of the triple therapy for H.
pylori infections. Cholerythromycin is the one we use specifically for H. pylori. And they're also good for treating typhoid fever because they have activity against seminella typhi.
So in general, the macrolides all have similar targets, but because erythromycin was the oldest one, there has been some modifications on its original structure to produce azithromycin and clarithromycin, which have increased spectrum of targets. So as we move from erythromycin to azithromycin to clarithromycin, the spectrum of activity against bacteria has increased. So how do macrolides work?
What is their mechanism of action? They are all bacteriostatic and they inhibit protein synthesis through an inhibition of bacterial 50S ribosomal subunits. So they have the same mechanism of action as clindamycin.
So what they do is, again, they actually bind to and inhibit the bacterial 50S ribosomal subunit. leading to decreased protein synthesis and bacteriostasis. So there are particular risks for using macrolide. Some of the side effects of macrolide use include hepatotoxicity.
This is one of the big side effects we want to be aware of. So in some instances, patients can have hepatitis, cholestatic jaundice, hepatic necrosis, and failure from macrolide use. So we want to...
avoid using macrolides in patients with hepatic dysfunction. So they are contraindicated in patients with hepatic dysfunction. Some other adverse reactions to macrolides includes GI toxicity, which causes nausea and diarrhea, and it does this through activating motillin receptors.
Macrolides can also cause QT prolongation, so we want to avoid using macrolides with other QT prolonging drugs. And macrolides are associated with other adverse reactions, including anaphylaxis. Stevens-Johnson syndrome, DRESS or drug reaction with eosinophilia and systemic symptoms, and pseudomembranous colitis, so a C.
diff infection. And there are particular instances where it's been shown that there are specific drug reactions to clarithromycin in particular. So there has been evidence to show that there are drug reactions between clarithromycin and colchicine, so we want to avoid using these together.
There's also been some evidence of drug reactions between clarithromycin and calcium channel blockers, which have been shown to increase the risk. of acute kidney injury. So we want to avoid chloroethromycin in patients using calcium channel blockers. So anyways, guys, I hope you found this lesson helpful. That was a lesson on macrolides.
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