Macrolides are a class of antibiotics most helpful against gram-positive bacteria like Streptococcal, Corynebacterium diphtheria (which causes diphtheria), and Staphylococcal infections.
However, it is not effective against the gram-positive group of bacteria called Enterococcus.
Macrolides can also target some gram-negative bacteria like Salmonella, Chlamydia, H. pylori, Legionella, Gonorrhea, and H. influenza (causes epiglottis).
Therefore, this class is great at treating ear infections like otitis media (middle ear), upper (throat/sinus infections) and lower respiratory infections (like pneumonia and legionnaires), GI and GU infections, and sexually transmitted infections.
Before reviewing this material don’t forget to watch the Macrolide lecture and to take the Macrolide quiz afterwards.
What medications are Macrolides?
FACE
- Fidaxomicin (used to treat Clostridioides difficile (c.diff) *new to the group
- Azithromycin
- Clarithromycin
- Erythromycin
This group ends with thromycin or micin. However, be very careful when you analyze the endings of the generic names because Aminoglycosides have similar endings as well.
How are they administered?
Oral or parenteral (mainly IV)
Macrolides Mechanism of Action?
Macrolides are known to be overall bacteriostatic, which means they inhibit the growth/reproduction of the bacteria. They are able to do this by inhibiting protein synthesis.
Proteins are a very important structure for the normal function and existence of a cell. A bacterium’s cell needs to make healthy proteins in order to continue living. Therefore, if we can target the bacteria’s process for making proteins we can prevent it from growing.
The particular structure within the bacteria that makes proteins is called the ribosome. A ribosome is made up of two subunits that work together to stack amino acids into chains called polypeptide chains, hence creating the proteins.
These subunits are known as 30S and 50S. Macrolides target the larger of the two subunits called 50S. To help you remember which part of the ribosome Macrolides target, remember that the word Macro means large/big and the subunit that is targeted in the large one (50S).
Now, by targeting this subunit it prevents proper translocation of messenger RNA and transfer RNA within the ribosome. Therefore, mRNA and tRNA can’t move properly through the ribosome to help create proteins. This will help prevent the bacteria from thriving and growing. Therefore, they are bacteriostatic.
Nursing Considerations for Macrolides
Before administering check allergies and obtain any cultures needed beforehand. As a side note, you will encounter patients who are allergic to Penicillin. Macrolides are sometimes prescribed to these patients as a better alternative.
During and after administration monitor for effectiveness of the antibiotic. Is it working? Some signs that tells you it isn’t working: persistent abnormal body temperature (hyperthermic or hypothermic), elevated heart rate, low blood pressure, altered mental status, breathing problems, elevated white blood cell count >10,000 mm3)
Monitor and educate about adverse effects:
Remember CLOG
Cardiac issues
QT interval prolonged which can lead to Torsades de Pointes
- Increased chance of this happening if the patient is taking other meds that also prolong the QT interval like antiarrhythmics (Amiodarone, Quinidine), antibiotics (Fluoroquinolones), antidepressants, antipsychotics etc.
Liver problems like cholestatic jaundice
Mainly erythromycin
- Monitor liver enzymes (elevated ALT, AST, ALP, bilirubin)
- Jaundice: yellowing or orange hue to the white of the eyes or skin
- Abdominal pain
- Fatigue
- Dark urine (bilirubin leaking into the urine) and light-colored stool (bilirubin is not leaving the body via the stool like it should but is leaking over into the urine…bilirubin gives the stool its brown color…without it the stool is light colored).
Ototoxicity (toxic to the hearing structures of the ears)
Educate patient to watch out for and report ringing in ears, hearing loss, dizziness, full feeling in the ear
- Usually reversible and can happen with high doses of Macrolides in patients who have altered renal function
GI upset
Due to increased of GI motility
- Mainly occurs with Erythromycin
- Educate to take with food if GI upset develops, but it’s best to take this group without food to encourage high absorption…food can alter absorption
- Take 1 hour before or 2 hour after meals with only water…8 ounces at least
- Not to be taken with acidic drinks like fruit juice or milk because this can alter absorption
Test your knowledge on this material with this free Macrolides quiz.
References:
Center for Drug Evaluation and Research. (2014, February 18). Azithromycin (Zithromax or Zmax) and the risk of potentially fatal. U.S. Food and Drug Administration. Retrieved September 21, 2022, from https://www.fda.gov/drugs/drug-safety-and-availability/fda-drug-safety-communication-azithromycin-zithromax-or-zmax-and-risk-potentially-fatal-heart
(Erythromycin ethylsuccinate) RX only – Food and Drug Administration. Access Data: Food and Drug Administration. (2012, January). Retrieved September 21, 2022, from https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/050207s071lbl.pdf
Vázquez-Laslop, N., & Mankin, A. S. (2018). How Macrolide Antibiotics Work. Trends in biochemical sciences, 43(9), 668–684. https://doi.org/10.1016/j.tibs.2018.06.011